DISSERTATION print copy

LEAD SORPTION FROM INDUSTRIAL EFFLUENTS USING
AGRICULTURAL WASTES: IDENTIFICATION OF THE
BEST METHOD FOR NIGERIA.
BY
LAIYEMO, MICHAEL ADEMOLA
(STUDENT ID: 1123956)
A DISSERTATION SUBMITTED IN PARTIAL FULFILMENT OF THE AWARD OF
A MASTERS OF SCIENCE DEGREE IN ENVIRONMENTAL SCIENCE:
LEGISLATION AND MANAGEMENT
SUPERVISOR: DR. ABDUL CHAUDHARY
SEPTEMBER 2012

Laiyemo,Michael A. 1123956
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DEDICATION
I dedicate this dissertation to my parents Mr Omololu and Mrs Feyisara Laiyemo, for whom
God has used to be my pillar of support during my course of study. Just to let you know that
out of a billion parents, I will choose both of you over and over again and this work would not
have been possible without you. Thank you very much.

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ACKNOWLEDGEMENT
“Instruct the wise and they will be wiser; teach the righteous and they will add to their
learning” Prov. 9: 9.
Most supervisors fix appointments for consultation but an exception is Dr. Abdul Chaudhary
whose door is always opened for students. My greatest appreciation goes to my supervisor,
Dr. Abdul Chaudhary because of his magnificent support and guidance during this
dissertation.
I appreciate the support of my sisters; Kofo, Kemi and especially Lamide who has
significantly been part of my educational progress.
My brothers from another mother; Mayowa Oshin and Godwin Nwokobia, thank you guys for
the moral support, and being there for me in times of need. May God reward you abundantly.
To the almighty God, who has brought me this far in life, continue to guide and protect me in
all my ways of life.

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CERTIFICATE OF AUTHORSHIP
“I, Laiyemo Michael A., hereby certify that:
Each and every quotation, diagram or other piece of exposition which is copied from
or based upon the work of others has its source clearly cited and referenced in the
text at the place where it appears.
All research studies in this report have been carried out by me with no more
assistance from members of the institution than has been specified.
Name: Laiyemo, Michael A.
Signature:
Date: 21st September, 2012

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ABSTRACT
This study demonstrates why Nigeria as a developing country and having series of lead
pollution problems by processing industries should implement a cheap and efficient
technology for lead removal from industrial effluent. The Federal Environmental Protection
Agency (FEPA) set down policies for processing industries to engage in the best available
technology (BAT) during effluent treatment and there has to be reduction of toxic chemicals
to a minimum level before effluents are discharged into receiving waters.
So despite the numerous methods to remove lead from a solution, biosorption technology is
the most cost effective and environmentally friendly because it makes use of reusable low cost
agricultural waste as adsorbent.
In this study, comparative analysis of selected agricultural wastes used in the preparation of
adsorbents for the biosorption of lead from industrial effluent was done. The agricultural
wastes compared are orange peels, sugarcane bagasse, rice husk and maize cob. The study was
performed in order to identify the best agriculture waste in terms of adsorption efficiency and
cost effectiveness that can be introduced in the biosorption of lead from industrial effluents in
Nigeria.
Each selected agricultural wastes was subjected to SWOT and PEST analyses in which the
analyses were based on adsorption capacity of the adsorbent, the adsorption rates, equilibrium
time for lead removal, availability of the agricultural waste in Nigeria, desorption rate of the
adsorbed lead from the adsorbent, the social and environmental impact and finally the political
implications of using the agricultural wastes.
Work done by researchers (secondary data) were used throughout this study and it was
discovered that adsorption capacity of the agricultural wastes differ depending on the
adsorbent treatment, temperature of reaction, pH of the solution, contact time and adsorbent
loading.
However based on the available data, the research showed that modified adsorbents show
better adsorption capacities than unmodified adsorbents. Triethylene-tetramine modified
sugarcane bagasse has the highest adsorption capacity of 313mg/g compared to the other
wastes and further evaluation of the comparative parameters highlighted that triethylene-
tetramine modified bagasse is the best method that can be used in lead biosorption from
industrial effluents in Nigeria.
Keywords: Adsorbent; Agricultural wastes; Biosorption; Lead; Industrial effluent; Nigeria;
Adsorption capacity; SWOT analysis; PEST analysis.

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CONTENTS
Title
Page
ACKNOWLEDGEMENT................................................................................................................3
ABSTRACT.....................................................................................................................................5
LIST OF ABBREVIATIONS...........................................................................................................9
LIST OF FIGURES........................................................................................................................10
LIST OF TABLES..........................................................................................................................11
CHAPTER 1: INTRODUCTION...................................................................................................12
1.1 Background ........................................................................................................................12
1.2 Hypothesis..........................................................................................................................14
1.3 Aim of study.......................................................................................................................14
1.4 Objectives of study..............................................................................................................14
1.5 Scope of study ....................................................................................................................15
1.6 Importance of the study.......................................................................................................15
1.7 Summary of the Report........................................................................................................15
1.7.1 Introduction..................................................................................................................15
1.7.2 Literature Review .........................................................................................................15
1.7.3 Methodology ................................................................................................................16
1.7.5 Conclusion and Recommendation ..................................................................................16
CHAPTER 2: LITERATURE REVIEW........................................................................................17
2.1 Lead and its toxicity ............................................................................................................17
2.2 Sources of lead pollution .....................................................................................................18
2.3.1 The Federal Environmental Protection Agency ...............................................................21
2.3.2 Water pollution in Nigeria .............................................................................................22
2.4 Conventional methods for lead removal from an aqueous solution..........................................24
2.4.1 Ion exchange ................................................................................................................24
2.4.2 Precipitation method .....................................................................................................24
2.4.3 Reverse osmosis ...........................................................................................................24

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2.4.4 Flocculation/Coagulation...............................................................................................24
2.5 Biosorption.........................................................................................................................25
2.6.1 Characterization of the adsorbents..................................................................................27
2.6.2 Preparation of adsorbents for experiment........................................................................30
2.6.3 Biosorption experimental procedure...............................................................................31
2.6.3.1 Kinetic studies ...........................................................................................................32
2.6.3.2 Adsorption isotherm...................................................................................................33
2.6.3.2.1 Freundlich isotherm.................................................................................................33
2.6.3.2.2 Langmuir isotherm ..................................................................................................33
2.6.4 Desorption....................................................................................................................34
2.8 Conclusion .........................................................................................................................37
CHAPTER 3:Methodology............................................................................................................39
3.1 Methodology ......................................................................................................................39
3.2 Analytical Tools..................................................................................................................40
3.2.1 SWOT analysis.............................................................................................................40
3.2.3 Justification in using SWOT and PEST analytical tools ...................................................41
CHAPTER 4: Results and Discussion.............................................................................................43
4.1 Availability of the selected agricultural wastes......................................................................43
4.1.1 Availability of Orange peel in Nigeria ............................................................................43
4.1.2 Availability of Sugarcane bagasse in Nigeria ..................................................................44
4.1.3 Availability of Rice husk in Nigeria ...............................................................................44
4.1.4 Availability of Maize cob in Nigeria ..............................................................................44
4.2 Description of other comparison parameters..........................................................................44
4.2.2 Equilibrium time...........................................................................................................45
4.2.3 Adsorption rate.............................................................................................................45
4.2.4 Desorption rate .............................................................................................................45
4.3 Data collected.....................................................................................................................45
4.4 SWOT and PEST analysis of the selected agricultural wastes used for lead biosorption. ..........48
4.5 Discussion ..........................................................................................................................54
4.5.1 Outcome of the SWOT analyses ....................................................................................54
4.5.1.1 Orange peel...............................................................................................................55
4.5.1.2 Rice husk...................................................................................................................56

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4.5.1.3 Sugarcane bagasse......................................................................................................56
4.5.1.4 Maize cob..................................................................................................................57
4.5.2 Outcome of the PEST analyses ......................................................................................58
CHAPTER 5: CONCLUSION AND RECOMMENDATION.........................................................60
5.1 Conclusion .........................................................................................................................60
5.2 Recommendation ................................................................................................................60
REFERENCES...............................................................................................................................62

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LIST OF ABBREVIATIONS
AAS Atomic Absorption Spectrometer
ATSDR Agency for Toxic Substance and Disease Registry
BAT Best Available Technology
BOD Biological Oxygen Demand
COD Chemical Oxygen Demand
CSTR Continuously Stirred Tank Reactor
EDTA Ethylene diamine tetra-acetic acid
FEPA Federal Environmental Protection Agency
FTIR Fourrier Transfer Infrared Spectroscopy
SEM Scanning Electron Microscopy
SWOT Strength, Weakness, Opportunity and Technology
TOC Total Organic Carbon
PEST Political, Environmental, Social and Technological
UNEP United Nations Environmental Protection
WHO World Health Organisation

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LIST OF FIGURES
Figure Title Page
2.1 Schematic flow diagram showing the biosorption of heavy metals
industrial wastewater using adsorbents…………………………………………36
3.1 Overview of the research study……………………………………………….39

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LIST OF TABLES
Table Title Page
3.1 The template of the SWOT matrix…………………………………………............40
4.1 Work done by researchers on the removal of lead from aqueous solution…………46
using the selected agricultural wastes
4.2 SWOT matrix for orange peel adsorbent used for lead biosorption………………..48
4.2.1 PEST analysis for orange peel adsorbent used for lead biosorption………………..49
4.3 SWOT matrix for rice husk adsorbent used for lead biosorption……………………50
4.3.1 PEST analysis of rice husk adsorbent used for lead biosorption…………………….51
4.4 SWOT matrix for sugarcane bagasse adsorbent used for lead biosorption………….51
4.4.1 PEST analysis of sugarcane bagasse adsorbent used for lead biosorption…………..52
4.5 SWOT matrix for maize cob adsorbent used for lead biosorption……………………53
4.5.1 PEST analysis of maize cob adsorbent used for lead biosorption…………………….54

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CHAPTER 1: INTRODUCTION
1.1 Background
Water is termed a universal solvent because it supports all life forms and it is the most useful
natural resource on earth (Iqbal and Gupta, 2009). Various uses of water include; agricultural
irrigation, household duties, industrial duties, transportation, power application and it can be
used as a method for waste dumping by manufacturing or processing industries (Rashed,
2001).
However, a report by Bartram and Helmer (UNEP/WHO, 1996) discussed that the use of toxic
chemicals and the implementation of agricultural drainage methods introduce contaminants
into the aquatic environment and therefore contribute to the degradation in water quality.
Hence this consequentially affects the aim of obtaining a sustainable socio-economic
development.
Moreover, pollution in water is mainly due to industrial effluents coming out of sewage
treatment plants (Rashed 2001) and of great concern are heavy metals like Iron (Fe), Copper
(Cu), Mercury (Hg), Manganese (Mn), Zinc (Zn), Cadmium (Cd) and Lead (Pb) because they
are the most significant liable for water contamination (Rashed, 2001). Hence they dissolve in
water and bio-accumulate in the food web thereby causing danger to both terrestrial and
ecological health (Alluri, et al., 2007).
There is not a known definition of heavy metals in most peer review reports but Heavy metals
are often described to have densities five times greater than water and they can be found in the
earth’s crust because they are naturally occurring elements (Neustadt and Pieczenik 2007).
But, small amounts of zinc, copper, iron, and manganese are useful to living organisms in
such a way that they act as metalloenzymes but their toxicity is exercised if they are in high
concentration. For these reasons, they are called trace elements (Harmanescu, et al., 2011).
However, lead and cadmium have no usefulness to living organisms but they tend to be toxic
at low concentration when in contact with organisms (Harmanescu, et al., 2011), giving an
indication that the principle hazard of heavy metals lies within the context of exposure to Lead

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or Cadmium (Jarup, 2003). Furthermore, Adebisi and Fayemiwo (2010) discussed the
significance of improved industrialization as partly the cause of environmental pollution
because industrial effluents containing heavy metals are introduced into sewers and water
bodies thereby causing contamination of in the surroundings.
In view of the foregoing, there is a consistent stress on water quality and availability therefore,
a concise regulation of water bodies is necessary. Hence, an irregularity in the standards set
for water protection may be detrimental to both ecological and environmental health (Ibrahim
and abdullahi, 2008).
As part of the regulation set by governments, industrial effluents need to be pre-treated for
heavy metal removal or reduction before they are dumped into the environment (Volesky,
2000). The methods that could be used to remove metals from solutions could be chemical
processes like precipitation, ion exchange process and reverse osmosis but these methods
could be less effective, costly and may need a lot of energy during operations (Saikaew, et al.,
2009).
Consequentially, the technology for metal Biosorption was initiated during 1980s (Volesky,
2001), and according to Saikaew et al (2009), the interest for the development of the
biosorption technology was heightened because there was the need for a more economical and
efficient separation technologies to remove heavy metals from waste water. Hence it is
envisaged to be a promising sustainable development technology where heavy metals are
removed from a solution, because there is a massive growth in the activities of the
metallurgical industries and they contribute to the increase of heavy metals polluting the water
resources (Shafaghat, et al., 2012).
Economically viable biosorption process involves the use of various types of adsorbents
including agricultural wastes. For biosorption process the adsorbent must be low cost,
abundant in the environment, or maybe a by-product or a waste product from an industry.
Therefore, most researchers have engaged in the use of various agricultural wastes in the
removal of heavy metals from solutions because of their availability or reduced cost and their
environmental friendliness (Shafaghat, et al., 2012).

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1.2 Hypothesis
Does adsorption capacity of low cost agricultural wastes differ in removal of lead ion from
aqueous solutions? At which conditions is it most efficient in lead ion removal?
1.3 Aim of study
The aim of this project is to investigate which low cost agricultural waste can best be used as
adsorbent for the removal of lead ion from aqueous solutions in Nigeria.
1.4 Objectives of study
The following objectives have been highlighted to help achieve the aim of the research by
using S-W-O-T and P-E-S-T analysis;
 To characterize the agriculture adsorbent materials to collect their chemical and
physical properties.
 To detect the best conditions for lead ion removal in terms of temperature, pH,
adsorbent loading, and contact time.
 To compare the adsorption capacities of selected low cost agricultural wastes.
 To quantify the adsorption rate of lead ion.
 To determine the potential for lead recoverability.
 To determine the Nigerian legislation and policy that can drive the biosorption
technology.
 To determine the socio-economic and environmental impact of each adsorbent.

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1.5 Scope of study
This study is limited to the application of agricultural wastes as adsorbents to remove lead
present in industrial effluents in Nigeria. Furthermore, comparison will be made between
orange peels, sugarcane bagasse, maize cobs and rice husk for the biosorption technology in
order to determine which agricultural waste’s method is more sustainable for Nigeria.
1.6 Importance of the study
Nigeria like any developing country is constraint with funds, the importance of this study is
therefore to find an environmental friendly way where lead extraction could be achieved
relatively in a cheaper means. By implementing such adsorbent in an industrial effluent
treatment process, it will save cost, energy, reduce carbon foot print and reduce environmental
pollution.
1.7 Summary of the Report
This section discusses the format and stages involved in order to achieve the aim and
objectives of this study. The stages include: (i) Introduction (ii) Literature review (iii)
Methodology (iv) Results & Discussion and (v) Conclusion and Recommendation.
1.7.1 Introduction
The background information leading to the study is discussed in this chapter, the importance
and scope of this study is also highlighted in this chapter. Also incorporated in this chapter are
the aims and objectives of the study.
1.7.2 Literature Review
This chapter discusses the relevant studies on the subject by analysing peer reviewed papers
and case studies relating to the research. Studies on lead and its toxicity, sources of
contamination, biosorption method of removal, and studies on the adsorbent characterisation
are evaluated in this chapter in order to meet the aim and objectives set out in chapter 1. In
addition, the area of study and the required regulation are discussed.

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1.7.3 Methodology
The methods used to gather information and interpret the data used for the research objectives
are discussed in this chapter. The justification for opting for such method is presented and also
the reasons for nominating the scope of study are discussed.
1.7.4 Results and Discussion
This chapter highlights the results of findings from the study of literature review and critical
analysis and discussion is carried out for the intention of identifying the best agricultural
waste for biosorption method.
1.7.5 Conclusion and Recommendation
A summary of the findings gotten from the research process is presented in this chapter. The
possibility and areas of further research is highlighted in this chapter and recommendations
are proposed in other to achieve the desired option for the study.

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CHAPTER 2: LITERATURE REVIEW
2.1 Lead and its toxicity
In physicochemical terms, lead is described as a soft metallic element having an atomic
number of 82, coupled with density of 11.34 g/cm3 and melting point of about 327.5 °C
(Pokras and Kneeland, 2008). The occurrence of lead in the environment is either through its
natural existence or by man’s anthropogenic activities which will be discussed later in this
report.
Lead was reported to be amongst the most investigated industrial and environmentally
harmful substance because its usage for industrial purposes was dated as far back as the
Roman Empire era (Gidlow, 2004). Also, Graeme and Pollack (1998) argued that; “lead
poisoning extracted from boiling grape juice in lead pots and from storing and curing
beverages in lead-lined containers may have contributed to the fall of the Roman Empire”.
Therefore as illustrated above, the toxicity of lead has been a prevalent issue since the
beginning of civilisation.
Although, some heavy metals are seen to be essential for living organisms at low
concentrations but studies have shown that even at low concentration, lead is highly toxic.
Even in recent times, the World Health Organisation (WHO, 2010) reported that 0.6% of the
worldwide threatening diseases are due to lead toxicity and as part of the health concerns,
WHO on four different occasions was able to carry out health risk assessment on lead
contaminated food in 1972. Various workshops for guidance on lead poisoning were also
initiated by WHO and these have been going on for over 38 years.
According to Agency for Toxic Substances and Disease Registry (ATSDR, 2007), the toxicity
on humans depends on various conditions like age, diet and the duration of exposure.
Furthermore, ATSDR discussed lead and dietary experiments involving adults who were
exposed to lead just after eating and it was discovered that the lead absorbed into their
bloodstreams was 6%. This is a very low rate compared to adults that have not eaten for a day,
and have about 60 to 80% absorption rate of lead into their blood stream.

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As a result of lead absorbed into the blood stream, the erythrocytes are the first target for
absorbed lead in humans and then it distributes all over the body tissues and the bone marrows
where almost all the absorbed lead is deposited. Studies have shown that lead conjugates to
give glutathione and up to 99% are excreted in adults but only 32% are excreted in children
giving an indication that children are more prone to lead poisoning. However, continuous
exposure to lead results in lead accumulation in the body either in adults or children and
increase in blood lead concentration will result in chronic lead poisoning (Kimani, 2005).
Various effects of lead poisoning in humans have been observed through experiments, Pokras
and Kneeland (2008) reported that absorbed lead replaces the body essential metallic elements
like calcium, magnesium and zinc thereby disrupting the usual body metabolism.
Furthermore, they explained how lead toxicity affects nervous system, giving rise to stomach
pain, and also causing anaemia due to reduction in red blood cells when the bone marrow is
being attacked. Additionally mental developments in children have been affected negatively
by low level of lead at about 10µg/dl because it reduces their intelligence and also distorts
coordination in children (Johnson, et al., 2009).
Lead toxicity was further illustrated by Zaki et al (2010) after exposing 8 Marino sheeps to
lead and the animals showed symptoms of depression, inflammatory eyeballs, blindness, and
reduction in their testosterone level. Also, Wister rats treated with dosage of lead showed
kidney malfunction, loss of appetite and reduction in growth rate (Missoun, et al., 2010).
Hence, by extrapolation these symptoms could also be linked to human poisoning by lead.
Basically the toxicity of lead goes a long way in affecting the body functions and as the saying
goes prevention is better than cure so instead of focussing on the treatment for affected
people, the best solution is to prevent lead contamination in the environment by limiting the
amount of lead fed into the environment.
2.2 Sources of lead pollution
As discussed earlier, lead exists in the environment by its natural existence on earth or by
man’s anthropogenic activities. But studies have declared that most of its pollution is caused
by anthropogenic activities. According to a report by Weiss et al (1999), the global

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anthropogenic emission rates of lead is about 332 × 109 g/year and the global natural
emissions sum up to about 12 × 109 g/year. Comparing the two values, it is obvious that
human activities, contribute more to lead’s existence in the environment.
Furthermore, Weiss et al (1999) argued that by calculating interference factor (IF) of heavy
metals which is the ratio of global anthropogenic emission rates to global natural emission
rates, lead was discovered to have a high interference factor compared to the rest of the heavy
metals.
Leaded petrol was a major cause of lead pollution in the society but most countries have put a
stop to its use as part of lead pollution controls (Makokha, et al., 2008). Also, house paints
containing lead have been recently phased out in most countries because it was discovered
that lead contamination occurs when applying or removing the paint on the walls (WHO
2010).
Nevertheless, environmental contamination by lead is still on the rise due to increase in
industrialization in countries, especially developing countries. Despite the various ways of
lead contamination, contamination caused by effluents coming from process industries
contributes immensely to lead pollution (Nasrullah, et al., 2006).
However, this study is limited to the presence of lead in aqueous solution, and in practical
sense aqueous solution can be interchanged for industrial effluents. Manufacturing industries
that participate in battery production, metal plating, paint production, mining and smelting
contribute immensely to lead pollution (Gupta, et al., 2001) because the industrial effluents
coming out from these industrial processes are dumped into surface waters without adequate
treatments to remove the heavy metal (Nasrullah, et al., 2006).
Apparently, the constituents of these effluents are the dissolved part of the raw materials used
in production and also its by-products that are also referred to as waste product. For instance
lead smelting which involves separating lead from its ore (primary smelting) or from lead
products (secondary smelting), is done using a blast furnace in the reactor thereby producing a
high temperature during the process (World bank group, 1998). Hence, cooling water is used

20
during the production process which will in turn be discarded as waste water containing lead
and also, the removal of air pollutants by water scrubber solution contributes to the waste
water generated (Woodard & Curran, 2006).
Furthermore, Malakootian et al (2008) reported that pigments are one of the primary raw
materials during paint production and these pigments are made up of lead compounds so
consequently, the effluent from the paint production process also contributes to the
environmental contamination of lead.
Another illustration demonstrating sources of industrial effluents that causes lead pollution is
the waste water produced during the manufacture of lead-acid batteries. The stages in the
battery production that produces most waste water are the pasting process, the electrode
developing process and washing of the manufactured lead-acid batteries (Woodard & Curran,
2006). However these waste waters are discharged as effluents from the waste water treatment
plants into the river or sewers, and if not properly discarded by reducing the level of lead
content to the required amount set by regulations, there will be contamination of the food
chain in the environment because lead is non-biodegradable in the environment but ironically
it undergoes a process called bio-magnification (Alluri, et al., 2007).
So it is highly desirable to carry out a pre-treatment process on the waste water in order to
remove or reduce the lead present in the waste water before waste water treatment takes place.
2.3 Nigeria
Nigeria is a country situated in the western part of Africa on a coastal plain however, its size
of approximately 923,768 km2, and its population of 170 million made it known to people as
Africa’s most populous country (UNEP/OCHA, 2010). Furthermore, Nigeria’s geography is
diverse in nature due to its location, expanse and specific features. The tropical rain forest is
seen along the coast of the country and the northern region is known to have the Sahel
climatic condition (Ayinde, 2010).

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Hence, water resources is in abundance in Nigeria but not equally distributed and this can also
be attributed to the fact that there is high precipitation of about 3,000mm yearly in the south
eastern part and there is reduction in the annual precipitation in the northern part of the
country which is averagely 500mm yearly. Ironically, while there is frequent flooding in the
southern parts of Nigeria, the northern parts experience extreme water shortages (Anukam,
WHO/UNEP, 1997). As discussed by Okunola and Ikuomola (2010), the land which
Nigerians thrive on is richly blessed and also, the climate is quite favourable for the
production of different types of food and cash crops like maize, rice, cassava, cocoa, orange,
rubber, sugarcane and cotton.
Also the abundance of some natural resources like crude oil, natural gas, coal, bauxite, lead,
tin, gold, salt, kaolin etc. are not farfetched. The minerals present in Nigerian soil are mined
on regular basis and various farming activities coupled with agriculture are predominantly
means of lively hood amongst the Nigerian people (UNEP/OCHA, 2010).
However, even with the abundance of natural resources and good climatic condition, Nigeria
still has the problems of environmental pollution, poor technological know-how, and financial
constraints. These problems persist even with the drive of increasing industrialization in the
country, and these have negative impacts on the socio-economic and environmental sectors
within the country.
2.3.1 The Federal Environmental Protection Agency
The Federal Environmental Protection Agency (FEPA) was introduced by the Nigerian federal
military government in 1988 for the purpose of overall environmental protection in Nigeria.
Various duties and responsibilities that were assigned to this body include the prevention and
the control of emitting dangerous and hazardous substances to air, water and soil, it also
functions as the national body that get involves in international environmental activities with
other countries or international bodies. Setting standards for emissions into air, water and
noise pollution is also a major function of FEPA and enforcing these standards by FEPA is
also required by law (Ekubo and Abowei, 2011).

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FEPA was able to set out regulations for industrial effluents and these are reflected in The
Federal Environmental Protection Agency Act (Cap 131 LFN) (Effluent Limitation)
Regulations 1991.
Section 1(1) of the act states that; “Every industry shall install anti-pollution equipment for
the detoxification of effluent and chemical discharges emanating from the industry”.
Section 1(2) compliments paragraph 2 in terms of technology by stating that; “An installation
made pursuant to paragraph (1) of this regulation shall be based on the Best Available
Technology (BAT), the Best Practical Technology (BPT) or the Uniform Effluent Standards
(UES)”.
Section 3(1) of the FEPA Act 1991 states that; “An industry which discharges effluent shall
treat the effluent to a uniform level as specified in Schedule 2 to these regulations to ensure
assimilation by the receiving water into which the effluent is discharged”.
According to Schedule 2 of the FEPA Act 1991 in the effluent limitation guidelines in Nigeria
for all categories of industries, the lead limit for discharge into surface water is less than 1mg/l
and that for specific industries like automotive battery industries, metal working plating and
finishing industries, their lead limit is 0.01µg/l, for petrochemicals, their lead limit is 0.05µg/l.
These regulations are simple, straight forward and if not violated it would help to protect the
environment from industrial waste water to a large extent, but the problem of heavy metal
contamination due to industrial effluents still persists despite the set regulations. Further into
this study, discussions will identify where the problem lies and possible solutions will be
nominated.
2.3.2 Water pollution in Nigeria
Pollution in the aquatic water affects both rural and urban areas in Nigeria, because most
industries in Nigeria decide to locate their factories on river banks in order to have easy access
to industrial effluent disposal through river dumping and they do not consider the effects this
would have on aquatic life. The aquatic environment in Nigeria can be considered as a home

23
to various animals like fishes, sea turtles, whales, crocodiles, crustaceans, snakes etc. and can
also be a source of food within the entire ecosystem. Industries considered to be prominent for
water pollution in Nigeria are, petroleum industries, mining industries, plastics industries,
paint industries, textile industries, pharmaceutical industries, iron and steel industries, and
distillery industries (Anukam, WHO/UNEP, 1997).
A part of the motivation for this study is because there have been various reports on lead
contamination in Nigeria, for instance the joint UNEP/OCHA environment unit (2010) carried
out an emergency investigation in Zamfara state which is in the northern part of Nigeria. The
investigation was initiated by an international medical relief organisation called Médecins
sans Frontières because it was discovered that unexpected deaths occurred amongst the people
living in that area especially amongst children under five years old.
It was revealed during the investigation that the deaths were as a result of acute lead poisoning
which was caused by environmental contamination from processing of gold gotten from an
ore rich in lead and further studies discovered that the 10 µg/dl limit of lead in drinking water
set by WHO and the federal government was highly exceeded. Furthermore, ponds were also
found to be contaminated by lead and other investigations made the joint UNEP/OCHA
conclude that the lead contamination was as a result of lead processing.
In view of the forgoing, Ogunseitan and Smith (2007) reported that the mean blood
concentration of lead amongst children acquired from different locations in Nigeria to be 11.4
– 25 µg/dl and this level is very unacceptable according to the 10µg/dl level set by the World
Health Organisation (WHO). They further discussed industrial sources as partly the cause of
such high level of blood contamination in children.
Considering the above reviews, it is obvious that a major problem in Nigeria is the
contamination of lead through processing and industrial uses. However, as discussed earlier
waste water treatment is a major factor aiding the pathway through which lead gets into the
environment so therefore lead removal from effluent is inevitable and Nigeria being a
developing country with financial constraints need a cheaper and effective means of lead

24
removal. Nevertheless, there is the need to discuss the different techniques of lead extraction
from a solution and also give reasons why biosorption is a viable and sustainable method for
Nigerian use. Furthermore, discussion will progress into the various agro wastes for
biosorption and the best agro waste will be highlighted.
2.4 Conventional methods for lead removal from an aqueous solution
The conventional methods used in lead removal from solutions may involve chemical,
physical and biological processes, a few of the are explained in the subsections below;
2.4.1 Ion exchange
A bed of resins is used to selectively remove undesired ions passing through the resin fitted
column and these ions can therefore be recovered from the resin. However there are
limitations in using such method because studies have discovered that other waste water
materials have destructive effects on the resins and also considered as a disadvantage is the
high cost of acquiring resins (Fu and Wang, 2011).
2.4.2 Precipitation method
It involves using alkali agents to precipitate soluble heavy metals from a solution in which an
insoluble metal compound is formed. The usual alkali precipitating agents are caustic soda,
lime and magnesium hydroxide, whereby the metal is precipitated as a hydroxide. Despite
being an easy technology, it is not effective in removing lead ions in the presence of
complexing agents, it requires pH adjustment so there is increase in cost due to purchase of
pH adjustment chemicals and the quantities of sludge formed after precipitation is massive
thereby giving rise to disposal problems (Eisazadeh, 2008).
2.4.3 Reverse osmosis
This technology involves passing the aqueous solution through a semi permeable membrane
and the unwanted ions are being block from passing through the membrane. However, its
limitation is that it requires a high energy to power the pump for pressure input and to restore
the degrading membrane (Fu and Wang, 2011).
2.4.4 Flocculation/Coagulation
This employs the use of ferric salts like ferric chloride to precipitate the metal ions but this is
achieved only after a polymer was used to separate oil from the solution. However, this

25
method is effective when dealing with low volume of solution and a massive sludge is
produced which gives rise to disposal problems (Patoczka, et al., 1998).
In view of the foregoing some of the processes are efficient but they either need a lot of
energy to meet their required demands or they operate at increased cost, and some are not
effective in extracting metal ions. Moreover in modern times, industries are required to engage
in sustainable development practices in their respective organisations, so an economically
viable and environmentally friendly method of lead removal from industrial effluents was
initiated and this is explained in the next section.
2.5 Biosorption
Most peer reviews acknowledged biosorption as the best method for heavy metal removal
from aqueous solution in terms of cost effectiveness and environmental friendliness because it
makes use of naturally available materials or perhaps materials that are considered as waste to
remove heavy metals present in industrial effluents. It is of big advantage to discover a
process of employing naturally occurring wastes to reduce heavy metal contamination because
these wastes are inexpensive to acquire and despite being termed wastes, they term to be
useful in environmental protection.
Biosorption method has a great advantage over the other conventional methods in the sense
that it has high removal efficiency, the method of removal is low cost, it produces low sludge,
metal recovery and regeneration of the adsorbent is possible (Yeneneh, et al., 2011).
The technique of biosorption as described by Das et al., (2008) is that it involves a sorbent
which is the solid medium and the liquid medium which is the aqueous solution, and also
present in the liquid medium is the dissolved metal ion. The metal ion is removed from the
liquid medium due to the fact that the sorbent has a great attraction for the metal ions.
However Das et al., (2008) further explained that various mechanisms are used during the
sorption process depending on the sorbent and the process stops when equilibrium is attained
between the adsorbed metal ion and the metal ion which is remained in the liquid medium.

26
Different sorbents can be used for biosorption, they include biomasses such as; bacteria, fungi,
agricultural wastes, algae and yeast (Wang and Chen, 2009), but the focus of this study is
limited to Biosorption using agricultural wastes.
The mechanism behind using agricultural wastes as sorbent is due to the fact that these
agricultural wastes contain carbonyl, phenolic, amido, amino, acetamido or hydroxyl
functional groups on their surfaces and these groups have affinity for the positively charge
metal ions to form complex compounds (Sud, et al., 2008). And indeed, the presence of such
variety functional sites enhances the ability for different metal bindings by adsorption,
chelation and ion exchange (Ogali, et al., 2008).
2.6 Agricultural wastes as adsorbent
As discussed by Yeneneh et al (2011), the most viable agricultural wastes for heavy metal
removal should be eco-friendly, their chemical composition must be specific for the purpose
of binding with metal ion, they must be abundant in nature, low cost, and they must be very
efficient in heavy metal removal. Various researchers have demonstrated the competence of
agricultural wastes in lead uptake at different conditions.
Studies have shown that activated carbon treated Korean mandarine orange peel is a
promising agricultural waste that can be used to remove lead ion and this was demonstrated by
Park (2011). Using adsorbent weight of 0.2g at a concentration of 41.4 mg/l, at temperature of
30ºC and pH 5 gave lead ion adsorption rate of 44.2%. The best adsorption rate was 99.9% at
pH 9.
Sometimes, these adsorbents are modified to increase their adsorption rate. For instance,
Martín-Lara et al (2010) carried out experiments to remove lead ion from aqueous solution
using treated and untreated sugar cane bagasse. The sugar cane was treated with hydrogen
tetrasulphate (V1) acid to increase the sorption capacity for lead and to remove the soluble
substances on the surface. The overall result gave lead to be well removed by the treated sugar
cane bagasse with sorption capacity of 7.297 mg/g, and the untreated bagasse with sorption
capacity of 6.366 mg/g at temperature of 25 °C and pH 5 (Martín-Lara, et al., 2010).

27
Usually all experiments for metal adsorptions are executed with variations in adsorbent
loading, pH, contact time or temperature and the rate of adsorption is calculated using the
Langmuir or Freundlich isotherm.
Furthermore, Elham et al (2010) investigated the used of rice husk to remove zinc and lead
ions with variations in contact time, adsorbent load, and pH value of waste water. Results
gave 19.617 and 0.6216 mg/g, respectively as the adsorption capacity for zinc and lead and
the adsorption was strongly enhanced at pH 7 for zinc and pH 9 for lead. The maximum
percentage of removing lead was 96%.
Another experiment done to remove lead from an aqueous solution and effluents from battery
and paint industries was performed by Opeolu et al (2009) using maize cob as an adsorbent.
Dowex an ion exchange resin was added to another portion of the effluents as control
parameter. The experiment was analysed using Langmuir isotherm and it gave the removal of
lead to be 99.9% from the battery effluent and 47.38% with the effluent that was treated with
Dowex. However the removal rates for lead in paint effluents were 66.16% and 27.83% for
the Dowex controlled effluent.
Although these adsorbents are relatively cheap and readily available, Khan et al (2004)
discussed the importance of comparing the adsorbents in terms of cost and explained that
costs is being determined by the adsorbents degree of processing and their availability to the
area of research. Furthermore Khan et al (2004) emphasized that enhancement in their ability
to adsorb metals may compensate for the costs of any modification done on the adsorbent. So
therefore it is paramount to study the sources of these adsorbents and their ability to remove
heavy metals from aqueous solutions.
2.6.1 Characterization of the adsorbents
Sometimes, it is important to subject some agricultural wastes to chemical treatment before
being used as adsorbents. Untreated wastes may not be effective in removing heavy metals
and may also distort the physicochemical properties of the aqueous solution by discharging its

28
organic soluble compounds into the solution and thereby increasing its chemical oxygen
demand (COD), biological oxygen demand (BOD) and total organic carbon (TOC).
Consequently, the increase in these physicochemical properties will reduce the oxygen level in
the solution and this will be detrimental to the aquatic ecosystem (Feng and Guo, 2012).
Nonetheless modified adsorbents can enhance the efficiency for lead removal, but there
should be consideration on the cost of acquiring chemicals for such modification and the cost
of methods used because the main purpose of using adsorbents is to achieve a low cost
method for biosorption. However, characterization studies on the changes in properties of the
modified adsorbents should be carried out to ascertain if it is necessary to modify the
adsorbent or to use it in its natural form (Ngah and Hanaﬁah, 2007).
Hence since the basic characteristics of adsorbents that favour and increase the efficiency for
metal binding include large surface area, porous structure, increased adsorption capacity and
an activated surface (Daffalla, et al., 2010), there should be studies on these characteristics to
achieve the aim of low processing cost (Ngah and Hanaﬁah, 2007).
Feng and Guo (2012) discussed the necessity to modify orange peels for adsorption purpose.
The constituents of orange peels which are; cellulose, lignin, pectin and hemicellulose where
reported to contain methyl esters and are known to have a no effect on metal binding.
However, due to findings that carboxyl groups enhance metal binding, the orange peels can be
treated with a base like sodium hydroxide to give a carboxylate functional site to facilitate
metal binding. Additionally, treating the orange peel with calcium chloride is credible because
calcium precipitates polysaccharides such as pectin if the contain carboxyl groups in them and
therefore make the pectin insoluble.
Furthermore, modification of orange peels using sodium hydroxide and calcium chloride by
Feng and Guo (2012) changed the surface morphology of the peel, and an indication for an
increased adsorption capacity was noticed because the structure of the modified orange peel
was uneven and porous compared to the natural orange peel. The surface areas for the
modified orange peel and the natural orange peel were 1.496m2/g and 0.828m2/g respectively.

29
The larger surface area provides larger binding sites for the metal ions, hence adsorption
experiment by Feng and Guo (2012) gave a 30% increase in adsorption rate of lead (Pb2+)
after modifying the orange peels.
Similarly, Yeneneh et al (2011) investigated the role played by chemical modifiers, heat and
size on both rice husk and sugarcane bagasse. The chemical modifiers where chosen
according to the functional site that will be fixed to the adsorbents, and the adsorbents where
treated with 0.1M potassium hydrogen phosphate and 0.1M sodium oxalate at a temperature
of 800 °C for 24 hours. As part of the adsorbent characterisation, the natural and treated rice
husk and sugarcane bagasse where grounded and sieved to particle sizes ranging from (500-
1000µm) to (45-63µm) and different lead removal experiments where carried for each natural
and treated adsorbents. To test for the effect caused by thermal modification, two grams of the
treated adsorbents were burned in a furnace at a temperature of 700 °C and analysed with
Scanning Electron Microscope (SEM), and Fourrier Transform Infra-Red Spectroscopy
(FTIR).
Yeneneh et al., (2011) discovered that potassium hydrogen phosphate increased the efficiency
of rice husk in removing lead ion with the removal capacity of 87.53 mg/g and sodium oxalate
gave 75.40 mg/g as the removal capacity. However, the treated sugarcane bagasse gave a
capacity of 100mg/g when potassium hydrogen phosphate was used as a modifier and sodium
oxalate treated sugarcane bagasse gave 98.53 mg/g removal capacity.
Additionally, it was also ascertained that particle sizes play a big role in lead uptake from a
solution because it was discovered that the smaller particle sizes ranging from 45-63µm for
both adsorbents gave a higher sorption properties compared to the bigger adsorbents sizes.
This was due to the fact that surface area and the affinity for metal binding increases with
decrease in size and obviously, there will be increase in the sorption capacity. The thermal
modification also increased the surface area for both adsorbents with the improvement of the
surface morphology and there was also increase in the roughness of the surfaces, hence
sugarcane bagasse and rice husk gave lead removal efficiencies of 84.1% and 80.5%
respectively.

30
2.6.2 Preparation of adsorbents for experiment
Besides pre-treatment, processing adsorbents for biosorption of heavy metals takes almost the
same pattern for all adsorbents as described by most researchers. For instance the biosorption
experiment was carried out by El-Said (2010) for lead ion removal using rice husk and rice
husk ash, the rice husk was gotten from a rice mill factory and they were grounded to smaller
particles in order to increase its surface area. Furthermore, the particles were sieved to specific
sizes of 0.180, 0.355, and 0.855 using mesh sieves of those particular sizes.
Following the particle preparation, distilled water was used to wash the particles to remove the
impurities present and then the particles were dried in an oven at about temperature of 100 ºC.
The heating of the particle stopped until a constant weight was achieved, this ensured that the
particles were free of all impurities. The prepared absorbent was then stored for further use
during the Biosorption experiment. However, El-Said (2010) further explained that the rice
husk ash was prepared from the dried rice husk by heating it in an oven at a temperature of
600 ºC for about three hours.
Similarly, the preparation of modified sugarcane bagasse for the removal of lead ion from an
aqueous solution was discussed by Osvaldo et al (2007). The bagasse was dried in an oven at
a temperature of about 100 °C for 24hours and the dried bagasse was grounded and sieved
with 10, 30 45 and 60 mesh sizes. Furthermore, distilled water was used to wash the grounded
adsorbent and simultaneously being stirred at a temperature of 65ºC for about an hour and
dried again in an oven.
This procedure prepares the bagasse for the adsorption process. However, further processing
is necessary to develop a modified sugarcane bagasse. Osvaldo et al (2007) treated the washed
and dried adsorbent with succinic anhydride, 1M of acetic acid, 0.1 M of hydrogen chloride,
95% ethanol and distilled water were added to the solution, and then dried in an oven for
30mins at a temperature of about 100 ºC after all these procedure, the adsorbent was ready to
be used for the biosorption process.

31
2.6.3 Biosorption experimental procedure
Various researchers have carried out biosorption experiments and usually the procedures are
similar in the sense that the primary motive for the experiment is to bring both the adsorbent
and the metal ions together so that adsorption can take place. However, the adsorbent
preparation like granulation, washing and drying is highly needed for easy and accurate
experiment.
Usually, the adsorption experiment is carried out at different circumstances, for instance it
could be carried out at different pH, temperature, adsorbent loading and contact time.
A detailed example of such research was carried out by Elham et al., (2010) in which rice
husk was used to extract lead ion from industrial wastewater. The preparation of the rice husk
began the experimental procedure; the husks were washed with distilled water and dried at a
temperature of 100ºC in an oven.
The lead ion concentrated solution was obtained from dairy waste water and the initial
concentration of the lead ion before adsorption was determined using an atomic absorption
spectrometer (AAS). Also, to carry out the experiment at different pH, the pH adjustment was
done by adding either 0.1 M HCl or 0.1 M NaOH to the initial pH of the solution. The HCl
reduces the pH and the NaOH increases the pH level of the solution and however the pH
ranging from 2-9 was obtained for the process.
30 ml of the waste water was made to be in contact with different adsorbent weights ranging
from 0.5 to 3grams and also, the contact time was varied between 5 to 70 minutes. The reason
for these variations is to study the effects of the varying parameters on lead ion extraction by
rice husk.
Furthermore, the adsorbent and the wastewater were kept in 100ml beaker and shaken
rigorously for the specific required time of observation. Afterwards, the solution was filtered
using a filter paper and the solution was analysed using the AAS to determine the lead ion
concentration remaining in the solution and obviously to determine the amount of lead ion
adsorbed by the adsorbent.
Elham et al (2010) calculated the metal ion adsorbed with the formula below;

32
% Adsorption:
Ϲo − Ce
Co
× 100 , where Co is the initial concentration of lead ion in solution
before adsorption in mol/m3 and Ce is the equilibrium concentration or the final concentration
of lead ion in the solution after adsorption in mol/m3.
Furthermore, the amount of lead ion adsorbed per kilogram of the rice husk at equilibrium was
calculated as;
qe =
(𝐶𝑜 – 𝐶𝑒)𝑉
𝑚
, where qe is the adsorbed lead ion on the surface of the adsorbent in mol/Kg
adsorbent, V is the volume of waste water or metal solution in m3, m is the weight of
adsorbent used for the particular experiment in Kg, Co is the initial concentration of lead ion
in solution before adsorption and Ce is the final concentration of metal ion in the solution.
To get a better understanding of the experimental results and to characterize the efficiency of
an adsorbent, the kinetics sorption has to be studied (Abia and Asuquo, 2006). Graphs of
percentage lead ion absorbed are being plotted against their corresponding values varied
within the parameters such as contact time, pH, and absorbent loading.
For instance, Elham et al (2010) discovered that 60% of lead was removed after 5 minutes and
equilibrium adsorption capacity of 49% was achieved after 60 minutes. Similarly, a graph of
metal adsorbed and adsorbent weight was plotted by Elham et al (2010) and it was easy to
interpret the rate of adsorption in relation to adsorbent loading.
2.6.3.1 Kinetic studies
There are different models that can be used to assess the kinetics of adsorption process but the
most widely used are the Lagergren’s pseudo-first-order rate or the pseudo-second –order rate
equation.
Pseudo-first-order rate equation is expressed as;
ln (1-qt/qe) = -K1t, where qt is the amount of metal ion adsorbed per gram of the adsorbent
at any time t (mg/g), qe is the amount of metal ion adsorbed at equilibrium (mg/g) and K1 is
the pseudo-first-order rate equation constant (Saikaew, et al., 2009).

33
The pseudo-second –order rate equation is expressed as t/qt = (1/K2qe
2) + (t/qe), where qt is
the amount of metal ion adsorbed per gram of the adsorbent at any time t (mg/g), qe is the
amount of metal ion adsorbed at equilibrium (mg/g), and K2 is the pseudo-second –order rate
equation constant (Saikaew, et al., 2009).
2.6.3.2 Adsorption isotherm
To analyse the adsorption capacity of adsorbents, the equilibrium studies are required and the
equilibrium correlations between the adsorbent and the metal ion are justified using adsorption
isotherms. Moreover, Freundlich and Langmuir adsorption isotherm are often used to show
the relationship between the amount of the adsorbed metal and the amount of the metal
remaining in the solution at a particular temperature and at equilibrium (Hussein, et al., 2004).
2.6.3.2.1 Freundlich isotherm
The adsorption on heterogeneous surfaces is explained using Freundlich Isotherm, and the
equation for the Freundlich isotherm is;
logqe = log𝐾 +
1
𝑛
log𝐶ₑ , where qe is the amount of metal ion adsorbed by the adsorbent
at equilibrium (mg/g), Ce is the concentration of the metal ion at equilibrium (mg/l), K and
1
𝑛
are the Freundlich isotherm constants and they are the values of the intercept and the slope
respectively determined from the linear curve graph of logqe against logCe (John, et al.,
2011).
The K value is related to the adsorption capacity in the sense that a larger K value indicates a
high adsorption capacity and the
1
𝑛
value describes the change in the effectiveness of the
adsorbent if the equilibrium concentration is changed (Mamman, et al., 2011).
2.6.3.2.2 Langmuir isotherm
The Langmuir isotherm is suitable for single layer adsorption on the adsorbent surfaces
containing adsorption sites that are similar (Karaca, et al., 2010).
Langmuir isotherm is described by the equation;

34
𝐶ₑ
𝑞ₑ
=
1
𝑞˳𝐾˳
+
𝐶ₑ
𝑞˳
, Where qe is the amount of lead extracted at equilibrium (mg/g),
q˳ is the maximum adsorbent uptake capacity during saturation (mg/g), Ce is the equilibrium
concentration of metal in the solution (mg/l), and K˳ is the Langmuir constant (John, et al.,
2011).
If the graph of
𝐶ₑ
𝑞ₑ
against Ce is plotted and it gives a linear curve, then the adsorption
approaches the Langmuir model. Furthermore, the slope of the curve is the q˳ value which is
the maximum capacity for lead uptake by the adsorbent and the K˳ is determined as the
intercept of the curve (Mamman, et al., 2011). The Langmuir isotherm is widely acceptable
due to the fact that it is used to quantify the adsorption capacities of agricultural wastes so it is
considered the most useful in the course of this study (Dos Santos, et al., 2010).
2.6.4 Desorption
Desorption is a process whereby the lead ion saturated adsorbent is subjected to treatment in
order to separate the adsorbent from the lead ion. In other words, the adsorbent is regenerated
for further use and the metal ion is recovered from the liquid medium. The application of
desorption in an industry practising the biosorption process helps in keeping the cost of
processing down and imbibes the phenomenon of sustainable development practice in such
industry because the metal can also be recovered and used for other purposes.
However, biosorption process is described to be a complete economically viable process for
industrial use if it is possible to regenerate the used adsorbent for further biosorption
processes. (Acheampong, et al., 2009). Basically, the desorption process makes use of a
suitable solution to wash the saturated adsorbent, in which a suitable solution is that which is
selective in allowing the metal ion to dissolve in the solution and an equilibrium is achieved
between the dissolved metal ion and the ions that are still adhered to the adsorbent (Volesky,
2000).

35
In identifying a suitable solution for desorption, there must be considerations on the type of
adsorbent, the mechanism behind the biosorption process and the solution must be
environmentally friendly, low cost and must not have a destructive nature towards the
adsorbent. Solutions that could be used for desorption include acids, chelating agents, and
alkalines (Acheampong, et al., 2009). After the desorption process, there will be few lead ions
that will still be present on the adsorbent surface but the advantage of desorption is that it
provides free active sites for metal biosorption to take place after the adsorbent had been used
on the first instance.
A few literature review on desorption of heavy metals exists but Akissi et al (2010) took part
in desorption study after sawdust was used as an adsorbent to remove Pb (II) from aqueous
solution. The solutions tested for desorption include; double distilled water, ethylene di-amine
tetra acetic acid (EDTA), sulphuric acid (H2SO4), calcium chloride (CaCl2), sodium chloride
(NaCl), 0.2 M hydrochloric acid (HCL), and nitric acid (HNO3).
The mixtures of the metal ion bounded adsorbent and the desorption solutions were shaken
vigorously for about 45 minutes and then filtered, the filtrate which is the saw dust was
analysed to determine the amount of lead ions left after desorption. However, the experiment
was repeated four times using the same adsorbent.
Akissi et al (2010) reported the desorption ratio to be calculated as the amount of lead ion
desorbed/amount of lead ion adsorbed.
The result of the experiment showed that EDTA had the highest percentage of desorption of
about 77.29% and the lowest rate of desorption was double distilled water which was 2.11%.
Further adsorption with the same sawdust reduced the amount of lead ion adsorbed due to the
fact that some lead ions where still present after the desorption process.

36
2.7 Industrial application of the biosorption method for lead ion removal from an
aqueous solution
Metal ion
on
Metal ion
Acid or Base
solutionpH control
Adsorbent
vessel
CSTR
Temp
guage
pH
meter
Desorption
solution
Filtration
tank
CSTR
Heavy metal
solution tank
Treated waste
water tank
Filtration
tank
Temp.
guage
pH
mtr
ee
e
Adsorbent
recycle
Figure 2.1: Schematic flow diagram showing the biosorption of heavy metals from industrial wastewater using
adsorbents
Source: Igwe andAbia (2006)

37
The above flow diagram is the schematic representation of the industrial application of the
biosorption method by removing metal ions from industrial wastewater using an adsorbent as
discussed by Igwe and Abia (2006). It can be seen from the diagram that the wastewater
containing the metal ion for an example, lead ion is introduced into the reactor and also the
adsorbent is introduced into the continuously stirred tank reactor (CSTR). The adsorbent could
have been pre-treated or modified if necessary, and after the introduction of both wastewater
and adsorbent into the CSTR, they are both stirred continuously for a period of time in the
reactor and the adsorption of the metal ion onto the adsorbent takes place. After equilibrium
has been attained for the adsorption process, the adsorbent becomes saturated and no more
metal ion is adsorbed on its surface. The solution goes into the filtration tank and it is filtered
thereby separating the adsorbent saturated with metal ion from the wastewater, the resultant
wastewater is collected in a tank and the adsorbent is ejected into another CSTR for the
purpose of desorption. Furthermore, after the completion of the desorption process, filtration
takes place and gives heavy metal ion solution which is kept in a tank for further purification
and the used adsorbent is recycled for re-use.
Igwe and Abia (2006) concluded by ascertaining that previous experimental data gotten from
isotherm calculations, kinetics studies and intra particle studies are useful in calculating
energy balances and material balances, and the plant specifications for the development of an
industrial biosorption plant. However, as stated by Igwe and Abia (2006), more research is
required for the implementation of such technology in industries.
2.8 Conclusion
The literature review highlighted the importance of using agricultural wastes for heavy metal
removal from industrial effluents in Nigeria, moreover various investigations carried out by
researchers showed that rice husk, orange peel, maize cob and sugarcane bagasse are suitable
agro wastes for the sorption of lead from aqueous solution regardless if untreated or treated.
But their rate of absorption and adsorption capacities differs depending on various factors like
adsorbent pre-treatment methods, their surface characteristics, pH of the solution, adsorbent
loading, contact time and temperature.

38
However, as the aim of this study depicts, the best method in terms of using agricultural
wastes need to be identified for easy implementation of the biosorption method in Nigeria.
In order to achieve this aim, absorption capacities of these selected wastes have to be
considered in relation to cost effectiveness, also social and political impacts of implementing
this method in Nigeria have to be studied.
The next chapter discusses the methods used for the critical analysis in identifying the best
agricultural waste that is suitable for Nigeria.

39
CHAPTER 3: Methodology
3.1 Methodology
In this study, extensive secondary data will be sourced and analysed to generate a clear
understanding of the aim and objectives. Figure 3.1 below illustrates the overview of the
research study. From various agricultural wastes used as adsorbents for the biosorption
process, four of them, namely; orange peels, rice husk, sugarcane and maize cob were selected
for the study.
Secondary data will be used to undergo comparison between different parameters involved in
the process of biosorption of lead, such parameters include; adsorption capabilities of the low
cost agricultural wastes, their adsorption rates, modification methods, equilibrium time for the
experiment and the availability of the selected adsorbents in Nigeria. Similarly, various
reports and peer review papers that have discussed the removal of lead using the selected
agricultural wastes at different conditions will be sourced. Furthermore, the comparison will
also involve the use of statistical analysis obtained from secondary sources.
Papers from chemistry journals are sourced to characterize the adsorbent surfaces and to
gather information on their physicochemical properties.
Figure 3.1: Overview of the research study
Biosorption
Process
Sugarcane
bagasse
Rice
husk
Orange
peels
Secondary
data collection
SWOT analysis
PEST analysis
Nigeria
Results
Best method
identification
Agricultural
wastes
Maize
Cobs

40
3.2 Analytical Tools
The tools that will be used to make comparison between the selected agricultural wastes are S-
W-O-T and P-E-S-T analytical tools.
3.2.1 SWOT analysis
Basically SWOT is an acronym for strength, weakness, opportunity and threats, and it is used
as a method for choosing a suitable strategy for embarking on a project by considering the
projects internal capacity (strength and weakness) and its external situation (opportunity and
threats) (Oetomo and Ardini, 2009). However after identifying SWOTs, the strength can be
used as an advantage over weakness and the threats can be converted to opportunities (Miller,
2006).
The SWOT analysis will be aided by the use of a SWOT matrix shown in Table 3.1 below, in
which the strengths, weaknesses, opportunities and threats of each method will be highlighted
upon, and the possible solutions to combat this weaknesses and threats by making use of the
existing opportunities and strengths will be discussed. Further to the discussion, the best
method that is most viable in the Nigerian context will be determined.
Table 3.1: Template of the SWOT matrix
STRENTHS WEAKNESSES
C Strength 1
Strength 2
Strength 3
D Weakness 1
Weakness 2
Weakness 3
OPPORTUNITIES
A Opportunity 1
Opportunity 2
Opportunity 3
E F

41
Box A represents the opportunities involved in making use of the agricultural waste for the
biosorption process, box B contains the threats associated with the usage of the agricultural
waste, box C is the strength of the particular agricultural waste, and box D contains the
weaknesses of the agricultural waste. As part of the analysis, box E contains the processes
initiated to take advantage of the opportunities by making use of the strength possessed by the
agricultural waste, box F represents the processes involved to reduce the adsorbent
weaknesses by making use of the opportunities, box G contains suggestions in which the
strength can be used to anticipate or reduce the threats involved in using the adsorbent, and
box H contains the suggestions for reducing the weaknesses possessed by the adsorbent and
also to reduce the threats of using the adsorbent.
3.2.2 PEST analysis
PEST is an acronym for political, economic, social and technology. It is an analytical tool for
comprehending the political, economic, social and technological aspects of an operation
(CIMA, 2007). It is perceived that the PEST analysis coupled with SWOT analysis will give a
better understanding of the scenario being analysed and will in turn produce a better
judgement.
3.2.3 Justification in using SWOT and PEST analytical tools
These methods of analysis where employed because they are believed to be most applicable
for the caparison between the agricultural wastes for the biosorption process. In addition,
SWOT and PEST analysis best explains thoroughly the strength, weakness, opportunity and
threats involved with the use of the selected agricultural wastes as well as the political,
economic, social and technological views of their application in the Nigerian community.
THREATS
B Threat 1
Threat 2
Threat 3
G H

42
More so, this approach facilitates judgements based on key factors identified by the SWOT
and PEST analysis, and consequentially a critical evaluation of these factors will bring to a
conclusion of identifying the best agricultural waste method that suits industrial effluent
treatment in Nigeria.

43
CHAPTER 4: Results and Discussion
The following parameters are used to identify the data for the SWOT and PEST analysis of
orange peels, sugarcane bagasse, maize cobs and rice husk;
(i) Availability in Nigeria
(ii) Absorption capacities
(iii) Equilibrium time for adsorption
(iv) Adsorption rate
(v) Adsorbent treatment methods
(vi) Desorption rate (Metal recovery)
(vii) Social and environmental impact
4.1 Availability of the selectedagricultural wastes
It is of great importance that the agricultural waste for the biosorption process must be
indigenous to Nigeria and as part of the data collection for the analysis of the different
methods for biosorption in Nigeria, the geographical distribution and availability of these
agricultural wastes are required. Hence, the following sections identifies the agricultural
wastes and there availability in Nigeria;
4.1.1 Availability of Orange peel in Nigeria
Citrus fruits are well grown in Nigeria but the most produced citrus fruit is the sweet orange
which is grown and cultivated in fifteen states of Nigeria. However it has been reported that
about 0.3 million tonnes orange wastes yearly are generated in Nigeria which implies that the
wastes in form of peels will be in high volume and if not in use will constitute environmental
pollution. (Oluremi, et al., 2006, Ezejiofor, et al., 2011). Moreover to make these waste
materials useful, they can be turned into adsorbent for the biosorption process.
Although peels are thought to be a source of food for livestock, but its low nutrient contents
and bitter taste makes its usefulness limited in that aspect (Oluremi et al 2006), and thereby
give room for such a chunk of produced orange waste to be used in processes like biosorption.

44
4.1.2 Availability of Sugarcane bagasse in Nigeria
Sugarcane bagasse is the bit left after the juice of the sugarcane has been sucked out
(Alsharief 2012). Nigeria’s main raw material for sugar production is sugarcane, hence the
availability of bagasse as waste is linked to places with sugar production (Rossi, et al., 2002,
Abgoire, et al., 2002).
4.1.3 Availability of Rice husk in Nigeria
Erenstein et al., (2003) reported that rice is a cash crop produced mainly for commercial
purposes in Nigerian, but due to the fact that rice production yields a low return, there is
reduction in its productivity and consequentially increase in the cost of production.
Furthermore, policies have not been able to procure a place in the market for locally produced
rice merchants, so rice imports in Nigeria have been reported to have a giant share in the
statistics of imported agricultural produce into Nigeria (Erenstein et al., 2003, Nigerian
Tribune, 2010). Since rice is majorly imported in Nigeria, the existence of rice husk is limited
and therefore be a constraint for its use in biosorption process.
4.1.4 Availability of Maize cob in Nigeria
Nigeria is regarded as the second largest producer of maize in Africa, moreover the Nigerian
climatic condition favours maize growth. Cob, a part of the maize that bears the grain
represents 30% of maize agricultural wastes and being that about 8 million tonnes of maize is
produced in Nigeria annually with an increase of 23% in the production prediction between
2010 and 2015, there is an indication that corn cobs are produced in large volumes in Nigeria
(Akinfemi and Ladipo, 2011, Saliu and Sani, 2012, Ogunbode and Apeh, 2012).
4.2 Description of other comparison parameters
To understand the significance of the data acquired from work done by researchers used in
this study, it is paramount to understand the following terms;

45
4.2.1 Adsorption capacity
This is the maximum value of the amount of lead that is adsorbed per gram of the agricultural
waste (adsorbent) at equilibrium time (Knaebel 1995).
4.2.2 Equilibrium time
This is the time at which the concentration of the metal ions being adsorbed by the adsorbent
is equal to the concentration of the exchanged ions leaving the surface of the adsorbent. At
this time, the surface of the adsorbent becomes saturated and cannot accept any more metal
ions (Site, 2000).
4.2.3 Adsorption rate
The percentage ratio of the adsorbed lead concentration to the total concentration of lead
present in the aqueous solution is termed adsorption rate. So therefore, it is the total amount of
lead adsorbed from aqueous solution by the adsorbent (Site, 2000).
4.2.4 Desorption rate
This is the percentage of removing the adsorbed metal ion from the adsorbent by using a
suitable reagent. The efficiency of the desorption process is known by the difference between
the quantity of lead in the desorption solution and the quantity of lead adsorbed by the
adsorbent (Akissi, et al., 2010).
4.3 Data collected
Table 4.1 below shows the data collected from the work done by researchers comprising of
the comparison parameters described above. All experiments by the researchers were done at
room temperature and they all stated that the adsorption capacities were pH dependent, in the
sense that increase in pH increases the adsorption capacities. The optimum pH whereby the
best lead adsorption occurred has been indicated in Table 4.1. However, pH higher than the
optimum values will encourage the precipitation of lead hydroxide which will hinder the rate
of lead adsorption.

46
Table 4.1: Work done by researchers on the removal of lead from aqueous solution using the
Selected agricultural wastes
Agricultural
wastes;
unmodified/
modified.
Modifica-
tion
methods.
Adsorption
capacity
(mg/g).
Adso-
rption
rate
(%).
Equilibrium
time (min).
Desorp-
tion
rate
(%).
Optimum
pH
Sources
Orange peel
113.5
55.52
64.3
73.5
10
500
-
35.9
5.5
5
Feng
and
Guo,
2012
De
Souza et
al., 2012
Modified
orange peel
NaOH-
CaCl2
NaOH-
Citric
acid
209
84.53
99.4
74.9
10
500
-
38.0
5.5
5
Feng
and
Guo,
2012
De
Souza et
al., 2012
Korean
mandarin
orange peel
13.5 44.2 50 5 Park,
2010
Rice husk 0.06216 96.8 60 - Elham,
et al.,

47
2010
Modified rice
Husk
Tartaric
acid
15%
alkali
treatment
with
autoclave
(Biomatri
x)
108
58.1
93
80
120
120-150
-
-
5.3
(5.5˗6) ±
0.1
Wong,
et al.,
2003
Krishna
ni, et al.,
2008
Sugarcane
bagasse
6.366 100 120 5 Martín
Lara, et
al., 2010
Modified
Sugarcane
bagasse
Sulphuric
acid
Citric
acid
Triethylen
e-
tetramine
7.297
52.63
313
100
-
-
120
1440
50
-
98
-
5
-
5
Martín
Lara, et
al., 2010
Dos
Santos,
et al.,
2010
Osvaldo
, et al.,
2007
Maize cob 1.09 - 90 - 5 Jonglertj
unya,
2008
Natural
fungi
growth
14.75
3.150
-
-
90
90
-
-
5
5
Jonglertj
unya,
2008
Nale, et

48
4.4 SWOT and PEST analysis of the selectedagricultural wastes used for lead
biosorption.
As discussed earlier in chapter 3, the SWOT analysis will be aided by a SWOT matrix for a
complete evaluation of each agricultural waste, and to compliment this method of analysis is
the inclusion of PEST analysis.
Table 4.2: SWOT matrix for orange peel adsorbent used for lead biosorption
STRENGHTS WEAKNESSES
C •Unmodified orange peel has
high adsorption capacities of 113.5
mg/g and 55.2 mg/g according to
research by Feng and Guo, (2012)
and De Souza et al., (2012)
respectively.
•Adsorption rate is also high for
unmodified orange peel.
•Equilibrium time for maximum
adsorption is 10 minutes according to
Feng and Guo, (2012) and this is low
compared to other waste adsorbents.
•Modifying with NaOH-CaCl2 gives
adsorption capacity of 209mg/g
which is relatively higher than some
of the adsorbents being compared.
D •Equilibrium time is 500
minutes according to a study by De
Souza et al., (2012), and this is
relatively high compared with the
other agro-wastes.
•The rate of metal recovery is 35.9%
which is quite low as indicated by
the desorption studies carried out by
De Souza et al., 2012.
Modified
maize
Cob
H3PO4
EDTA
144.93 - 60 - 7.5
al.,
2012
Igwe
and
Abia,
2007

49
OPPORTUNITIES A •Orange peel wastes are
in abundance in Nigeria and they
are readily available.
•It can be modified with NaOH-
CaCl2 for better efficiency.
•When implemented with the
biosorption process, it is cheaper
than other conventional processes.
•Policies are available for its
implementation.
E •Being a cheap method for
lead extraction, and because it has a
high adsorption capacity and
absorption rate for lead removal and
coupled with a low equilibrium time
makes it a potential adsorbent for the
biosorption method even when used
untreated.
•Modification with NaOH-CaCl2
gives a better adsorption rate, higher
adsorption capacity and low
equilibrium time.
F •Modifying the orange peel
with sodium hydroxide and citric
acid before the biosorption process,
increases the desorption rate to 38%
which still indicates a low metal
recovery rate.
THREATS
B •Few researchers have carried
out studies on the desorption rate of
lead from orange peel.
•It may require permits or licencing
for implementation and the process
of acquiring them may be tasking or
expensive.
•Modifying the orange peel may
increase the operating cost of the
process.
G •Workshops in the form of
development programs should be
initiated and it will make people
including government officials
perceive the importance of using
orange peel for the biosorption
process. This will reduce any tariff or
licence levy placed on its
implementation.
H •Because few researchers
have studied the desorption rate of
lead from orange peel, other
researchers should utilize the
opportunity by investigating other
avenues for increasing the rate of
the metal recovery from orange
peel.
Table 4.2.1: PEST analysis for orange peel adsorbent used for lead biosorption
POLITICAL
•There are available policies to implement the
biosorption technology using orange peel as an
adsorbent in Nigeria.
ECONOMIC
•It is considered as less expensive and an
economically viable method of lead extraction
from waste water.
•Further treatment is required to dispose the metal
binded adsorbent due to its low desorption rate, and
this increases the operating cost.
SOCIAL
•The method is perceived to be accepted by the
people because it is environmentally friendly.
•Reduces environmental pollution caused by orange
peels.
TECHNOLOGY
•Biosorption is a new technology that is yet to be
implemented at an industrial level.

50
Table 4.3: SWOT matrix for rice husk adsorbent used for lead biosorption
STRENGHTS WEAKNESSES
C •High adsorption rate of
96.8% for unmodified rice
husk.
•Equilibrium time for maximum
adsorption is low for both
modified and unmodified rice
husk.
•Treatment with tartaric acid or
biomatrix formation gives
adsorption capacities of 108mg/g
and 58.1mg/g respectively.
•Adsorption rate is high for both
modification of rice husk.
D •The adsorption capacity is
0.06216 mg/g for unmodified
husk which is the least
compared with the selected agro
wastes.
OPPORTUNITIES
A •It can be modified for better
efficiency by treatment with tartaric
acid, and forming a rice husk bio
matrix also increases its efficiency.
• There are available policies to
implement the biosorption
technology using orange peel as an
adsorbent.
E •It will be a suitable adsorbent
upon treatment with tartaric acid
because its adsorption rate and
capacity will increase.
F •Modifying the rice husk with
tartaric acid will increase its lead
adsorption capacity.
•Available policies indicate
government’s interests in such
environmentally friendly project, so
therefore the government can be
asked to partly fund the project.
This shifts the burden of rice husk
treatment cost away from the
industry.
THREATS
B •Abundance of rice husk waste
materials are not certain because of
reduced rice production in Nigeria
compared with other agricultural
produce.
• Few researchers have carried out
studies on the biosorption of lead
using rice husk.
•If modified with chemical reagents
or heat, it may increase the cost of
the biosorption process compared to
unmodified wastes.
•It may require permits or licencing
for implementation and the process
of acquiring them may be tasking or
expensive.
G •The high adsorption rate or
low equilibrium time may offset
the cost incurred during
modification of the rice husk with
tartaric acid.
H •More investigation is
needed for biosorption of lead using
tartaric acid treated rice husk to
determine the desorption rate.

51
Table 4.3.1: PEST analysis of rice husk adsorbent used for lead biosorption
Table 4.4: SWOT matrix for sugarcane bagasse adsorbent used for lead biosorption
POLITICAL
biosorption technology using rice husk as an adsorbent
in Nigeria.
•Major importation of rice by selected people due to
political motives threatens the abundance of rice husk
required in the biosorption process.
ECONOMIC
•Lead adsorption by rice husk adsorbent requires treatment
of the adsorbent in other to achieve a desirable result.
However, the treatment is done using chemical reagents
and heat. The chemicals contribute additional cost for the
project and the heating will increase the energy
consumption during the process and will in turn increase
the cost.
SOCIAL
• Reduces environmental pollution caused by rice husk.
TECHNOLOGY
• Biosorption is a new technology that is yet to be
•it is perceived to be an easy and straight forward
technology in reducing environmental impact caused by
industrial processes.
STRENTHS WEAKNESSES
C •High rate of adsorption by
untreated bagasse.
•Equilibrium time is low for
untreated bagasse and
triethylene-tetramine modified
bagasse.
•Treatment with citric acid and
triethylene-tetramine increases
its adsorption capacity as
reported by Dos Santos et al.,
(2010) and Osvaldo, et al.,
(2007) respectively.
•Desorption studies by Dos
Santos et al., (2010) confirm the
metal recovery rate to be 98%
which is very high compared to
D •Untreated sugarcane bagasse
gives a low adsorption capacity
for lead.
•Treatment with sulphuric acid
still gives a low adsorption
capacity.
•Equilibrium time is high with the
citric acid treated bagasse.

52
Table 4.4.1: PEST analysis of sugarcane bagasse adsorbent used for lead biosorption
other methods.
OPPORTUNITIES
A •Sugarcane bagasse wastes
are readily available in Nigeria in
millions of tonnes.
•There are available policies to
implement the biosorption technology
using sugarcane bagasse as an
adsorbent.
•It can be modified with triethylene-
tetramine and citric acid for better
efficiency.
E •Potentially, sugarcane
bagasse can be used for
biosorption due to its
abundance, and because there
are available policies requiring
the best available technology for
effluent treatment and its
tendency to be modified with
triethylene-tetramine or citric
acid for better efficiency.
F •The adsorption capacity
is increased upon treatment with
triethylene-tetramine or citric
acid but treatment only with
triethylene-tetramine gives a low
equilibrium time of 50 minutes.
THREATHS
B •If modified with triethylene-
tetramine or citric acid, it may increase
the cost of the biosorption process
compared to unmodified wastes.
•It may require permits or licencing for
implementation and the process of
acquiring them may be tasking or
expensive.
G •The high adsorption capacity
and the high metal recovery rate
for citric acid treated bagasse
may offset the cost incurred
during modification of the
sugarcane bagasse because the
metal recovered can be recycled
and used as raw materials for
other industrial processes and
the adsorbent can also be reused
over again which makes the
process cost effective.
H •Workshops in the
form of development programs
should be initiated and it will
make people including
government officials perceive the
importance of using modified
sugarcane bagasse for the
biosorption process. This will
reduce any tariff or licence levy
placed on its implementation.
•Movement to seek for
government funding will reduce
the cost involved in the adsorbent
treatment method.
•Increasing the low absorption
capacity and reducing the
equilibrium time will be achieved
by modifying the bagasse with
triethylene-tetramine.
POLITICAL
biosorption technology using sugarcane bagasse as an
ECONOMIC
•It is considered as less expensive and an economically
viable method of lead extraction from waste water.

53
Table 4.5: SWOT matrix for maize cob adsorbent used for lead biosorption
STRENTHS WEAKNESSES
C •Low equilibrium time if
unmodified.
•Adsorption capacity of 144.3mg/g
when treated with ethylene diamine
tetra-acetic acid (EDTA).
•A low equilibrium time of 60
minutes when treated with EDTA.
D •Low adsorption capacity if
unmodified.
•Increased adsorption capacity when
treated with natural fungi growth but it
is still low compared to other selected
wastes.
•Low adsorption capacity when
modified with H3PO4.
OPPORTUNITIES
A •There is abundance of
maize cob due to availability of
maize crop in Nigeria.
•It can be modified with a
natural fungal growth, EDTA,
and H3PO4 for better
efficiency.
• There are available policies to
implement the biosorption
technology using maize cob if
considered as the best available
technology (BAT).
E •It should be modified with EDTA
in order to increase its adsorption
capacity, to reduce its equilibrium
time and the abundance of maize crop
makes its cob to be a potential
adsorbent in the biosorption process.
F •From the data obtained, to have
increased adsorption capacity
comparable to other agricultural wastes,
the maize cob has to be treated with
EDTA.
SOCIAL
• Reduces environmental pollution caused by
sugarcane bagasse.
•it is perceived to be a totally acceptable technology
due to its environmental friendliness and cost
effectiveness compared to other conventional
methods of lead extraction.
TECHNOLOGY
•It is perceived to be an easy and straight forward
technology in reducing environmental impact caused by
industrial processes.

54
THREATHS
B •There is no information
on the adsorption and
desorption rate of lead when
using maize cob as the
adsorbent. So therefore there is
limited data on its usage.
•Modifying with natural fungal
growth, EDTA, and H3PO4 may
increase operating cost.
•It may require permits or
licencing for implementation
and the process of acquiring
them may be tasking or
expensive.
G •Further research is necessary to
determine the desorption rate of
EDTA treated maize cob.
•The high adsorption capacity and the
low equilibrium time may offset the
cost incurred during modification of
the maize cob.
H • To reduce the weakness and threats
identified, it is important to treat the
maize cob with EDTA.
•More research is needed to gather
information on the biosorption process
using maize cob as adsorbent.
•Workshops in the form of
development programs should be
initiated and it will make people
including government officials perceive
the importance of using modified maize
cob for the biosorption process. This
will reduce any tariff or licence levy
placed on its implementation.
Table 4.5.1: PEST analysis of maize cob adsorbent used for lead biosorption
4.5 Discussion
4.5.1 Outcome of the SWOT analyses
The SWOT matrix helped in highlighting the main points to consider when using each
individual agricultural waste for the biosorption process. These points are discussed in the
following sections below;
POLITICAL
biosorption technology using sugarcane bagasse as an
ECONOMIC
•It is considered as less expensive and an economically
viable method of lead extraction from waste water.
•Lead adsorption by maize cob adsorbent requires
treatment of the adsorbent in other to achieve a
desirable result. However, the treatment is done using
EDTA and the chemicals may impose additional cost
towards the project.
SOCIAL
•Reduces environmental pollution caused by maize
cob wastes.
•It is perceived to be a totally acceptable technology
due to its environmental friendliness and cost
effectiveness compared to other conventional methods
of lead extraction.
TECHNOLOGY
• It is perceived to be an easy and straight forward
technology in reducing environmental impact caused
by industrial processes.

55
4.5.1.1 Orange peel
Abundance of orange peel in Nigeria suggests the potentiality of it to be a good adsorbent for
the biosorption of lead. However, the SWOT matrix pin pointed out the factors that made
orange peel to be potentially viable for the biosorption process and ironically also shows the
limitation to be encountered if it is implemented in the biosorption process.
For instance, lead adsorption with orange peel was studied by Feng and Guo, (2012) and De
Souza et al., (2012) and they had its adsorption capacities to be of 113.5 mg/g and 55.2 mg/g.
These are good values because they simply depict the amount in grams of lead adsorbed by 1
gram of orange peels and having the values of 113.5 and 55.2mg/g shows that a substantial
amount of lead is adsorbed by orange peel. However, not just the adsorption capacity is to be
considered for viability because equilibrium time for the reaction is also an important factor to
consider in the sense that a low equilibrium time shows that the reaction goes at a faster rate
and saves time spent on waste water treatment.
The equilibrium time of 10 minutes determined by Feng and Guo, (2012) shows good
efficiency unlike that determined by De Souza et al., (2012) which is 500 minutes. This
denotes a longer process for the research by De Souza et al., (2012) to achieve a 55.2mg/g
adsorption rate. But the best value obtained for the biosorption process was using NaOH-
CaCl2 treated orange peel which gave 209 mg/g adsorption capacity, 99.4% adsorption rate
and 10 minutes equilibrium time. This favourable values of the comparison parameters for
orange peel doesn’t mean it is better than the other adsorbent because according to a report by
Ngah and Hanafiah (2008), which stated clearly that chemically modified adsorbent may have
high adsorption capacity for metal ions but in other to realise the motive of obtaining a low
cost adsorbent, there has to be caution on the amount spent on modification chemicals and
treatment methods.
Desorption is the recoverability of the metal ion from the adsorbent and this is important for
the re-use of the adsorbent, to recover the metal for use in other manufacturing purposes and
lastly to avoid discarding the adsorbent and the adsorbed metal into the environment because
by doing so, it may generate into a more toxic substance and cause harm to the environment.

56
So very few literature reviews have discussed the desorption rate of lead adsorbed orange peel
except for De Souza et al., (2012) in which the desorption rate was as low as 35.9%.
4.5.1.2 Rice husk
Amongst the few researchers that have carried out research on the use of rice husk adsorbent
for the removal of lead from aqueous solution, Wong, et al., (2003) gave the best result which
shows 108mg/g adsorption capacity, 93% adsorption rate of lead, and 120 minutes of
equilibrium time upon treatment of the rice husk with tartaric acid. There is no known amount
of desorption rate attached to lead binded rice husk. However, rice husk has limitations on its
use as adsorbent because of its availability in Nigeria. For an agricultural waste to be used as
an adsorbent for biosorption, it should be indigenous and readily available in the area where
the biosorption process is being implemented, and the adsorbent should have little or no
economic value.
Rice crop in Nigeria was discovered to be a crop of political importance because there is
inconsistency in the government policies concerning rice crop, this is a bid by the government
to favour some people of high calibre in the society. So this makes the local farmers to switch
to production of other crops and the only way to meet the country’s demand for rice is by
importation (Daramola 2005). Due to this reason, availability of rice husk becomes an aspect
to consider, because if there is a problem with rice importation in the future, obviously
shortage of rice husk occurs and this will hinder the progress of the biosorption technology.
4.5.1.3 Sugarcane bagasse
Like other agro wastes, sugarcane bagasse is readily available in Nigeria because its crop
grows in the wide range of climatic condition present in Nigeria and sugarcane is the major
raw material for sugar production in Nigeria.
Unmodified sugarcane bagasse shows little adsorption capacity for lead from the study
conducted by Martín Lara, et al., (2010), however the best adsorption capacity was achieved
during studies conducted by Osvaldo, et al., (2007) whereby triethylene-tetramine was used to
modify sugarcane bagasse and adsorption capacity of 313mg/g was obtained with equilibrium

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