K0363060080

International Journal of Engineering Science Invention
ISSN (Online): 2319 – 6734, ISSN (Print): 2319 – 6726
www.ijesi.org Volume 3 Issue 6ǁ June 2014 ǁ PP.60-80
www.ijesi.org 60 | Page
Adsorptive Removal of Zinc from Waste Water by Natural
Biosorbents
Sunil Rajoriya1
, Balpreet kaur2
1
(Chemical engineering, 1
Doon Group of Colleges, India)
2
(Chemical engineering, SBSSTC Ferozepur, India)
ABSTRACT: Zinc is a toxic metal and is present in high concentration in wastewater of various industries like
galvanizing, metallurgical, electroplating, mining, paints, pigments, pulp and paper and pharmaceuticals. There
are various conventional treatment techniques available for the removal of zinc from wastewater like chemical
precipitation, ion exchange, reverse osmosis, electro dialysis, electrochemical treatment, membrane separation
process and adsorption. Among these methods, adsorption has been found to be one of most popular process for
the removal of zinc from wastewater due to its low initial cost and sludge free environment.Increasing demand
for eco-friendly techniques promotes the interest to natural and bio-degradable adsorbents. In this work, lemon
peel and banana peel have been used as biosorbents to achieve the desired objective. To study the adsorption of
zinc ions, batch experiments were performed. The characterization of both adsorbents was carried out using
FTIR. The effects of various process parameters like biosorbent concentration, contact time, pH, various initial
zinc concentration and temperature on the removal of zinc from wastewater have been investigated and
optimized. Adsorbent concentration for both biosorbents for the maximum removal of zinc at optimum pH of 4
and temperature of 300
C is found to be 1g/100ml. The optimum contact time for the equilibrium condition is 260
min for the removal of zinc.
KEYWORDS: Adsorption, Batch studies, magnetic stirrer (300
C), Natural Bio-sorbents.
I. INTRODUCTION
1.1 General
Environmental pollution is one of the main problems of the society in the 21st
century. The major
pollutants include toxic metals, the quantity of which permanently increases in the environment as the result of
increased industrial activity. Zinc is one of these toxic metals and is present in high concentration in wastewater
of various industries like galvanizing, metallurgical, electroplating, mining, paints & pigments, pharmaceuticals,
fiber production, ground wood pulp, newsprint paper, batteries, petroleum and petrochemical (Naiya et al.,
2009, King et al., 2008 and Deliyanni et al., 2009). Zinc metal ions do not degrade and thus are carried away to
the food chain and finally get accumulated in the living organisms, causing several diseases and disorders
(Deliyanni et al., 2009). Waste water treatments would not only be economical but will also help to maintain the
quality of the environment. The heavy metals, having hazardous effects on health, can be treated from
wastewater by using various physicochemical methods. The release of large quantities of heavy metals into the
natural environment has resulted in a number of environmental problems.
1.2 Major sources of zinc in waste water
Zinc enters into water through natural as well as anthropogenic sources (anthropogenic effects,
materials or process are those that are derived from human activities as opposed to occurring in natural
environments without human influence). Erosion of soil and rocks has been found to be responsible for natural
zinc contamination in water (Elinder et al., 1986).

Adsorptive Removal Of Zinc From Waste…
Table 1.1 Typical concentration of zinc in waste water of various industries
Table1.2 Typical concentration of heavy metals presents in copper smelter wastewaters (Basha et al.,
2008)
Heavy metal Average zinc concentration (mg/L)
Arsenic 1979
Zinc 300
Copper 164.48
Iron 88
Bismuth 85
Cadmium 76
Nickel 12
Lead 4.6
Chromium 2.3
1.3 Permissible limit and Mechanism of zinc toxicity
The permissible concentration of zinc in drinking water is 5 mg/l, According to US EPA (Naiya et al.,
2009), WHO (Mohan et al., 2002), IS 10500 (Naiya et al., 2009). zinc is initially concentrated in the liver after
ingestion, and is subsequently distributed throughout the body. The liver, pancreas, bone, kidney, and muscle
are the major tissue storage sites.
1.4 Biosorption
Biosorption is an emerging technology that uses biological materials such as dead biomass and living
microbial cells to remove pollutants from solution. Biosorption is a rapid, reversible, economical and in contrast
to physico-chemical methods used for removal of heavy metals from wastewater. Other advantages of
biosorption over physico-chemical techniques include low cost, high efficiency, minimization of chemical or
biological sludge, no additional nutrient requirement, possibility of regeneration of biosorbent and metal
recovery (Norton et al., 2004).
Physico-chemical methods for zinc removal from wastewater
The removal of zinc include coagulation- flocculation, chemical precipitation, membrane filtration,
flotation, ion exchange, reverse osmosis, liquid extraction, activated carbon adsorption and electrochemical
treatment by various physico-chemical techniques (Gupta et. al., 2010).
The above mentioned conventional processes are briefly discussed below:
Available techniques for zinc removal
from water
Figure1.1 Available techniques for zinc removal from water
Industrial wastewater Average concentration (mg/L)
Copper smelter 50-300
Electroplating 9-41
Hot-dip galvanizing 81.86
Rubber thread 81.6
Petrochemical 2.2
Battery 0.18-7.27
Paint 20
Pulp and paper 1.3
Pharmaceutical 0.12
Coagulation-
flocculation
Chemical
precipitation
Flotation Membrane
filtration
Electrochemical
treatment
Activated carbon
adsorption

II. LITERATURE REVIEW
Mohan et al., 2002 investigated the use of low-cost activated carbon derived from bagasse, an
agricultural waste material has as a replacement for the current expensive methods of removing heavy metals
from wastewater. These studies were carried out at the initial concentration of 200 mg/l for Cd+2
and Zn+2.
The
adsorption of Cd+2
and Zn+2
on the prepared adsorbent increases with the increase in pH. The adsorption of Cd+2
and Zn+2
is very low at pH- 2; it increases from 90% to 95% at pH 4.0–6.0. At pH greater than 8.0 the removal
takes place by adsorption as well as precipitation i.e. the OH-
ions from the solution formed some complexes
with Cd+2
and Zn+2
. The removal of Cu+2
, Zn+2
and Ni+2
from solutions using biosorption in cork powder was
described. It was concluded that the adsorption of the heavy metals was favored by an increase in pH (Chubar et
al., 2004). The biosorption of zinc ions from aqueous solution by Tectona grandis L.f. was studied in a batch
adsorption system (Kumar et al., 2006). Nasir et al., 2007 studied that the removal of lead and zinc from
aqueous solutions using chemically modified distillation sludge of rose (Rosa centifolia) petals. Maximum
adsorption of both metal ions was observed at pH 5. Kinetic data was better described by pseudo second order
model rather than pseudo first order kinetic model. The equilibrium studies were carried out at a temperature
300
C. The initial metal ion concentration was taken as 100 mg/l. Adsorption capacity of biomass tends to be in
the order Pb+2
(87.74 mg/g) > Zn+2
(73.8 mg/g) by NaOH pretreated biomass. (Srivastava et al., 2008) studied
that adsorptive removal of cadmium and zinc ions from binary systems using rice husk ash (RHA), The
optimum pH for the removal of Cd+2
and Zn+2
ions by RHA is found to be 6.Biosorption experiments were
carried out at 300
C.
Arshad et al., 2008 utilized the mature leaves and stem bark of the Neem tree for removing zinc from
water. Adsorption was carried out in a batch process with several different concentrations of zinc by varying pH.
The uptake of metal was very fast initially, but gradually slowed down indicating penetration into the interior of
the adsorbent particles. Biosorption experiment was carried out at 250
C. The optimum pH for efficient
biosorption of zinc by Neem leaves and stem bark was 4 and 5, respectively. The maximum adsorption capacity
for zinc is147.08 mg Zn/g for Neem leaves and 137.67 mg Zn/g Neem bark. The obtained results show that pH,
adsorbent particle size, adsorbent dose, initial metal concentration and contact time highly affect the overall
metal uptake capacity of biosorbents. Due to its outstanding zinc uptake capacity, the Neem tree was proved to
be an excellent biomaterial for accumulating zinc from aqueous solutions. Salamatinia et al., 2008 studied that
the sorption of Cu and Zn onto NaOH-treated oil palm frond [OPF] in a fixed-bed up flow column operated in
continuous mode at hydraulic retention times of 6, 12 and 18 mins. The percent removal of 90 % for
Zn+2
adsorption was achieved at optimum pH value. According to Marin et al., 2008, the biosorption of several
metals mainly Cd+2
, Zn+2
and Pb+2
by orange wastes has been investigated in binary systems. Orange waste
consists mainly of cellulose, hemicelluloses, pectin, limonene and many other low molecular weight
compounds. Biosorption experiment was carried out at 250
C. The optimum pH for efficient biosorption of zinc
was 5. Naiya et al., 2009 studied that the various physico-chemical parameters such as pH, initial metal ion
concentration, adsorbent dosage level and equilibrium contact time. The optimum pH for adsorption was found
to be 5 for Zn+2
and the initial metal ion concentration obtained was 25 mg/l. Hawari et al., 2009 studied that the
equilibrium batch dynamics using olive oil mill solid residues as an adsorbent for zinc removal from aqueous
solutions. It was found that the maximum adsorption capacity of zinc was attained at a pH value of 5.0. It was
found that qmax for zinc ions, was 5.63, 6.46, and 7.11mg/g at temperature values of 298, 308, and 328 K,
respectively. At optimum pH a percentage removal of 95 % was achieved. Adsorption experiments were carried
out using waste rice straw of several kinds as a biosorbent to adsorb Cu+2
, Zn+2
, Cd+2
and Hg+2
ions from aqueous
solutions at room temperature. The potential of physic seed hull (PSH), Jantropha curcas L. as an adsorbent for
the removal of Cd+2
and Zn+2
metal ions from aqueous solution has been investigated (Mohammada et al.,
2010). It has been found that the amount of adsorption for both Cd+2
and Zn+2
increased with the increase in
initial metal ions concentration, contact time, temperature, adsorbent dosage and the solution pH (in acidic
range), but decreased with the increase in the particle size of the adsorbent.
III. PRESENT WORK
3. 1 experimental set-up and instrumentation
Removal of zinc was carried out by batch process. In this chapter, analytical and auxiliary instruments
used in the present work have been described.
3.1.1 Batch study
Experiments were conducted with two adsorbents namely banana peel and lemon peel. 100 ml of the
sample volume was taken for each experiment. Batch study was undertaken for the optimization of process
parameters and to extract design parameters like rate constants and isotherm constants.

3.1.2Analytical instruments used in the present study
(i) Atomic Absorption Spectroscopy (AAS)
Used for the determination of Zn (II) in standard and treated solution.
Figure 3.1 AAS, GBC, Avanta, Australia
(ii) Fourier Transform Infrared Spectroscopy (FTIR)
To determine the type of functional groups present on the adsorbents surface before and after adsorption and
thus, to find out the ions responsible for metal adsorption.
Figure 3.2 FTIR, Thermo model AVATR 370 Australia
3.1.3 Auxiliary equipments used in the present study
pH meter, muffle furnace, autoclave, digital camera, weighing balance, oven etc.
3.2 experimental methodology
Banana peel and lemon peel were used as bio-sorbents for the removal of zinc
from waste water. The preparation and characterization of adsorbents, experimental procedure & data recording
for adsorptive removal of zinc from wastewater as well as the bio removal of zinc supplemented with adsorption
are discussed hereunder.
3.2.1 Availability of adsorbents
Lemon peel and Banana peel were used as the low cost natural bio-sorbents. These were sourced from
local market in Dehradun, India.
3.2.2 Preparation of adsorbents
Banana peel and lemon peel were washed with distilled water 3-4 times and Thereafter both these peels
(lemon peel and banana peel) were dried in sun light for 5 days and then in an oven at 900
C for 10 hours. The
adsorbents after drying were used for adsorption studies. They were washed with distilled water several times in
order to remove unreacted citric acid and other soluble substances. The final product was dried in an air oven at

1000
C for 5 hours, later the product was cooled at room temperature in desiccators and stored in air tight
polythene bag. Prepared bio-sorbents are shown in figure below:
Figure 3.4 Prepared bio-sorbents
Figure 3.5 Flow diagram showing various steps of worked carried out

3.2.3 Characterization of the adsorbents prepared
For the characterization of adsorbents, FTIR spectrometer was employed to determine the type of
functional groups present on the adsorbents surface before and after adsorption and thus, to find out the ions
responsible for metal adsorption. Pellets of adsorbent were made with 1 % KBR and 4,000 to 400 cm−1
wavelength was used.
3.2.4 Preparation of zinc metal solution
The stock solution containing 1g/L of standard Zn (II) was prepared by dissolving 2.08 g of AR grade
ZnCl2 in 1000 ml of distilled water. In order to prevent precipitation of metals by hydrolyzing, two drops of HCl
were added to the stock solution. All experimental solutions were prepared by diluting the stock solution with
distilled water.
3.2.5 Batch adsorption studies
Batch adsorption studies were carried out at the desired pH value, contact time and adsorbent dosage
for both the adsorbents. Various initial concentrations of metal solutions were prepared by proper dilution from
stock 1000 mg/L zinc solution standard. pH of the solution was monitored by adding 0.1M HCl and 0.1M
NaOH solution. 100 ml of zinc solution was mixed with calculated amount of adsorbent in a 500 ml conical
flask and the adsorption was carried out in magnetic stirrer at 30°C. After the completion of adsorption, the
sample was filtered and filtrate was analyzed by atomic absorption spectrophotometric method for metal ion
concentration. The amount of metal ion adsorbed per unit mass of the adsorbent was evaluated by using the
same following mass balance equation
qe = ( Co - Ce)
where, qe is the adsorption capacity in mg pollutant/g adsorbent, Co is the initial concentration of pollutant in
solution, Ce is the concentration of the pollutant in solution after equilibrium has been reached, V is the
volume of the solution to which the adsorbent mass is exposed, and M is the mass of the adsorbent.

Figure 3.6 Batch Experiments
3.2.6 Experimental procedure and data recording
3.2.6.1 Procedure on zinc removal at various pH values
Synthetic solution (containing 50 mg/l of zinc) was prepared from stock solution of zinc. Single
Distilled water was used to prepare the solutions. 100 ml of the above stated synthetic solution was taken in
each of the 5 different 100 ml plastic bottles. The pH of this solution was adjusted to 2, 3, 4, 5, and 6 using 0.1M
HCl and 0.1M NaOH solution. For each adsorbent, 5 set of experiments were conducted at different pH 2, 3, 4,
5, and 6 to study the effects of pH on the removal of zinc. 1 g of biosorbent was added to each of these flasks.
Thereafter, these 100 ml plastic bottles were agitated for 6 hr in magnetic stirrer at 300
C. After 360 min of
agitation, the solutions were filtered through filter paper (whatman no.41, 125mm). The filtrate obtained was
diluted using distilled water. The analysis of Zn (II) was done by AAS. The calibration curves for zinc
measurement by AAS have been provided in Appendix (graph-2).
3.2.6.2 Procedure on zinc removal at various adsorbent concentrations
Synthetic solution (containing 50 mg/l of zinc) was prepared from stock solution of zinc. Distilled
water was used to prepare the solutions. The pH of this solution was adjusted to 4.0 using 0.1M HCl and 0.1M
NaOH solution. For each adsorbent, 5 set of experiments were conducted using the adsorbent concentrations of
2.5, 5.0, 10, 20 and 30 g/l to study the effects of adsorbent concentration on the removal of zinc. 100 ml of the
above stated synthetic solution was taken in each of the 5 different 100 ml plastic bottles and was added with
calculated amount of the adsorbent as mentioned above. Thereafter, these 100 ml plastic bottles were agitated
for 6 hr in magnetic stirrer at 300
C. After 360 min of agitation, the solutions were filtered through filter paper
(whatman no.41, 125mm). The filtrate obtained was diluted using distilled water and analysis of Zn (II) was
done by AAS. The calibration curves for zinc measurement by AAS have been provided in Appendix (graph-3).
3.2.6.3 Procedure on zinc removal at various temperatures
For each adsorbent five set of experiments were conducted at different temperature to study the effects
of temperature on the removal of zinc. 100 ml of the Synthetic solution was taken in each of the five different
100 ml plastic bottles and the pH of this solution was adjusted to 4.0 using 0.1M HCl and 0.1M NaOH solution.
1 g of adsorbent was added to each bottle. Experiments were conducted with five bottles at five different
temperatures i.e., 30, 35, 40, 45 and 500
C respectively. After the addition of the adsorbent in the solution in 100
ml plastic bottles (pH adjusted initially), Thereafter, these 100 ml plastic bottles were agitated for 6 hr in
magnetic stirrer at 300
C. After 360 min of agitation, the solutions were filtered through filter paper (whatman
no.41, 125mm). The filtrate obtained was diluted using distilled water and analysis of Zn (II) was done by AAS.
The calibration curves for zinc measurement by AAS have been provided in Appendix (graph-4).
3.2.6.4 Procedure on zinc removal at various contact times
Experiments have been conducted by batch process to study the effect of contact time on the removal of zinc.
100 ml of the zinc synthetic solution was taken in each of the 12 different 100 ml plastic bottles. The pH of this
solution was adjusted to 4.0 using 0.1M HCl and 0.1M NaOH solution. 1 g of adsorbent was added to each
bottle. Thereafter, these 100 ml plastic bottles were agitated for 6 hr in magnetic stirrer at 300
C. After 15 min,
bottle numbered 1 was taken out and the solution was filtered through filter. Similarly after every 15 min bottles
numbered 2-4 were taken out and solution was filtered. Similarly after every 30 min bottles numbered 5-9 were

taken out and solution was filtered. Similarly after every 50 min bottles numbered 10-12 were taken out and
solution was filtered through filter paper (whatman no.41, 125mm). Then the solution was diluted using distilled
water and analysis of Zn (II) was done by AAS. The calibration curves for zinc measurement by AAS have been
provided in Appendix (graph-5).
3.2.6.5 Procedure on zinc removal at various initial zinc concentrations
For each adsorbent four set of experiments were conducted at different initial zinc concentration to
study the effect of initial zinc concentration on the removal of zinc by batch process. 100 ml of the synthetic
solution was taken in each of the four different 100 ml plastic bottles and the pH of this solution was adjusted to
4.0 using 0.1M HCl and 0.1M NaOH solution.
The initial zinc concentration used was 50, 100, 200, and 300 mg/l. After the addition of the adsorbent
in the solution in 100 ml plastic bottles (pH adjusted initially to 4), Thereafter, these 100 ml plastic bottles were
agitated for 6 hr in magnetic stirrer at 300
C. After 360 min of agitation, the solutions were filtered through filter
paper (whatman no.41, 125mm). The filtrate obtained was diluted using distilled water and analysis of Zn (II)
was done by AAS. The calibration curves for zinc measurement by AAS have been provided in Appendix
(graph-6).
IV. RESULTS AND DISCUSSIONS
This Chapter covers the discussion and interpretation of results of the present study. Studies in this
chapter have been divided into two Sections as stated below:
Section 4.1 Characterization of the adsorbents
Section 4.2 Adsorptive removal of zinc from synthetic wastewater
4.1 Characterization of the adsorbents Characterization of the adsorbents is discussed in the subsequent
sections:
4.1.1 FT-IR spectra
FTIR spectra of lemon peel and banana peel before metal ion adsorption are shown in figure 4.1 (a) and
(b) respectively. FTIR study revealed that functional groups like amide, hydroxyl, methyl, and carboxyl
vibrations were present in significant amplitude in both biosorbent samples. Strong vibration peaks in between
3,500-3,000 cm-1
were demarcated as the vibrations of O-H and −N-H functional groups (Zakaria et al., 2009;
Norton et al., 2004). Weaker –CH stretch bands are superimposed onto the side of the broad –OH band at 3,000-
2,800 cm-1
. Vibrations at 2,923.57; 2,921.66; 2,852.93; and 2,851.67 cm-1 in figure 4.1 (a) and (b), respectively,
are caused due to the presence of symmetric or asymmetric CH stretching of aliphatic acids (Yao et al., 2008).
Peaks between 1,800-1,300 cm−1
are caused due to the presence of C=C in aromatic rings and C=H stretching
(Rocha et al., 2009). The peak at approximately 1,020 cm-1
is either due to the C=O stretch of the –OH bend.
Absorbance peaks generated due to weak reflectance in between 1,000-500 cm−1
and 700 cm−1
indicated the
presence of miscellaneous oxides and symmetrical vibrations of Si–O (Das and Guha, 2009; Rocha et al., 2009),
respectively. Figure 4.2 (a) and (b) represent FTIR spectra of metal ion loaded lemon peel and banana peel
respectively.
From FTIR spectra of metal loaded biosorbents it was observed that there was a shift in wave number
of dominant peaks associated with the loaded metal. This shift in the wavelength showed that there was a metal
binding process taking place at the surface of biosorbents. There was a major shift in wave number from 1,446
cm-1
for raw lemon peel to 1,456.07 cm-1
for metal loaded lemon peel. Also some of the metal binding groups
present on the surface of biosorbents get diminished or disappeared after metal loading. Strong vibration peaks
in between 3,500-3,000 cm-1
got diminished after metal loading. Also C–O stretch of the –OH bend in range of
1,400 to 1,020 cm−1
almost disappeared from adsorbed biosorbents. Analysis of the FTIR provides the evidence
that functional groups like carboxyl, hydroxyl, carbonyl and other aromatic vibrations were involved in metal
ion adsorption onto biomass surface.

Figure 4.1 FTIR spectra before metal ion adsorption (a) lemon peel (b) banana peel

Figure 4.2 FTIR spectra after metal ion adsorption for (a) lemon peel (b) banana peel
4.2 Adsorptive removal of zinc from synthetic wastewater
This section consists the observations on the removal of zinc from synthetic wastewater by batch
process using biosorbents. Effects of various process parameters such as adsorbent concentration, agitation time,
pH and temperature on the removal of zinc have been studied to select the process parameters for optimum
removal of zinc in batch reactors. Results on these batch studies are discussed below:

4.2.1 Effect of pH on zinc removal
The effect of pH on percentage removal of zinc by lemon and banana peel is shown in figure4.4 (a),
(b). It is shown from figure 4.4 (a) that the percentage removal of Zn (II) increases slowly with increasing pH
from 2 to 4, and thereafter drops slowly. The maximum percentage removal of zinc by lemon peel and banana
peel was 87.5 % and 90.5 % respectively. The optimum pH value for adsorption of Zn (II) by both lemon peel
and banana peel was found to be 4.0. At lower pH, there is net positive charge on the biomass cells, which
results in higher electrostatic repulsion between the metal ions and the H+
ion during the uptake of metal ion
(Naiya et al., 2009). Whereas at higher pH, there is net negative charge on the biomass, which results in
decrease in the electrostatic repulsion and thus increases the biosorption. Similar trend was reported for the
biosorption of Zn (II) on Neem biomass (Arshad et al., 2008) when the extent of biosorption increased from 0 to
86.48% in pH range of 1.0-6.0. According to the results of this initial experiment, all the following experiments
on adsorption of Zn (II) from aqueous solution were carried out by maintaining the solution pH 4.0 for both
lemon peel and banana peel. Zinc metal uptake for L-peel and B-peel were 4.375 and 4.55 mg/g at pH 4
respectively.
Figure 4.4 Effect of pH on removal of zinc (a) Effect on percentage removal
(b) Effect on zinc uptake

4.2.2 Effect of adsorbent dosage on zinc removal
The effect of adsorbent dosage on percentage removal and specific uptake of zinc from aqueous
solution are shown in Figure 4.5 (a) and (b), respectively. It is evident from Figure 4.5 (a) that initially the
percentage removal of zinc increased rapidly with an increase in adsorbent dosage, but after certain adsorbent
dosage the removal efficiency did not increase. Increasing the adsorbent dosage increases the available binding
sites. Thus more surface area is available for adsorption, thereby increasing the zinc percentage removal from
the solution (Hawari et al., 2009). Figure 4.5 (b) shows that the specific uptake decreased with increasing
adsorbent dosage. This is due to the interference between the binding sites and insufficiency of metal ions in the
solution with respect to the available binding sites (Hawari et al., 2009). This can also be explained on the basis
of the definition of specific uptake (q) as given in equation:
q = (Co .V.P)/M (Hawari et al., 2009)
Where C0 is the initial metal concentration in mg/L and P is the percentage removal of zinc; V is the volume of
the solution in liter; and M is the mass of the sorbent used in gm.
Maximum percentage removal of Zn (II) was found to be 83.5 % and 90.50 % respectively for both lemon peel
and banana peel adsorbent at an adsorbent dosage of 10 g/L. Similarly, the specific uptakes for adsorption of
zinc were 4.175 and 4.525 mg/g respectively for both lemon peel and banana peel adsorbent at an adsorbent
dosage of 10 g/L. Similar trend was reported for the biosorption of zinc by sugar beet pulp (Pehlivan et al.,
2006). It was concluded that with increase in sugar beet pulp dose from 0.1 to 1.0 g, the percentage removal
increased from 60 to 70%.
Figure 4.5 Effect of adsorbent dosage on removal of zinc (a) Effect on percentage removal
(b) Effect on zinc uptake

4.2.3 Effect of temperature on zinc removal
With the increase in temperature percentage removal of zinc decreased. For lemon peel Figure 4.6 (a)
and (b), zinc removal decreases from 82.68 % to 71.76 % due to the increase in temperature from 30 to 500
C for
initial zinc concentration of 50 mg/l. For banana peel Figure 4.6 (a) and (b), zinc removal decreases from 86.8 %
to 76.4 % due to the increase in temperature from 30 to 500
C for initial zinc concentration of 50 mg/l. The
percentage removal is decreased with increase of temperature, so it was concluded that the adsorption reactions
are exothermic. Biosorption capacity also increased with decrease in temperature. The decrease of biosorption
capacity at higher temperature may be due to the damage of active binding sites in the biomass.
Figure 4.6 Effect of temperature on removal of zinc (a) Effect on
Percentage removal (b) Effect on zinc uptake
4.2.4 Effect of contact time on zinc removal
The effect of contact time on batch adsorption of 50 mg/L Zn (II) at 300
C and at pH 4.0 by banana peel
and lemon peel is shown in figure 4.7 (a) and (b) respectively. During the experiment contact time was varied
from 0 to 360 min. The results showed that the percentage removal of metal ion by both the adsorbents
increased by increasing contact time. The rate of increase in the percentage removal of zinc with increase in
contact time is appreciably fast at the initial stage. At the beginning of the experiment the number of available

active sites of adsorbents as well as the concentration of zinc in the solution is maximum. Thus, the driving
force for adsorption of zinc on the adsorbent surface is maximum. Further, agitation provides the energy
required to bring the zinc from the bulk of the solution to the active sites of the adsorbent by reducing the
resistance to mass transfer between bulk phase and adsorbent. In fact, all the above three effects promote
adsorption. Hence, at the initial stage, percentage removal of zinc increases very fast with the increase in
agitation period. Time needed to reach equilibrium for adsorption of zinc from aqueous solution was 260 min
both for banana peel and lemon peel adsorbents.
Figure 4.7 Effect of contact time on removal of zinc (a) Effect on percentage
removal (b) Effect on zinc uptake
4.2.5 Effect of initial zinc concentration on zinc removal
The effect of initial Zn (II) concentration on percentage removal and specific uptake by both adsorbents
are shown in Figure 4.8 (a) and (b), respectively. Percentage removal of Zn (II) from aqueous solution decreased
as concentration increased from 50 to 300 mg/L at constant pH. With increase in the concentration, the
percentage removal of the metal ion from solution decreases because at higher concentration, metal ions diffuse
to the adsorbent surface by intraparticle diffusion and the hydrolyzed ions diffuse at a slower rate, thus
decreasing the percentage removal (Arshad et al., 2008). Also at higher metal ion concentration to adsorbent
ratio, higher energy sites get saturated and adsorption starts on lower energy sites, resulting in lower percentage

removal of metal ions (Bhattacharya et al., 2006). Figure 4.8 (b) indicates that the adsorption capacity increased
with increase in initial Zn (II) concentration. Similar trend was reported for the biosorption of Zn (II) on T.
grandis L.f. leaves biomass (Kumar et al., 2006), when, with increase in the Zn (II) concentration, zinc uptake
increased from 4.3868–12.9702
mg /g and the percentage removal of zinc decreased from 73.11% to 43.23%.
Figure 4.8 Effect of initial metal ion concentration on removal of zinc (a) Effect on percentage removal (b)
Effect on zinc uptake
V. CONCLUSIONS
In general, the present study shows that lemon peel and banana peel are effective biosorbents for
removal of zinc ions from water under suitable experimental conditions. Specifically, the following conclusions
can be drawn from the results of this study:
 Zinc adsorption on these biosorbents is highly dependent upon solution pH. The optimum pH for lemon
peel and banana peel is found to be 4 with removal efficiencies of 87.5% and 90.5% respectively.
 The maximum removal of zinc occurs at an adsorbent dosage of 1g/100ml for both the biosorbents, so this
can be considered as an optimum dosage under specific conditions.

 The percentage removal of zinc and adsorption capacity was found to decrease with increasing temperature,
indicating the exothermic nature of the process.
 The optimum contact time is found to be 260 min for lemon peel and banana peel.
 With an increase in initial Zn (II) ion concentration, adsorption capacity of Zn (II) ions by
both biosorbents is found to increase and the % removal of Zn (II) ions is found to decrease.
VI. SCOPE OF FURTHER WORK
Based on the results of the present study, the following recommendations are suggested for further
investigations.
 The results of this study can also be used in designing column reactor for removal of
Zinc from water.
 Study can also be performed on industrial waste water of various other industries like paints and pigments,
battery, ground wood pulp production, pulp and paper industries etc.
 Thermodynamics study can be performed by using both adsorbents (lemon peel and banana peel) for further
investigation.
VII. ACKNOWLEDGEMENTS
I would like to express the deepest gratitude to my project advisor and mentor Mrs. Balpreet Kaur for
her supervision, advice, and guidance from the very early stage of this thesis work. She continually and
convincingly conveyed a spirit of adventure regard to research. She provided me unflinching encouragement
and support in various ways. Without her guidance and persistent help, this dissertation would not have been
possible.
I am highly grateful to Associate Professor Dr. Rajeev Kumar Garg, Head, Department of Chemical
Engineering, (SBSSTC Ferozepur) for providing necessary facilities and encouragement during the course of
the work. I express my sincere thanks to all faculty members of the Department of Chemical Engineering
SBSSTC, Ferozepur, for their help during the course of work.
I am thankful to Dr. Neelkanth Grover, Associate Professor, Head, Department of Mechanical Engineering,
(SBSSTC Ferozepur) for his invaluable help and encouragement throughout my post graduation.
I am heartily thankful to all Faculty Member, Department of Chemical Engineering, Doon College of
Engineering and Technology, Dehradun, who helped me time to time regarding my project.
I must record my heartfelt appreciation for my wife, Mrs. Garima Rajoriya, who never complained and kept
my spirits high. She not only managed the kid’s studies and family problems but also spared me with a pleasing
smile from most homely chores to accomplish this project. My heart also owes out naturally in appreciation of
my caring daughter Saumya who never complained even if she felt lack of attention from me on account of this
project. Above all, I render my gratitude to the Almighty who bestowed self confidence, ability, strength and
path for accomplishing this work.
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APPENDIX
Calibration curve are shown as below:
Graph -1 Calibration curve of std. zinc (II)

Graph -2 Calibration curve of Effect of pH (a) lemon peel (b) banana peel

Graph -3 Calibration curve of Effect of adsorbent dosage (a) lemon peel (b) banana peel
Graph -4 Calibration curve of Effect of temperature (a) lemon peel (b) banana peel

Graph -5 Calibration curve of Effect of contact time (a) lemon peel (b) banana peel

Graph -6 Calibration curve of Effect of Initial concentration (a) lemon peel
(b) banana peel

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