This is the Text of a Technical Presentation by Prof. Samson O. Ojoawo, FNICE at the May 2023 Monthly meeting of the OSUN STATE CHAPTER, NIGERIAN INSTITUTION OF CIVIL ENGINEERS (NICE) delivered on Saturday May 20, 2023

1. WASTE TO WEALTH:
DEVELOPING AGROWASTE ADSORBENTS IN
REMEDIATING HEAVY METALS FROM
INDUSTRIAL WASTEWATER
A TECHNICAL PAPER
DELIVERED BY
Samson Olakunle OJOAWO, MNSE, FNICE, COREN Regd., Ph.D
Professor of Civil Engineering, Ladoke Akintola University of
Technology Ogbomoso
@
TECHNICAL PRESENTATION @ THE NIGERIAN INSTITUTION OF
ENVIRONMENTAL ENGINEERS, OSUN STATE CHAPTER’S
MONTHLY MEETING
Saturday 20th May, 2023

2. Presentation Outline
• The general challenge and the way out
• Model 01- Preparation and
characterisation of Carica papaya Stem
Activated Carbon (CSAC) adsorbent
• Model 02- Development of Azardirachta
indica Bark Activated Carbon (ABAC)
adsorbent
• Conclusion and Recommendation
• References
ADDRESSING INCESSANT FLOODING,
EROSION AND ECOLOGICAL CHALLENGES
IN NIGERIA' KEYNOTE PAPER BY PROF.
2

3. THE GENERAL CHALLENGE AND THE WAY OUT
3
❑Biosorption becomes popular
due to:
✓Effectiveness & low cost,
✓Renewability & regeneration
✓Ecosystem intimacy
✓Waste conversion to wealth
✓Resource recovery

4. Model 01
PREPARATION AND
CHARACTERIZATION OF
CARICA PAPAYA STEM ACTIVATED
CARBON (CSAC) ADSORBENT

5. OBJECTIVES
5
❑ To produce and modify activated carbons from
Carica papaya stem and Azardirachta indica Bark.
❑ To investigate the operational parameters
(adsorbent dosage, agitation rate, contact time,
particle size, pH and temperature) using batch
method for the selected Toxic metals (TMs) ions in
MW using the prepared adsorbent.
❑ To determine the efficiency of Carica papaya stem
activated carbon (CPSAC) and Azardirachta indica
Bark Activated Carbon (ABAC) in the remediation of
the selected toxic metals from the mining
wastewater.

6. Collection and Processing of Agrowastes
Development of Adsorbents
Investigation of Effects of Selected Adsorption factors
through One Factor At a Time (OFAT)
6
RESEARCH METHODOLOGY

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❑CPS - Collected from LAUTECH Teaching & Research farm
✓Processed into powdery form
❑ Mining Wastewater – collected from Igbeti
✓ Digested and Filtered
✓ Atomic Absorption Spectrophotometer (AAS) readings of
heavy metals’ concentration

8. DEVELOPMENT OF ADSORBENTS
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✓Activating Agents –H3PO4 and NaOH

9. INVESTIGATION OF EFFECTS OF SELECTED ADSORPTION FACTORS (Cont’d)
9
✓One factor At a Time (OFAT) analyses were carried out
for all the adsorption factors
✓The Removal Efficiency (RE) of the Toxic Metals (TM)
removed established
✓The two different CPSACs and MW were used

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RESULTS
➢The Activation resulted in CPSACs with
large surface area (i.e. opening of surface
area) and porous surface (increase in
porosity) structure, which provided good
surfaces for the heavy metals to be trapped
and adsorbed.

11. TABLE 1: TOXIC METALS’ CONCENTRATIONS PRESENT IN THE MW
11
Toxic Metal
Concentration (ppm)
B4
Treatment After Treatment WHO
(2011)
Standar
ds
Mining
Wastewater
CPSAC
- NaOH
CPSAC –
H3PO4
Cobalt 9.60 ± 0.05 ND ND -
Iron 756.50 ± 0.1 ND ND 0.3
Lead 45.80 ± 0.06 ND ND 0.01
➢The harmful metal concentrations were all higher above the WHO
(2011) requirements
➢All Heavy metals were totally eliminated after treatment with optimal
CPSAC – NaOH and H3PO4 concentrations

12. Model 02
Development of
Azardirachta Indica Bark
Activated Carbon
(ABAC) adsorbent

13. ABAC Adsorbеnt matеrial and
prеparation
• The Azadirachta indica bark for the study was
acquirеd locally from Ladoke Akintola University
of Technology (LAUTECH) Teaching and
Research Farm, Ogbomoso, Nigеria.
• It was cut into pieces,
• thoroughly washеd with distillеd watеr to removе
all possiblе impuritiеs and contaminants,
• oven dried at 105C and ground into powder.
• The adsorbent was prepared using HCl and NaOH
as activating agents in accordance with modified
methods from Bello et al., 2015 and Ojoawo et al.
(2016).

14. Graphical abstract on preparation of
Azardirachta Indica Bark Activated Carbon

15. Phytochemical analysis:
• Confirmatory phytochemical qualitative
tests on the Azadirachta indica bark
powder were conducted according to
Yadav & Agarwala (2011), ULM (2017)
standard methods.
• The tests were carried out at the
agronomy laboratory of the University of
Osun,
• Ejigbo Campus, Nigeria.
• The tests were conducted for 5 functional

16. • Alkaloids were measured by dissolving 0.5 g of
Azadirachta indica bark powder in 96% ethanol
and 20% NaOH (1:1)
• 1 ml of the filtrate was added to 5 ml of 60%
NaOH and allowed to stand for 5 min.
• 5 ml of 0.5% formaldehyde was added and
allowed to stand for 3 hours.
• Flavonoids were measured by the hydrolysis of
spectrophotometric method.
• 0.5 g of processed Azadirachta indica bark
powder was mixed with 5 ml of dilute H3PO4 and

17. • The boiled extract was allowed to cool and was
then filtered
• 1 ml of the filtrate was added to 5 ml of ethyl
acetate and 5 ml of 1% NH. This was then
scanned from 420 to 520 nm for the absorbance.
• Phenols and tannins were determined by mixing
5 ml of extract with 2 ml of 2% solution of H3PO4
• a blue-green or black colour showed the
presence of phenols and tannins.
• A mixture of 5 ml of extract and 5 ml of distilled
water in a test tube that was shaken vigorously
indicated the presence of saponins by the
formation of stable foam.

18. (ii) Proximate analysis:
• Conducted at Agronomy laboratory of
University of Osun, Ejigbo Campus, Nigeria
according to AOAC (1990) and ULM (2017)
standard methods.
• The test was conducted for Ash,
Carbohydrates, Crude fibre, Proteins
and Moisture contents of the
Azadirachta indica bark powder. The
Ash and Moisture contents were
determined using weight difference
method.
• Crude fat were extracted by means of

19. • Crude fiber was extracted by successive
digestion of the defatted samples
• with 1.25% Sulphuric acid and 1.25%
Sodium hydroxide solutions. The Nitrogen
value, which is the
• precursor for Protein of the powder was
determined using digestions, distillation
and titration of the sample.
• The Nitrogen value was converted to
protein by multiplying with a factor of
6.25, while Carbohydrate was determined
by difference method.

20. Conclusion & Recommendation
❑ Activation plays prominent roles in
enhancing the functional groups and
well development of pores on the
adsorbents.
❑ Increased agitation rate, temperature
and contact time largely influenced the
treatments.
❑ All Heavy metals (Co2+, Fe2+ and Pb2+)
were totally eliminated after treatment
20

21. ❑ The Azadirachta indica bark Activated Carbon
(ABAC) is an efficient adsorbent capable of
remediating Cu2+ Zn2+, Cd2+, Cr3+, Co3+ and
Pb wastewater.
❑ It has presence of some functional groups and
metabolites, which resulted in heavy metals
binding ability and myco-toxicity influence.
❑ ABAC using HCl has optimum agitation rate,
contact time, grain size, pH and temperature
values of 150 rpm, 120 minutes, 2 mm, 7 and
30°C respectively.
❑CPSAC and ABAC are perfect examples of
agrowastes turned to wealth.

22. References
• Adetoro, A.E and Ojoawo, S.O (2020) Optimization Study of
Biosorption of Heavy Metals from Mining Wastewater using
Azadirachta Indica Bark Adsorbents. Water Science and
Technology, 82 (5): 887 - 904. DOI: 10.2166/wst.2020.394.
• AOAC. 1990. Official Methods of Analysis 15th ed, Association
of Official Analytical Chemists (AOAC), Washington D. C., US,
pp. 602 - 612.
• Adetoro, A.E and Ojoawo, S.O. (2021) Optimization study on the
biosorption of toxic metals from mining wastewater using
Carica Papaya Stem activated carbon. Proceedings of the
International Conference on Civil Engineering Trends and
challenges for sustainability, (CTCS-2021, Virtual), Nitte, India,
NMAM Institute of Technology, of the Visvesvaraya
Technological University, Belgaum, India, 2021. 22

23. • Bello, O. S., Adegoke, K. A. & Akinyunni,
O. O. (2015) Preparation and
characterization of a novel adsorbent
from Moringa oleifera leaf. Applied Water
Science. doi:10.1007/s13201-0150345-4.
• Ojoawo, S. O., Udayakumar, G., Adewale,
A. A. & Ogunowo, A. T. (2016) Adsorption
potentials of carica papaya in remediating
Pb4+ and Cr3+ from metal – galvanizing
industrial wastewater. International
Journal of Innovative Trends in
Engineering (IJITE) 21 (01), 52–61.
• UNIOSUN Laboratory Manual – ULM,
(2017) Laboratory Manual for Students.
College of Agriculture, University of Osun,

24. • Yadav R.N.S., & Agarwala M. (2011)
Phytochemical analysis of some
medicinal plants, centre for studies in
Biotechnology. Journal of Phytology, 3,
10-14.
• World Health Organization (2011) WHO,
“Guidelines for Drinking-Water Quality.
Switzerland, Geneva, pp. 1 – 564, 2011.

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THE END