The document summarizes research investigating the potential use of the filamentous green algae Oedogonium sp. for removing trace elements like copper, cobalt, chromium, iron, mercury, nickel, zinc and uranium from aqueous systems in gold mining sites. Through a series of batch experiments, the researchers found that Oedogonium sp. effectively adsorbed these metals from multi-ion solutions with maximum adsorption capacities comparable to literature values. The adsorption was influenced by factors like pH, concentration, contact time and temperature. Over multiple cycles of adsorption and desorption, the algal biomass could be regenerated and reused, increasing its adsorption efficiency. The study highlights the potential of this algal biomass

1. BIOSORPTION OF TRACE ELEMENTS FROM AQUEOUS SYSTEMS
IN GOLD MINING SITES BY THE FILAMENTOUS GREEN
ALGAE (Oedogonium sp.)
E.N. Bakatula1, E.M. Cukrowska1, I.M. Weiersbye2 & H. Tutu1
1School of Chemistry, 2School of Animal, Plant and Environmental Sciences
University of the Witwatersrand, Johannesburg
July 2013

2. Introduction
Objectives
Experimental work
Results and discussion
Conclusion
Presentation outline

3. They must be removed from the
polluted streams in order to meet
increasingly stringent environmental
quality standards.
Heavy metals
Special concern
Non-
biodegradable
Toxicity
Bioaccumulation
Persistent
Budget up as travelling food chain
– serious threat to humans and
animals
The entire environment
is at stake
Introduction
Effluents generated by the mining activities in South Africa result in several
environmental challenges, among which water pollution has been the most significant.
They contain large quantities of toxic substances, such as cyanides and heavy metals,
which have serious implications on human health and ecologically.

4. Several methods have been proposed to remediate mine wastewaters but most of them
are either inefficient or very expensive and also have drawbacks.
Physico-chemical
remediation
Phytoremediation =
Green remediation
 Coagulation – flocculation
 Reverse osmosis; Flotation
 Ultra-filtration; Ion exchange;
 Precipitation ; Electro-dialysis
 Activated carbon adsorption
Use of plants to partially or substantially
remediate selected substances in
contaminated soil, sludge, sediment,
groundwater, surface water and wastewater.
(Pivetz, 2001).
Introduction cont....
Micro-organisms are stimulated to degrade
hazardous organic and inorganic
contaminants to environmentally safe levels
in soils, subsurface materials, water, sludge,
and residues.
Bioremediation

5. Biosorptive properties of green algae: Oedogonium sp.
Oedogonium is an unbranched, filamentous
green algae with distinctive rings at the apical
ends of certain cells.
Biosorption in algae has mainly been attributed to
the cell wall properties where both electrostatic
attraction and complexation can play a role. The
cell wall consists of:
- polysaccharides – cellulose, fucoidan, fucose,
alginic acids or alginate.........
Alginic acid
-proteins (chitin) and phosphate carbohydrates
and hence offers a number of active sites
capable to bind metal ions, they may act
individually or in synergy.
Biosorption is a passive metabolic process, reversible and occurs at a faster
rate.

6. The complex structure of the algae implies many ways
for the metal to be taken up. The biosorption
mechanisms are various and not fully understood.
They may be classified according to various criteria;
depending on the location.
Mechanism of the biosorption
Advantages of the biosorption
 Low cost
 High efficiency
 Minimisation of chemical and biological
sludge Ecofriendly nature
 Used both in situ and ex-situ
High efficiency in dilute effluents
 Regeneration of biosorbent
Possibility of metal recovery

7. Objectives
This research investigated the potential use of the filamentous green algae
(Oedogonium sp.) for the removal of Cu, Co, Cr, Fe, Hg, Ni, Zn and U in multi-ion
system from mines wastewater.
To assess the effects of contact time, pH, concentration and temperature on the
adsorption capacity.
To investigate the regeneration of such materials for a potential re-use and recovery of
some valuable metals.

8. EXPERIMENTAL WORK
The algal strains were collected from a dam
wastewater bodies receiving gold mining effluent.
Metal analysis of the dam water as well as the metal concentration at
equilibrium was done using the ICP-OES.
3. Batch adsorption studies of Cu, Co, Cr, Hg, Fe, Ni, Zn and U in multi-ion system
onto algal biomass
a. Effect of pH (2 – 7)
b. Effect of initial metal concentration (50 - 500 mg/L) – Adsorption
isotherms
c. Effect of contact time (10 – 180 min) – Kinetic study
d. Effect of temperature (20 and 40oC) – Thermodynamic parameters
4. Desorption of metals adsorbed ( 0.1 M HCl) and re-use of the biomass
2. Characterisation of the algal biomass
- FT-IR
- CHNS
1. Preparation of algal biomass
- Washing with D-H2O Freeze dried

9. RESULTS AND DISCUSSION
1. Characteristic of the biomass
 Elemental composition
(CHNS)
C:24.9%
N: 4.12%
S: 5.85%
 FT-IR Spectra
OH;
NH
COOH; NH;
CO; PO4
-3
C-C; -
CN
OH
CH
• The algal sample had functional groups, namely: carboxylic acids, amines,
alkanes, alcohols, ethers.
• The class of compounds present in the algae are therefore:
carbohydrates, organic acids, proteins, polysaccharides.....

10. Water bodies from the dam was polluted with the following:
Results and discussion, cont.....
2. Metals analysis
EC – 2.372 mЅ.cm-1
pH – 8.57Metal mg/L Metal mg/L Metal mg/L
Ag 0.075 Co 1.6 Mg 38
Al 3 Cr 0.2 Mn 196
As 0.04 Cu 0.15 Ni 1.25
Au 0.98 Fe 22.5 Zn 2.5
Pb 0.07 U 0.045
The results point to pollution of the dam by toxic elements, with concentrations
higher than the regulated limit by the Department of Water Affairs (SAWQ, 1996).
Co 0-50 μg/L; Cr 0-20 μg/L; Cu 0-200 μg/L; Ni 0-200 μg/L; Zn 0-1000 μg/L; U 0-0.4 μg/L
Fe 0-500 μg/L (SAWQ).

11. 35
40
45
50
55
2 3 4 5 6 7 8
qe(mgg-1)
pH
Cu
Ni
Zn
Co
35
40
45
50
55
2 3 4 5 6 7 8
qe(mgg-1)
pH
Fe
Hg
U
Cr
Effect of pH on the biosorption of Cu, Co, Cr, Fe, Hg, Ni, Zn and U for Oedogonium sp. in a multi-component
solution (Ci = 100 mg L-1, pH = 3, algal mass = 1g, Temp = 25 oC)
Uranium species in
aqueous solution
3. Adsorption studies
Effect of pH

12. Parameters of the Langmuir, Freundlich and D-R models for the adsorption of
metals onto oedogonium sp. biomass in multi–ion system
 Effect of initial metal concentration – Biosorption isotherms
The adsorption of Cu, Co, Cr, Hg, Ni and Zn fitted the freundlich as well
as the D-R isotherms – bound on heterogeneous surface with ion
exchange being the main process.
Fe and U are not described by any of the cited models.
Metal Langmuir constant Freundlich constant Dubinin-Radushkevich
constant
b
(L/mg)
qm
(mg/kg)
R2 n KF
(mg/g)
R2 Xm
(mol/kg)
Es
(kJ/mol)
R2
Cu 56.72 0.409 0.909 3.866 1.133 0.965 1.014 10.62 0.961
Co 19.94 0.391 0.894 3.108 1.131 0.996 1.066 8.577 0.992
Cr 45.05 0.681 0.999 4.118 1.155 0.998 1.183 10.18 1.000
Fe 56.64 0.142 0.310 3.929 0.924 0.321 0.815 10.17 0.352
Hg 562.3 0.188 0.996 3.347 1.110 0.993 1.088 10.62 0.997
Ni 16.98 0.446 0.577 3.055 1.141 0.991 1.124 8.323 0.989
Zn 66.89 0.559 0.439 3.969 1.134 0.956 1.153 10.28 0.954
U 383.5 0.091 0.594 2.907 1.083 0.912 1.084 9.428 0.906

13. Effect of contact time – Kinetic study
Effect of contact time on the biosorption of Cu, Co, Cr, Fe, Hg, Ni, Zn and U for Oedogonium sp. in multi-
component solutions (Ci = 100 mg L-1, pH = 3, algal mass = 25 g, Temp = 25oC)
The maximum adsorption was reached after 30 minutes.
The biosorption process followed the pseudo-second-order kinetic with R2 > 0.980
for all the metals studied.
0
10
20
30
40
50
0 50 100 150 200
qe(mg/g)
Time (min)
Cu
Ni
Zn
Co
0
10
20
30
40
50
0 50 100 150 200
Time (min)
qe(mg/g)
Fe
Hg
U
Cr
Kinetic Equilibrium
It appeared that the biosorption of Ni was controlled by the film diffusion process
with the coefficient value of 10-7 cm2/s (Df = 0.23 r0 δ qe / t½ , according to Michelson,
Df = 10-6 - 10-8 cm2/s).

14. The biosorption of metal-ions in a multi-ion system decreases with an
increase in temperature. The process was spontaneous and exothermic.
Effect of temperature – Thermodynamic parameters
qe ∆ H ∆ G
mg g
-1
kJ mol-1 kJ mol-1
293.15 K 313.15 K
293.15 K 313.15 K
Cu 46.7 44.9 -5.535 -2.38 -2.476
Ni 45.4 42.7 -8.634 -2.449 -2.598
Zn 47.2 47.2 -0.598 -2.364 -2.354
Co 46.6 46.4 -0.605 -2.396 -2.385
Fe 43.3 42.8 -1.635 -2.564 -2.593
Hg 49.93 49.41 -1.494 -2.243 -2.217
U 45.7 45.3 -1.238 -2.433 -2.454
Cr 46.3 45.2 -3.386 -2.401 -2.46
qe = amount adsorbed; ∆ H = Enthalpy change; ∆G = Gibb’s free energy

15. 4. Regeneration and re-use of the algal biomass
0
20
40
60
80
100
120
Cu Ni Zn Co Fe Hg U Cr
Sorption%
Adsorption Desorption
 More than 110% of the
metals adsorbed were eluted
from the biomass. These
results indicate that there were
metals initially adsorbed on
the biomass which were also
released during desorption.
 This virtually increases
the adsorption efficiency of
the Oedogonium sp. during
the repeated adsorption-
desorption operations.
Cycle: adsorption-desorption
0
10
20
30
40
50
60
Cu Ni Zn Co Fe Hg U Cr
Adsorptioncapacity(mg/g)
Cycle 1 Cycle 2 Cycle 3

16. Conclusion and future work
• The algal biomass grows naturally in the vicinity of the tailings facilities and
water systems, making it possible and cost-effective to be cultured in situ and for
the clean up of the contaminated water.
• This research highlights the potential of algal biomass for use in metal
bioremediation.
• The results indicate that Oedogonium sp. is an effective biosorbent for Cu, Co,
Cr, Fe, Hg, Ni, Zn and U. The maximum adsorption capacity of untreated algal
biomass was found to have comparable values to the ones reported in
literature.
 Assess the adsorption performance of the algal biomass on column mode and
then use this biomass to monitor in situ the metals removal from polluted stream
draining artisanal gold mining - to test the efficacity of biological filters.

17. Acknowledgements
• Dr H. Tutu
• Prof E.Cukrowska
• THRIP
• Anglogold Ashanti
• Wits University