M.Sc. / Inorganic pollutants like heavy metals are some of the major water pollutants worldwide. They are toxic and in some cases carcinogenic even at low concentrations. Their removal from industrial aqueous solutions, wastewater and hydrometallurgical process solutions prior to their release to the environment is necessary for a healthy biosphere which includes human beings, aquatic life and plants. There are several technologies used to remove metals such as Cu, Co, Zn, Hg from water. These include among others, ion exchange, membrane filtration, activated carbon, electrochemical treatment, chemical precipitation, reverse osmosis, coagulation and flocculation. Although they have been used in the removal of metal pollutants from water, these technologies produce high quantities of sludge. They are also expensive to operate and need well trained personnel to operate large chemical plants. Since current metal removal techniques have limitations, a need exists for the development of environmentally friendly and cost effective techniques for the removal of metal ions from aqueous media. The focus of this research project is on the use of micro-organisms as biosorbents for copper and cobalt pollutants in aqueous solutions. The experimental work was carried out on a laboratory scale and a summary of our findings is presented as follows: Synthetic sulphate solutions of copper and cobalt were prepared using CuSO4. 7H2O and CoSO4. 5H2O powders. Concentrations of 0.002 M, 0.07 M and 0.2 M copper and cobalt ions in solution were used as test synthetic solutions for our experiments. Mixed strains of bioleaching bacteria were sourced from Mintek (Randburg, South Africa) to test the viability of this research project. This consortium contained Acidithiobacillus caldus, Leptospirillum spp, Ferroplasma spp and Sulphobacillus spp. These bacteria were able to remove up to 55% copper and 25% cobalt from low concentrated copper and cobalt sulphate solutions with 69% and 58% removal demonstrated in the case of mine effluents emanating from metallurgical operations. Different strains of micro-organisms (bacteria) were isolated from mine dumps and mine operation effluents and soil from the Palabora Mining Company in Limpopo, a northern province in South Africa and Nigel Town in the Gauteng Province. The isolated bacterial strains were then identified using PCR analysis and strains from the Bacillus genre were found to be predominant. Shewanella spp was also present. Pseudomonas spp was isolated using Pseudomonas agar base. These bacteria were then cultured at different species-specific culture conditions and their capabilities to remove copper and cobalt ions first from synthetic solutions and subsequently from mine effluents emanating from metallurgical operations were tested. In the first stage of biosorption experiments, factors that affect biosorption mechanisms which include, solution concentration, biomass concentration, pH, contact time and the presence of other metal co-ions were investigated. A decrease in the amount of metal sorbed as solution concentrations increased was observed with all the bacterial strains. An increase in metal sorption was also observed when biomass concentration was increased. The pH was found to be a species dependant parameter.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:6711 |
| Date | 31 March 2010 |
| Creators | Dlamini, Nonjabulo Prudence |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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