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.

M. Tech. Chemical Engineering. / Discusses the reactive properties of oxalate molecules on the surface of activated carbons (ACs) so that they can bind selectively with base metals. Therefore, the experimental plan covered three main axes of study: Chemical modification of AC adsorbent and characterization, adsorption studies in batch and continuous modes, and adsorption modelling.

Organic molecules such as amino acids have long been considered the cause of some anomalous behavior of metals in the marine environment, with respect to concentration in the water and adsorption on the sediment. Many studies have investigated the adsorption of amino acids and amino acid complexes. This study investigates the adsorption of cobalt, amino acids, and cobalt amino acid complexes on both Na⁺-montmorillonite and Na⁺-birnessite (MnO₂). Amino acids were also adsorbed on Co²⁺-saturated montmorillonite and birnessite. The oxidation state and chemical nature of sorbed cobalt and the chemical nature of the amino acid amine groups were investigated using x-ray photoelectron spectroscopy (XPS). XPS enabled determination of the stoichiometry of the sorbed complexes. Electrophoresis revealed changes in the surface charge of the substrate upon interaction with cobalt, amino acids, and cobalt amino acid complexes. These changes provided insight into the reaction mechanisms and chemical species involved. Infrared and visible spectroscopy, x-ray diffraction (XRD), and quantitative analysis enabled further determination of the reactions that occurred between cobalt, amino acids, cobalt amino acid complexes and the sediment surfaces. Using XPS, it was found at pH values 4 to 7 that Co(II) adsorbed on montmorillonite as Co(II) and on birnessite as Co(III). The birnessite (MnO₂) surface was determined to be the oxidizing agent. XPS, XRD, and infrared spectroscopy indicated that amino acid adsorbed on montmorillonite by cation exchange, keying into octahedral sites, and by peptide formation. Increased adsorption was observed on Co²⁺-montmorillonite in solutions of both glycine and lysine and was attributed to coordination reactions. Both Co(gly)₃ and Co(lys)₃³⁺ complexes were observed in solution and were either formed on the clay surface and released, or desorbed cobalt was complexed in solutions. Co(lys)₃³⁺ was observed on the clay surface following interaction of Co²⁺-montmorillonite with lysine. It is proposed that dissolved oxygen oxidizes cobalt in the amino acid complexes. XPS and electrophoretic mobility measurements indicated that amino acids interact with birnessite by chelation of the surface manganese. Measurement of the Mn 3s splitting for amino acid saturated birnessite samples showed that the surface was reduced. It was inferred that the manganese dioxide surface oxidizes amino acids, but no proof of oxidized amino acids was obtained. Hydrolysis of complexes was observed on both the manganese dioxide and montmorillonite surfaces. Because these complexes are known to be relatively stable to hydrolysis in solution, it was proposed that the surface catalyzed the hydrolysis. The oxidation state and chemical nature of selected metals in Pacific manganese nodules were investigated using XPS. Analysis of binding energies, shake-up satellite features, and multiplet splittings revealed that the oxidation states for the metals in the nodules were Mn(IV), Fe(III), Co(III), Pb(II and IV), Cu(II), Ni(II), and Ti(IV). / Doctor of Philosophy