Abstract
M.Tech. (Biotechnology)
Due to the depletion of rich ore bodies, the fact that conventional extractions become obsolete and uneconomical and additional stringency on environment related regulations, there is a call for cheaper and greener metal extraction methods. Through research and innovation, new developments and improvements of processes and products are required in both metallurgical and biological areas. As a result, research interests in the use of microbes in the optimization of metal recovery from low grade sulphide ores have grown increasingly popular. The involvement of microbes in the recovery process is thus dependent on the growth of the microbes, which is influenced by their physicochemical parameters. The availability of nutrient salts is thus essential for maintaining optimal growth, furthermore is the dependence of metal dissolution with nutrient quantities on substrate accessibility. Considering the “green chemistry” of some ionic liquids the important “technological”, “toxicological ” and “eco-toxicological” assessment of the risks related with ionic liquid design; choline based ionic liquids were selected by virtue of their low toxicity, low environmental persistence and readily biodegradable nature. As a result of the selective solubility strength of metal oxides in ionic liquids, choline based ionic liquids were considered novel media for obtaining target metals and improving bioleaching kinetics. The study thus sought to develop an economic and eco-friendly alternative technology, employing choline based ionic liquids as biocompatible substrates for the optimal recovery of base metals, improving bioleaching kinetics. Biological and molecular characterization of ultra-deep mine isolates (Gold 1 Mine East Rand, Springs Johannesburg, South Africa) revealed a halophilic community of gram positive and negative bacteria namely Raoultella ornithinolytica, Bacillus sp., Bacillus thuringiensis and Pseudomonas moraviensis. The halophilic bacterial strains indicated high biocompatibility in choline lactate, choline chlorite, choline dihydrogen phosphate, choline citrate and choline levulinate with poor biocompatibility noted in choline citrate and choline tartarate. According to literature, the biocompatibility of the leading choline based ionic liquids (ILs) was accredited to the quaternary- ammonium cation integrating a polar hydroxyl and the limited branching of the side chain. Prominent logarithmic growth in choline lactate was indicative of the metabolic advantage of choline lactate over conventional glucose sources. Furthermore, the bioleaching of BCL slag by Bacillus species and Bacillus...