Includes bibliographical references (p.84-87). / The zinc oxide resource of Skorpion Zinc, an integrated zinc mine and refinery, near Rosh Pinah in southern Namibia, will be depleted by end of 2015 with a possible extension to 2017. Extensive exploration drilling was unsuccessful. With the abundant availability of zinc sulphide concentrates regionally the life of the operation may be extended by processing these concentrates. The leach kinetics of zinc sulphides is vastly slower than oxides, preventing the processing of zinc sulphides using the existing process, under current conditions. The challenge is to identify a suitable zinc sulphide treatment process that can be integrated with the existing plant. Information from the bench scale test work and an update of the economic models will provide sufficient accuracy for Skorpion to select either the pressure or the atmospheric leach process.

Includes bibliographical references (leaves 63-65). / Anglo Research (AR), a division of Anglo Operations Limited, is developing a chloride-based processing route for the recovery of zinc from sulfide ores. The Anglo Research Zinc (tARZn) process incorporates a chloride leach. Solvent extraction (SX) is being considered as a potential leach liquor purification option for the process. It is envisaged that the pregnant leach solution (PLS) will be sent to SX after which zinc will be recovered as plate metal and chlorine gas generated from an electrowinning step.

The purpose of this work was to identify promising microalgal species and strategies of nitrogen deprivation that optimise lipid productivity for biodiesel production. This was carried out by I) developing the tools necessary to measure lipid productivity accurately, II) identifying and quantifying the key characteristics of promising microalgal strains, initially through a literature survey and then experimentally, and III) investigating the effect of different degrees of N limitation, and different N culture regimes, on cell physiology and lipid productivity in Chlorella vulgaris.

Includes abstract. / Includes bibliographical references. / Namakwa Sands is a heavy mineral mining and beneficiation business within Tronox, and produces two major products, zircon (zr02.Si02 99.9%) and rutile (Ti02 99.9%) at a combined annual rate of 140kt. The heavy mineral concentrates are exported to international markets to make specialist coatings for the paints and ceramics industries. The ceramic industry is very strict on the purity of the minerals used. Namakwa Sands prides itself in being able to produce zircon and rutile at these requirements; however, strict requirements, especially in terms of Fe impurities (Fe203 content in zircon concentrate must be < 600ppm), limit the productivity and come at a cost to recovery. The concentration and separation of heavy minerals is a complex process, which utilizes conductivity differences between minerals. Zircon coated with iron oxides (Fe203, FeOOH) reports as more conductive during electrostatic separation, which can result in a zircon particle to behave like a rutile particle and in this way cause both products (rutile and zircon) to become off specification.

Includes abstract. / Includes bibliographical references (p. 127-138). / This thesis presents the investigation of the production of a novel thermostable amidase (EC 3.5.1.4) from Geobacillus pallidus RAPc8 using recombinant E.coli BL21 (DE3). The choice of growth medium and induction strategy were optimised under bioreactor conditions to enhance amidase productivity. Further, expanded bed adsorption (EBA) was assessed as a tool for minimising the unit operations in the amidase purification train. The EBA process can integrate up to four steps by merging processes involved in centrifugation, microfiltration and initial adsorption into one unit operation.

This dissertation presents the results of an investigation to develop a two-stage flotation process to produce: (i) a low-volume sulfide-rich concentrate that can be treated chemically or biologically or disposed of in a contained manner; (ii) a high-volume (low sulfur) benign tailings, with low ARD potential compared to conventional tailings; and (iii) a coal concentrate that has added value on account of its low sulfur and ash content. Success requires integration of flotation, aqueous chemistry and mineral bioleaching expertise. The approach adopted in this exploratory study entails coal flotation in the first stage, which takes advantage of its natural hydrophobicity.

The aim of this study is in two parts; the first part focuses on mineralogical quantification of the extent of weathering at PPM by profiling the flotation behaviour and host rock density with spatial depth.

Includes abstract. / Includes bibliographical references. / This thesis focuses on the application of the high pressure grinding rolls (HPGR) on platinum bearing ores Merensky, UG2 and Platreef. Conventional tumbling mills such as the ball mill that are typically applied on these ore types are highly energy intensive with a small percentage of the input energy being used for actual breakage. Rapidly increasing energy costs have contributed to the rising interest of the HPGR in the platinum industry, particularly in plants processing UG2 and Platreef ores. Therefore, this thesis seeks to determine if the HPGR can be used as an alternative to the ball mill. Key aspects of interest are throughput, energy efficiency, PGE grade and recovery and PGM liberation.

Includes bibliographical references (leaves 104-115). / Chalcopyrite is the most abundant primary copper sulphide mineral found worldwide. As copper grades of ores available for extraction decrease, heap bioleaching is gaining interest as a potential operating alternative to traditional methods of roasting and smelting. The efficiency by which bacteria assist leaching chalcopyrite is governed by their interaction and association to the sulphide mineral in the ore. While both planktonic and mineral-associated micro-organisms contribute to the bioleaching of mineral sulphides through the oxidation of ferrous iron little information exists as to their ability to adhere and leach low grade chalcopyrite ore. This study was undertaken to determine the association of defined and mixed microbial species on a chalcopyrite concentrate and a chalcopyrite ore. At. ferrooxidans, At. caldus, At. thiooxidans and L. ferrooxidans were grown in pure culture and used to investigate the mineral-microbe association within defined experimental parameters of two experimental operations.

Includes bibliographical references (leaves 67-73). / The formation of acid mine drainage (AMD) from the microbial oxidation of sulfides in mineral waste deposits is one of the major challenges facing the mining industry worldwide. Growing environmental awareness and subsequent changes in legislation has focused research in addressing the prevention of pollution by AMD. Current waste management approaches focus on deposition techniques to control AMD formation and on remediation. However, these approaches do not remove the risk of AMD generationand are yet to be proven effective in mitigating long-term acid generating potential. Incompliance with the principles of pollution prevention, addressing waste at its source,the aim of this work is to remove the risk of AMD generation by focusing on theremoval of sulfides from potentially acid generating tailings prior to disposal.