Browsing by Author "Apsey, Grant"

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    Impurities in crystals formed by eutectic freeze crystallization
    (2011) Apsey, Grant; Lewis, Alison Emslie
    A large concern facing South African industry, particularly the mining sector, is a suitable and sustainable means to deal with large volumes of liquid waste, comprised mostly of effluent water streams containing a variety of dissolved salts. A novel technique is being developed for the treatment of industrial waste brines; Eutectic Freeze Crystallization (EFC), can potentially separate these into pure water and its major constituent salts, which can be reused or sold. The feasibility of this technology is heavily invested in its capacity to produce pure salts. Thus, it is important to investigate the obtainable purity of these salts, before larger scale operations can begin. A major component of many South African waste brines is sodium sulphate. This work has therefore focused on the purity of sodium sulphate obtained from two different South African brines.
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    Selenium impurity in sodium sulphate decahydrate formed by Eutectic Freeze Crystallization of industrial waste brine
    (The Southern African Institute of Mining and Metallurgy, 2013) Apsey, Grant; Lewis, Alison Emslie
    Eutectic freeze crystallization (EFC) is a novel technique for the recovery of pure salt and pure water from hypersaline waste brines. It is therefore a promising technology for the treatment of industrial waste waters. The impurities caused by crystallizing salt out of multi-component brines by EFC have not yet been investigated, however. To these ends, the selenium impurity found in sodium sulphate, produced from the waste brine of a platinum operation, was investigated. It was believed that the similarity between sulphate and selenate ions allowed isomorphous substitution of selenate ions into the sodium sulphate crystals, which was the likely cause of impurity uptake. It was found that the presence of sodium chloride in the industrial brine promotes the uptake of selenium, while ionic strength of the brine and mass deposition rate of sodium sulphate did not have a significant effect on the selenium uptake. Isomorphous substitution is predicted to be the most significant mechanism by which all impurities will be taken up when applying EFC to other industrial waste brines.