Kesieme, Uchenna K (2015) Mine waste water treatment and acid recovery using membrane distillation and solvent extraction. PhD thesis, Victoria University.

Abstract

Waste waters produced and disposed of at modern mine sites are problematic because they contain hazardous substances (e.g. heavy metals, metalloids, acids, process chemicals), and therefore require treatment before disposing to the environment. Three different kinds of mine waters are identified depending on their chemical composition and pH. They are acidic mine waters, alkaline mine waters and neutral mine waters. Acidic mine waters are of interest because they have greater environmental hazards compared to others. Other acidic waste solutions also considered are waste streams from mineral processing plants and smelter sites. The current approaches to manage acidic waste solutions includes, neutralization, flocculation, filtration and bioremediation. However, acid and water recovery using current technologies has not proven to be viable as most of these processes fail to produce sufficient volume and quality of water whereas others do not provide the selectivity necessary to create valuable product streams suitable for recycle or re-use. In these processes, the by-product sludge can itself become a disposal problem. Therefore a novel approach to acid and water recovery are needed to improve the sustainability of the mining industry. The objective of this study is to explore the possibility for the novel combination of two technologies, membrane distillation (MD) and solvent extraction (SX) for water and acid recovery. The focus is the testing on acid and water recovery from industry spent acid streams and acidic mine wastes solutions and also modelling of the economic opportunities for MD to understand its cost sensitivities, in particular in the context of a carbon tax benchmarked against its more well-known application in seawater desalination.

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