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The ExtrEL process promises to be a cost-effective and very energy efficient solid sulphur-rich mining waste dissolution technology. The process produces a uniform acidic matrix which can then be blended with appropriate metal, acid and water recovery technologies to develop an integrated processing circuit. This circuit could be modular in design, and thus relatively easily transported and installed to function on small remote sites with easy waste resource access, perhaps even powered by a local Green Energy source.
The process applies basic acid dissolution chemistry with minimal energy input to drive combination oxidation-reduction reactions which dissolve the sulphur-rich pyrite and pyrrhotite minerals in the tailings wastes. The combined reactions produce a process stream high in dissolved iron, and a waste stream of hydrogen sulphide which can be converted using existing technologies to either elemental sulphur or sulphuric acid.
The breakthrough ExtrEL process dissolves nickel from tailings. The nickel, in concentrations approaching 1.0% in both active and closed mill wastes, can be separated from the acidic solution matrix.
Unoptimized bench-scale trials of ExtrEL to date have provided over 75% recoveries of nickel occluded in the pyrrhotite waste from a Sudbury Tailings stream sample.
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