Recycling of process water and influence of its chemistry on sulphide flotation
Recycling of flotation effluents through the ore processing plant is one of the ways of reducing both plant operating costs and industrial impact onto the local ecosystem.
Such waters, named acid mine drainage (AMD), if discharged from sulfide flotation are highly saturated with calcium and sulfate species and have a high salinity. As minor species, they commonly contain reduced sulfur compounds (RSC) (sulfooxyanions with sulfur in the oxidation state below VI) which arise due to the use of sodium bisulfite as a flotation depressant, cations of ferrous and non-ferrous metals, frothing molecules, residual chemical reagents and products of their degradation. The key step towards developing scientific approaches of recycling of the tailing waters is elucidation of how, in what extent, and why the AMD components, taken signly or together, influence flotation of sulfides. The influence of these species at concentrations typical for tailing ponds on the adsorption-oxidation-desorption reactions of the collectors with the sulfides is being investigated in the project. The knowledge generated will assist to selectively regulate surface properties of sulfides in flotation
Objectives
The on-going project aims to elucidate the influence of major species of sulphate and calcium ions at concentrations typical for process water and tailing ponds on the adsorption of collectors and mixture of collectors onto pyrite, galena, sphalerite and chalcopyrite in simple and multi-sulphide systems.
Approach
The interaction of collector and pure minerals were studied in the presence and absence of flotation effluent through, adsorption, zeta-potential and spectroscopic studies as well as through Hallimond flotation of pure minerals and bench scale flotation of complex sulphide ores using both fresh and process water
Results and conclusions
The effect of calcium ions in flotation solution has greater dominance than sulphate ions, high zeta-potentials of pyrite, chalcopyrite and galena in the presence of calcium ions in solution is an indication of possible better adsorption of anionic collectors on the minerals which will ultimately lead to the minerals activation during flotation. However other transition metal species in combination with calcium and sulphate species also found in process water interacts in a complex way and ultimately activates sphalerite but still depresses chalcopyrite and galena.
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