Sulphoxy anions in recycled flotation process waters possess the potential to reduce the flotation efficacy of flotation reagents. In this study, dithionite ions and their interaction with thiol collectors in solution and the surface modifications of galena and chalcopyrite surfaces in the presence of dithionite ions were investigated. Microflotation tests, zeta potential tests, electrochemistry studies, solution xanthate degradation kinetics and surface analyses were carried out.

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... results showed a reduction in chalcopyrite and galena recoveries in dithionite solutions even in the presence of xanthate. Zeta potential and rest potential measurements showed that the potential determining effect of dithionites on the sulphide mineral surfaces (zeta potentials) and the solution (pulp potential), inherently decrease collector-mineral interactions. Xanthate degradation tests showed that more than half of the collector in solution was consumed in 10 min of reacting 20 mg/L of xanthate with 500 mg/L of dithionites. Surface analyses results also revealed that dithionites strongly influenced the chemical state of the sulphide minerals under investigation by producing oxidised sulphur species in the form of sulphites on the galena surface and oxidised iron species in the form of oxides and hydroxides on chalcopyrite. The current study presents a complete view of dithionite behaviours in plant waters by considering the dithionite-mineral surface interactions and dithionite-collector interactions in addition to the traditionally agreed on pulp potential alterations.