Model study of pyrite demineralization by hydrogen peroxide oxidation at 30 °C in the presence of metal ions (Ni2+, Co2+ and Sn2+)

Dissolution of pyrite involving oxidation by hydrogen peroxide (H2O2) in the presence of metal ions (Ni2+, Co2+ and Sn2+) has been investigated. Before oxidation, pure and well crystalline structure of the acid washed pyrite sample, used in the present investigation, was confirmed by X-ray diffraction and chemical analysis. Oxidation of pyrite was examined by the determination of soluble sulfur. The rate of oxidation of pyrite with H2O2 is best represented by determining the rates of total soluble sulfur production. Each experiment was carried out for short (1-4 h) and extended (24 h) time periods. Pyrite is oxidized by H2O2 (1:1) up to the extent of 31.3% at short time period, which however remained the same even at extended time period. Increased amount of soluble sulfur has been observed when pyrite was oxidized by H2O2 (1:1) in the presence of Ni2+ or Co2+ or Sn2+ ion at short time period. The effectiveness of these metal ions in relation to pyrite oxidation at short time period decreases in the order Co2+>Sn2+>Ni2+, while at extended time period the order is Co2+>Ni2+>Sn2+. With Co2+ ion, the highest pyrite oxidation is obtained both at short (34.0%) and extended (35.0%) time period, while it is the lowest 31.3% with Ni2+ ion at short time and 25.3% with Sn2+ ion at extended time period. The effect of chloride ion on the rate of oxidation of pyrite is not pronounced in the metal ion containing systems. Substantial depletion in the concentration of externally added metal ions is in good agreement with the level of oxidation and infers certain adsorption or precipitation of metal ions on pyrite surface. The results of this study throw a new light of the influence of metal ions in the dissolution of pyrite in oxidation systems and has considerable applications in fields of demineralization, desulfurization and environmental science.