Pyrite–water interactions: Effects of pH and pFe on surface charge

Interfacial properties of pyrite–water suspensions were examined by potentiometric titrations. Initial experiments show that the dissolution of pyrite occurs even under anaerobic conditions. The role played by H+, OH−, Fe2+ and S2− as potential determining ions (PDI) on surface charge development was also assessed. The pHzpc of pyrite was experimentally determined at 1.7. When pH = pHzpc, the pFezpc of pyrite was 2.97. A 1-pK diffuse-layer model (1-pK DLM) quantified proton titration data using following reaction stoichiometries: 〉 FeS S − 1 / 3 + H + → FeSS H + 2 / 3 log   K = 0.93 ± 8.34 E − 02 〉 FeS S − 1 / 3 + 2 H + → HHS S − 1 / 3 + F e 2 + log   K = − 2.87 ± 0.77 〉 FeS S − 1 / 3 → F e 2 + + 〉 S S − 5 / 3 log   K = − 2.90 ± 0.12