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:〉FeSS−1/3+H+→FeSSH+2/3logK=0.93±8.34E−02〉FeSS−1/3+2H+→HHSS−1/3+Fe2+logK=−2.87±0.77〉FeSS−1/3→Fe2++〉SS−5/3logK=−2.90±0.12