Self-heating activation energy and specific heat capacity of sulphide mixtures at low temperature

Energy of activation (Ea) and specific heat capacity (Cp) for mixtures of sulphide minerals that on their own do not self-heat (SH), sphalerite/pyrite, pyrite/galena, chalcopyrite/galena and sphalerite/galena, were determined using a self-heating apparatus at temperatures below 100 °C in the presence of moisture. The mixtures all gave Ea ranging from 22.0 to 27.8 kJ mol−1, similar to the range reported for Ni- and Cu-concentrates. The Ea is close to that for partial oxidation of H2S which adds to the contention that the partial oxidation of H2S contributes to SH of sulphides at low temperature. The Cp values ranged from 0.152 to 1.071 JK−1 g−1 as temperature rose from 50 °C to 80 °C, similar to the reported findings on Ni- and Cu-concentrates. The role of galvanic interaction in promoting SH is tested by examining correlations with the rest potential difference of the sulphides in the mixture.