Estimating activation energy from a sulfide self-heating test

Using a custom-designed self-heating apparatus and procedure, activation energy (Ea) was determined for four sulfide-bearing materials: two nickel concentrates, a copper concentrate and a sphalerite/pyrite mixture. The Ea ranged from 22–29 kJ mol−1, implying a common reaction. Comparing to literature, the Ea values correspond to partial oxidation of hydrogen sulfide, supporting the contention that H2S may be an intermediate product in the self-heating of sulfide minerals.

The plots of ln(SHR) vs. 1000/T for four sulfide samples resulted in strong linear negative relationships of Arrhenius type. The energy of activation (Ea = 21–30 kJ/mole) were calculated from the slopes and corresponded to Ea for partial oxidation of H2S. Ni-Conc = nickel sulfide concentrate, Cu-Conc = copper sulfide concentrate, ZnS/FeS2 = sphalerite/pyrite mixture, Rag = Raglan (Quebec, Canada), VB = Voisey’s Bay (Labrador, Canada).Figure optionsDownload as PowerPoint slideHighlights
► Activation energy (Ea) of sulfide self-heating (SH) was estimated.
► Custom-designed SH apparatus was used at temperatures below 100 °C with Moisture.
► Four sulfide materials gave same SH Ea.
► The Ea corresponded to partial oxidation of H2S.