Non-oxidative leaching of mechanically activated stibnite

Abstract The results obtained by leaching stibnite with a basic solution of sodium hydrogen sulphide are presented in this paper. The intensification of leaching by the mechanical activation produced by grinding the mineral in a planetary mill for 20 min brings about acceleration of the process by tenfold. The non-oxidative leaching of stibnite is a structure-sensitive process and the structure sensitivity decreases if assemblages of particles, i.e., agglomerates arise. The activation energy calculated from the temperature dependence of leaching in the region 293–345 K had the value E =28 kJ mol −1 for a non-activated sample (standard) and E =13 kJ mol −1 for a sample activated for 20 min. This suggests that the rate-determining step must have been changed. The SEM investigation of the residues after leaching documents the morphological non-uniformity of the leaching process.