NONOXIDATIVE LEACHING OF MECHANICALLY ACTIVATED STIBNITE

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.