Leaching of Natural Stibnite Using Na2S and NaOH Solutions

Abstract

First stage of the hydrometallurgical production of antimony is leaching of the raw material that contains antimonybearing mineral. The raw material can be ore or concentrate. Leaching can be carried out either in alkaline (Na 2 S+NaOH; NaOH) or acid (HCl; H 2 SO 4 ; HF) solutions. In order to achieve good antimony recovery it is essential to leach the raw material under optimum conditions.Kinetics of the reaction between particulate stibnite and mixed Na 2 S + NaOH solutions were studied. The effects of concentrations of Na 2 S and NaOH, temperature, particle size and liquid-to-solid ratio were investigated. It was observed that the rate of leaching of stibnite: a) increased with an increase in both Na 2 S and NaOH concentration (from 0.5 wt. % to 2.0 wt. %), and temperature (from 292 K to 327 K); b) reached its maximum at Na 2 S: NaOH weight ratio equal to 1:1; c) decreased with an increase in particle size (from 40 m to 500 m) and L/S ratio (from 10 to 100). The results are presented in terms of the shrinking (nonreacted) core model and shrinking porous-particle model. Apparent activation energy is approximately 44 kJ mol -1 and the apparent reaction order for Na 2 S varies from 1.4 to 1.7. Calculated values of the kinetic parameters indicate that the leaching process is controlled by both intrinsic chemical reaction between Sb 2 S 3 and Na 2 S at the liquid/solid interface, and pore diffusion.