Kinetics of leaching of stibnite by mixed Na2S and NaOH solutions

The kinetics of the reaction between particulate stibnite and mixed Na2S + NaOH solutions were studied. The effects of the concentration of the Na2S and NaOH (from 0.5% to 2.0%), temperature (from 292 K to 327 K) and particle size (from 40 μm to 500 μm) were investigated. The results are presented in terms of the shrinking (non-reacted) core model and the shrinking porous-particle model. The apparent activation energy was approximately 44 kJ mol− 1, and the apparent reaction order for Na2S varied from 1.4 to 1.7. The calculated values of the kinetic parameters indicate that the leaching process is controlled by both the intrinsic chemical reaction between Sb2S3 and Na2S at the liquid/solid interface and pore diffusion.