LEACHING OF STIBNITE BY MIXED Na2S AND NaOH SOLUTIONS.

Kinetics of the reaction between particulate stibnite and mixed Na2S + NaOH solutions were studied. The effects of concentrations of Na2S 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 Na2S and NaOH concentration (from 0.5 wt. % to 2.0 wt. %), and temperature (from 292 K to 327 K); b) reached its maximum at Na2S:NaOH molar ratio equal to 1:2; c) decreased with an increase in particle size (from 0.04 mm to 0.5 mm) and L/S ratio (from 10 to 100). The results are presented in terms of the shrinking-particle model. Calculated values of the kinetic parameters indicate that the leaching process is controlled by the chemical reaction between Sb2S3 and Na2S at the liquid/solid interface. Apparent activation energy is approximately 44 kJ mol-1 and the apparent reaction order for Na2S varies from 1.4 to 1.7. [ABSTRACT FROM AUTHOR]