Silver leaching from miargyrite (AgSbS2) sulfosalt in the system S2O32--Ca(OH)2: Kinetic analysis and experimental design approach

This investigation reports the silver dissolution kinetics from a ore-type sulfosalt identified as miargyrite, which prevails in the chemical concentration process of polymetallic concentrates, in the S2O32--Ca(OH)2 system as well as a statistical study of the design of experiments concerning the effect of temperature (T), calcium hydroxide concentration ([Ca(OH)2]), thiosulfate concentration ([S2O32-]), particle size (d0) and stirring speed (RPM). The results show that temperature is the variable with the most significant effect on the dissolution rate of silver and obtains an activation energy (Ea) of 57.19 kJ mol-1, followed by particle size and hydroxide concentration. Furthermore, it was observed that stirring speed does not affect the dissolution rates in basic medium. These results are consistent and demonstrate that the dissolution reaction is controlled by the chemical reaction. The study of the factorial design was relevant to elucidate the behavior of the variables with the greatest impact in the experimental kinetic study. Finally, kinetic and statistical models were proposed to describe the silver dissolution process in an alkaline medium. The highest silver dissolution was achieved using the following conditions V = 0.5 L, mineral = 40 g L-1, PO2 = 1 atm, t = 360 min, d0 = -105 + 74 μm, [S2O32-] = 0.5 mol L-1, [Ca(OH)2] = 0.05 mol L-1, T = 338 K and RPM = 670 min-1.