Dissolution kinetics of galena in acid NaCl solutions at 25-75 °C

Experiments on dissolution kinetics of galena were performed in 1 mol 1(-1) NaCl solutions at pH 0.43-2.45 and 25-75 degreesC. When the dissolution reaction is far from equilibrium, a linear relation exits between the dissolution rate, r, and the H ion activity, [H+]. The rate law for galena dissolution is given by the following equation: r = k[H+]. With respect to H the dissolution reaction is in the first order. The apparent rate constant, k, has values of 2.34 x 10(-7) mol m(-2) s(-1) at 25 degreesC, 1.38 x 10(-6) mol m(-2) s(-1) at 50 degreesC, and 7.08 x 10(-6) mol m(-2) s(-1) at 75 degreesC. The activation energy of dissolution reaction is 43.54 kJ mol(-1). The mechanism of dissolution is suggested to be surface chemical reaction, and the rate determining step is the dissociation of the Pb-S bond of the surface complex, which releases Pb2+ into the solution. (C) 2003 Elsevier Ltd. All rights reserved.