The leaching of celestite in sodium carbonate solution

Abstract

The conversion reaction of strontium sulfate to strontium carbonate in sodium carbonate solution was investigated from both a thermodynamic and kinetic point of view. It is concluded that the conversion reaction is feasible. The effect of stirring rate, particle size of the celestite, temperature and the concentration of Na 2CO 3 and Na 2SO 4 on the leaching kinetics was studied. Based on the experimental observations, a mechanism for the leaching process is proposed. It has been found that the initial rate of conversion is governed by surface reaction. As the reaction proceeds, a dense layer of strontium carbonate forms on the celestite surface. This changed the rate controlling step to one of diffusion through a product layer. It is proposed that the diffusion of the sulfate ions through the strontium carbonate layer is rate determining. The apparent activation energies for the surface reaction and diffusion step are 71.5 and 64.1 kJ mol −, respectively.