Dissolution of Slightly Soluble Sulfates by Ion Exchange Resin under Rate Control by Diffusion through Two Liquid Films surrounding Salt and Resin Particles

Abstract

Dissolution of slightly soluble sulfates (Ca and Sr) suspended in water by cation exchange resin in H⁺ form (Dowex 50 W) in a stirred vessel at 30°C was studied under the condition that mass transfer through the two liquid films adjoining salt and resin particles was rate-controlling.
Dissolution rate charts which relate bulk hydrogen ion concentration C_H to k_ra_rt, as a parameter α {=k_sa_s/ (k_sa_s+k_ra_r)}, are presented.
The resin-side capacity coefficients k_ra_r were determined under the condition that the salt-side resistance was negligible. The values of α and overall capacity coefficients K_a (=αk_ra_r) were determined graphically by comparison with the observed values of capacity coefficient for a wide range of salt to resin ratio (W₀/m) with the value estimated from the charts mentioned above. Using the observed linear relation between W₀/K_a and W₀/m, the values of k_ra_r0 and k_sa_s0 were determined from the slope and intercept, respectively, and the validity of K_a were confirmed. The mass transfer coefficients obtained from the measured capacity coefficients were well correlated as functions of operating variables such as resin and salt particle size and rate of agitation.