The solubility of CaMoO4(c) and an aqueous thermodynamic model for Ca2+-MoO 4 2 -ion-interactions

The solubility of powellite [CaMoO4(c)] was studied in aqueous Na2MoO4, CaCl2 and Ca(NO3)2 solutions ranging in concentrations from 1×10−4M to 1.0M and over equilibration times extending to 36 days. Our experimental data were interpreted using the aqueous ion-interaction model of Pitzer and coworkers. The Ca2+−MoO 4 2− ion-interactions were found to be analogous to Ca2+−SO 4 2− . The use of Ca2+−MoO 4 2− ion-interactions parameters (β(0)=0.2, β(1) = 3.1973 and β(2)) and a logK sp of −7.93 gave excellent predictions of all of the experimental data. Commonion ternary interaction parameters such as MoO 4 2− −Cl− or MoO 4 2− −NO 3 − were not required.