Model development for estimating calcium sulfate dihydrate, hemihydrate, and anhydrite solubilities in multicomponent acid and salt containing aqueous solutions over wide temperature ranges

• Published in: Journal of molecular liquids Vol. 328
• Main Authors: Zarei, Mohammad Mehdi, Hosseini, Mostafa, Mohammadi, Amir H., Moosavi, Ali
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.04.2021
• Subjects: Anhydrite; Calcium sulfate solubility; CSA-LSSVM; Dihydrate; Hemihydrate; Pitzer ion interaction; CSA-LSSVM; Hemihydrate; Calcium sulfate solubility; Anhydrite; Pitzer ion interaction; Dihydrate
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2021.115473

Thermodynamic solubility of calcium sulfate in multicomponent electrolyte aqueous solutions is of significant importance in many disciplines in science and engineering. A knowledge of environmental chemistry and aqueous solubility of calcium sulfate and several of its hydrates; anhydrite (CaSO4), hemihydrate (CaSO4.0.5H2O), and dihydrate (CaSO4.2H2O); in acid and salt-containing media is of huge practical and theoretical importance. In this study, a solubility calculation model was developed based on coupling of Least Squares Support Vector Machine and Coupled Simulated Annealing (CSA-LSSVM) to model the solubility of various forms of calcium sulfate in aqueous solutions over wide temperature ranges. Comparing the model results to 3079 experimental data gathered from the literature yields a correlation coefficient of 0.9897 and RMSE of 0.0068. The model is able to present accurate solubility results for calcium sulfate dihydrate (CaSO4.2H2O) in aqueous solutions containing H2SO4, ZnSO4, CuSO4, NiSO4, MnSO4, H3PO4, NaCl, CaCl2, MgCl2, KCl, FeCl2, Na2SO4, HNO3, Ca(NO3)2, HCl, AlCl3, Ca(HCO3)2, NaNO3, LiNO3, Li2SO4, MgSO4, Al2(SO4)3, NaClO4, NaOH, KOH at temperatures up to 100 °C, calcium sulfate hemihydrate (CaSO4.0.5H2O) in solutions containing NaCl, CaCl2, MgCl2, KCl, FeCl2, HCl at temperatures up to 125 °C, and calcium sulfate anhydrite (CaSO4) in solutions containing H2SO4, NaCl, CaCl2, MgCl2, Na2SO4, HNO3, HCl, NaNO3, LiNO3, NiSO4, MgSO4, Al2(SO4)3, Mg(NO3)2 at temperatures up to 350 °C. Comparison of the CSA-LSSVM model results to those of Pitzer ion interaction model as well as BR-ANN model in binary, ternary, and multicomponent mixtures reveals the superiority of the CSA-LSSVM model developed in this study in all cases. •Two solubility models based on BR-ANN and CSA-LSSVM were developed.•Solubilities of calcium sulfate dihydrate, hemihydrate, and anhydrite in multicomponent electrolyte solutions are estimated.•A correlation coefficient of 0.9897 and RMSE of 0.0068 were obtained for CSA-LSSVM model.•Model results agree well with experimental solubility data.•CSA-LSSVM and Pitzer ion interaction models are capable of capturing the physical trends in experimental data.