Removing Calcium And Magnesium From Heavy Metal Hydrometallurgical Process Based On Phase Chemistry

The scaling of calcium sulfate and magnesium sulfate in the heavy metal hydrometallurgical process has always been unresolved for the scientists in the world. Plenty of extensive researches have been carried out, but current data does not meet the requirements of solving the scaling of calcium and magnesium. Therefore, it is of great significance to carry on systematic researches on the solubility of anhydrous calcium sulfate in heavy metal sulfate solutions. In this paper, solubility phase equilibrium of anhydrous calcium sulfate were studied in the ternary systems CaSO4-CuSO4-H2O at 348.15 K、363.15 K、368.15 K, and CaSO4-MSO4-H2O (M=Zn, Mn, Mg) at 348.15 K、363.15 K by the isothermal method of equilibrium, and the solubility phase diagrams were drawn.The isothermal solubility phase diagrams of the ternary systems showed that, the temperature and the concentration of sulfate made an impact on the solubility of anhydrous calcium sulfate in the systems CaSO4-MSO4-H2O (M=Cu, Zn, Mn, Mg). In the condition of high temperature from 348.15K to 368.15K, firstly, the solubility of anhydrous calcium sulphate droped sharply to a minimum. Then, with the increasing of the concentration of the sulfates, the solubility of anhydrous calcium sulfate also strongly increases to a maximum. In more concentrated sulfate solutions, however, when the concentration of the sulfates continues to increase, the solubility of anhydrous calcium sulfate slightly decreases. While the concentrations of every sulphate are the same, the solubility of anhydrous sulfate was depressed with the increase of the temperature. The solubility of anhydrous calcium sulfate is lower than that of calcium sulfate dehydrate in the sulfate systems according to the comparison of the isothermal solubilities, which is of great significance in the building of new technology to avoid the scaling of calcium sulfate and the reduction of the calcium content in sulfates. Based on the reported experimental results and our phase diagrams about the solubility of calcium sulfate at different temperatures in relevant systems, a new technology is proposed to solve the crystal of calcium sulfate in zinc hydrometallurgy in this paper, and good results have been achieved on removing calcium under the laboratory conditions.