The effect of chloride on the solubility of calcite and dolomite

With the PHREEQC software,the solubility of calcite and dolomite in the NaCl,KCl,CaCl2,and MgCl2 solution under non-air and atmospheric P CO2 conditions is simulated.The results indicate that the solubility of calcite in NaCl,KCl and MgCl2 solution and the solubility of dolomite in NaCl and KCl solution are much larger than those in pure water.The primary reason for this is the salt effect function.Because of the common ion effect,CaCl2 can reduce the solubility of calcite.The solubility of dolomite in higher concentration of CaCl2 or MgCl2 solution is higher than it is in pure water,in spite of the common ion effect and the dolomitization in CaCl2 solution exist.Simulation still reveals that dolomitization and dedolomitization will take place in the calcite dissolved in MgCl2 solution and in the dolomite dissolved in CaCl2 solution,making the incongruent dissolution continue to happen.Among the routine ions,the important sequencing of the improvement solubility of the calcite and dolomite functions is that as for calcite dissolution,the effect of anion SO 2-4 is greater than that of Cl-,the effect order of the ions in the system is Mg 2+ >Na+>K+ >Ca 2+.As for dolomite dissolution,the effect of anion SO 2-4 is greater than that of Cl-,while the effect of ion is determined by P CO2 and concentration of CaCl2.When P CO2 =0 or when P CO2 =10-3.5 bar and the concentration of CaCl2 is lower than 1.5mol/L,the effect order of the ions in the system is Na+>K+ >Ca 2+ >Mg 2+.When P CO2 =10-3.5 bar,and concentration of CaCl2 is higher than 1.5 mol/L,the effect order becomes Ca 2+ >Na+ >K+>Mg 2+.