The Solubility And Stability Of Nesquehonite (MgCO₃·3H₂O) In Electrolyte Solutions

Magnesium is recovered by precipitation of nesquehonite which was prepared by the reaction of analytical pure MgCl₂ with Na₂CO₃.This magnesium mineral compound,was selected as a target precipitate due to its good filtration properties. Nesquehonite upon calcination yields high quality magnesium oxide(MgO).In this work,the solubility and stability of nesquehonite(MgCO₃·3H₂O) in several salts(NaCl,NH₄Cl,MgCl₂,KCl,LiCl and NaCl +MgCl₂,NH₄Cl +MgCl₂, LiCl+MgCl₂ mixed solutions) over the temperature range of(15 to 50)℃were determined.The concentration investigated for all salts was up to 4 mol·L^-1 NaCl,3.5 mol·L^-1 NH₄Cl,4 mol·L^-1 MgCl₂,1.0 mol·L^-1 KCl,1.5 mol·L^-1 LiCl at ambient temperature.The solubility of nesquehonite in pure water was found to decrease with temperature within the temperature range in which nesquehonite is the stable phase. In NaCl solutions,the solubility of nesquehonite initially increases to a maximum value and then decreases gradually with increasing of the common salt concentration. It was further found that the addition of MgCl₂,NH₄Cl,KCl or LiCl causes the solubility of nesquehonite to increase due apparently to complexation.In mixed solutions(NaCl + MgCl₂,NH₄Cl + MgCl₂,LiCl,and LiCl + MgCl₂),the solubility of MgCO₃·3H₂O phases was found to increase with the temperature increment.The comparison of the solubility of nesquehonite(MgCO₃·3H₂O) in H₂O,NaCl, NH₄Cl,MgCl₂ solutions between OLI prediction and experimental data was determined.The solubility of nesquehonite in water is in agreement with the prediction at appropriate temperatures.In NH₄Cl solutions,the relative deviation of the solubility of nesquehonite(MgCO₃·3H₂O) is below 5%.In NaCl and MgCl₂ solutions,a significant deviation of prediction from experiments was observed at the concentrated solutions.