Abstract:Impurity of magnesium carbonate (MgCO3) was studied with nitrilotriacetic acid as ligand. Thermodynamic equilibrium equation of Mg2+-CO32--Nta3--H2O system was established, and thermodynamic equilibrium diagram was drawn to investigate selectivity of Nta3- on magnesium under total concentration of Nta3- of 0~2.5 mol/L and pH value of 5~14. The results show that dissolution of MgCO3 under acidic condition is mainly upon effect of H+, while dissolution of MgCO3 under alkaline condition is mainly due to coordination reaction between Mg2+ and Nta3?. However, dissolution quantity of MgCO3 is very low in alkaline system because coordination ability of Mg2+ with Nta3- is very weak. Alkaline nitrilotriacetic acid system has high selectivity to magnesium in minerals.