Preparation of Potassium Sulphate from Separation of Potassium and Sodium by Amine Extraction

The potassium sulphate was prepared by using the lixivium of sintered Aegirine-augite syenite as raw material.The lixiviated solution can be regarded as a simple KHCO3-NaHCO3-H2O ternary system and was treated with isothermal evaporation and crystallization at 60℃ until the mass ratio of sodium carbonate and potassium carbonate reaches about 2;then added the organic amine extraction system consisted of V(organic phase)/V(inorganic phase)=3.5:1 into the solution.Since the solubility of the K+ and Na+ in the organic phase-H2O miscible liquid system are significantly different,the well-distributed organic amine extraction system consisted of V(tri-butyl amine)/V(n-butyl alcohol)=1:2.5 was used to separate the K+ from Na+ in the carbonic solution.Under the temperature of 25℃,with stirring and injecting CO2 at rate of 0.15 m3?h-1 for 1.5 h,about 99% sodium carbonate could be separated out by the followed vacuum filtration.Finally,the potassium sulphate could be obtained by adding a certain amount of sulfuric acid into the filtrate.The results show that the product K2SO4 reaches the premium grades of agricultural potassium sulfate.