Single-stage process for manufacturing of potassium sulphate from sodium sulphate

A single-stage process for the conversion of sodium sulphate (anhydrous or hydrated, of natural or anthropogenic origin) with potassium chloride in aqueous solution at 20-25 degrees C to potassium sulphate was developed. Both reagent grade sodium sulphate and that formed as a by-product during trimethylolpropane, synthesis were used as raw material. Initial reaction mixture contained less than 30 mass % of salts with the calculated mole ratios n(KCl) : n(Na(2)SO(4)) >= 6; n(K(2)SO(4) : n(NaCl) >= 1. Resulting potassium sulphate contained about 96 mass % of K(2)SO(4), 0.5 mass % of Cl(-), and 0.2 mass % of Na(+). At the first stage, a mixture of potassium chloride with glaserite was separated from the mother liquor after the separation of K2SO4 through solvent evaporation followed by crystallization at temperatures <= 2 degrees C. During the second stage, sodium chloride was separated from the solution obtained after the solvent evaporation and crystallization at 110 degrees C. Both, the mixture of KCl and K(3)Na(SO(4))(2) and the remaining end-liquor were recycled to the conversion stage. Raw sodium chloride was a by-product formed in the process.