Phase Diagram for the Na₂SO₄–(NH₄)₂SO₄–MEA–H₂O System at Elevated Temperature

Abstract

It is essential to develop a new antisolvent technology for soda ash manufacture by the use of sodium sulfate as raw material due to intensive energy consumption for the separation of sodium sulfate from ammonia sulfate-bearing liquor by filtering sodium bicarbonate. Phase diagram data for the Na2SO4-(NH4)(2)SO4-monoethanolamine (MEA)-H2O system was determined and modeled to regress the paired-ion interactions included in the mixed-solvent electrolyte model with good accuracy. It was found that the solubility of Na2SO4 in MEA solution sharply decreases with the concentration of MEA, while the addition of MEA as the solvent largely enhances the solubility of (NH4)(2)SO4 in solution. These findings show that sodium sulfate may be efficiently separated from ammonia sulfate solution with the help of MEA antisolvent technology.