Salt recovery from wastewater by air-cooled eutectic freeze crystallization

Due to stringent legislation, wastewater needs to be treated before dispersing in the environment. Wastewater can be purified through the formation of less contaminated ice layer by freezing. Freezing of the wastewater leaves the remaining wastewater more concentrated. Attainment of eutectic point (both ice and soluble salt crystallize simultaneously) by freeze crystallization can add extra financial value in terms of salt recovery. Separation of ice from salt becomes very easy because of significant density difference. Na₂SO₄ is one of the key components present in wastewater emanating from different industrial sources, considered as a model compound in this study. Recovery of Na₂SO₄ from the aqueous solution by eutectic freeze crystallization air-cooled through the ice layer and solution surface is an energy-efficient and cost effective method. This method was investigated experimentally to recover Na₂SO₄ from its solution. Furthermore, the influence of different factors and operating conditions was studied on the efficiency of the purification and recovery process.