For sodium sulfate waste, foreign countries mainly treat it by discharging it into the sea, with limited research on its resource utilization. Many domestic scholars have attempted to render it harmless and utilize it as a resource. Gao Weidan et al. used agricultural byproduct sodium sulfate waste as raw material, adding calcium acetate solution to prepare a high-performance gel material-α-hemihydrate gypsum; they also proposed a method for preparing anhydrous sodium sulfite from industrial byproduct anhydrous sodium sulfate; Wu et al.'s research found that sulfate wastewater can promote the formation of gel structures and can be used to replace tap water in cement production.
Using sodium sulfate to produce soda ash is also an important way to treat industrial byproduct sodium sulfate. The principle of this method is: sodium sulfate reacts with ammonium bicarbonate in a metathesis reaction to obtain sodium bicarbonate with low solubility. Sodium bicarbonate easily decomposes into sodium carbonate, water, and carbon dioxide at high temperatures, and high-purity sodium carbonate is obtained after high-temperature calcination. The mother liquor produced during alkali production contains a large amount of NH4+ and SO4-. These can be crystallized out by evaporation and concentration to obtain ammonium sulfate crystals. This method consumes ammonium bicarbonate to recover sodium sulfate as a resource. The produced sodium carbonate can be used in glass manufacturing, household detergents, and food processing, while ammonium sulfate is mainly used as fertilizer and is suitable for various soils and crops.
