It is mainly used as a stabilizer for synthetic fibers, a bleaching agent for fabrics, a photographic developer, a deoxidizer for dyeing and bleaching, a reducing agent for fragrances and dyes, and a lignin removal agent in papermaking.
In water treatment, sodium sulfite is used as a deoxidizer for boiler water and oilfield injection water, and a dechlorinator for municipal or industrial water. In wastewater treatment, it is used to reduce hexavalent chromium salts to low-toxicity trivalent chromium salts, and can precipitate and separate silver and mercury from wastewater. Sulfite is widely used in small and medium-sized boilers and boilers operating at pressures below 5.88 MPa, typically prepared as a 2%–10% solution. The usual dosage of sodium sulfite is 0.076 g/L. It is best to add an appropriate amount of catalyst, such as salts of Cu, Co, Mn, and Ni, to improve the deoxygenation rate. When a boiler is not in use, it can be filled with alkaline deoxygenated water containing approximately 200 mg/L sodium sulfite to protect the metal from corrosion. When removing excess free chlorine from water, sodium sulfite should be used in combination with sodium bisulfite or sulfur dioxide. Additionally, as a deoxidizer for water injection in oilfield production, adding just 10 mg/L of sodium sulfite can control dissolved oxygen corrosion of well casings. Furthermore, sodium sulfite is used in chemical production as a raw material for sodium thiosulfate production, and is also a stabilizer for viscose fibers, a disinfectant for beer bottles, an engraving agent for glass mirrors and slates, a bleaching component and deoxidizer for fabrics, and a developer for the photosensitive industry.
