Beyond dumping: New strategies in the separation of preservative salt from tannery waste mixed salt and its reuse for tannery industrial application

The tannery effluent treatment plants produce tonnes of waste in the form of mixed salts containing sodium chloride, sulfate, calcium, and magnesium salts. Disposal of these mixed salts may create an environmental problem. The proposed method broadly consists of the separation of sodium chloride from reverse osmosis (RO) reject and raw-hide waste salt (preservative salt) of the tannery. This study used the physicochemical method to treat waste salt from tannery industrial waste. The addition of sodium hydroxide and sodium carbonate improved calcium and magnesium removal efficiency in the RO reject and preservative waste salts. The optimization of the sodium salt of hydroxide and carbonate is very important to remove an unwanted substance from waste salt. The sodium chloride was recovered, and the purity was about >98% which was successfully reused as preservative salt as well as in the pickling process in the tannery industry.