Objective:To precipitate the fluoride ions in the fluorine-containing waste salts generated during the synthesis of fluoroethylene carbonate by precipitation-flocculation method,and to recover the by-product potassium chloride.Methods:The optimal defluoridation process was determined by investigating the types,dosages and pH of precipitants,flocculants,etc.,and the optimal recovery conditions of potassium chloride were determined by exploring the crystallization temperature and washing water consumption of potassium chloride.Results:When CaCl2 and Ca(OH)2 were selected as precipitants,pH was 8.0 and n(Ca2+)∶n(F-)was 0.7,the fluoride ion concentration in the solution was reduced from 153 mg/L to 20.3 mg/L by using the single-stage fluoride removal process.Conclusion:When n(Al3+)∶n(F-)is 12∶1,the residual fluoride ion concentration is reduced from 20.3 mg/L to 3.0 mg/L,and the purity of potassium chloride is as high as 99.7%,which meets the national discharge standards for industrial wastewater,and the overall process reflects the requirements of green and economic chemistry.
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