Research on process of preparing sodium fluoride from waste liquid containing fluorine as resource
The shortage of fluorite resources leads to the shortage of fluorine resources.In order to relieve the pressure of fluorine resources,it is necessary to fully improve the effective utilization rate of fluorine resources.The free fluorine in the waste liquid containing fluorine was recycled to prepare sodium fluoride by precipitation method with ammonium fluoride or hydrofluoric acid waste water as raw materials.The effects of reaction time,temperature,pH,and sodium salts on the quality of sodium fluoride products during the preparation process were studied,and the reuse frequency and effect of the filtrate af-ter the reaction were explored.The results showed that when the reaction time of ammonium fluoride waste liquid was 120 min,the reaction temperature was 85℃ and the molar ratio of fluoride ions to sodium ions in sodium chloride was 1∶1,the quality of prepared sodium fluoride was best(98.30％)and the yield was 67.92％.After the reaction,the filtrate was evaporated after defluorination,and the nitrogen content of ammonium chloride reached 24.47％,which was met the require-ments of agricultural ammonium chloride qualified products.The pH of the waste liquid containing hydrofluoric acid was ad-justed to 6 by neutralization and sodium hydroxide.The mass fraction of sodium fluoride was 98.15％,and the filtrate could be reused at least 5 times.The process of preparing sodium fluoride from waste liquid containing fluorine with different com-ponents was realized in this work,which greatly reduced the waste of fluorine resources and made the fluorine resources fully and effectively utilized.
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