The treated sodium fluoride raw material contains many sodium silicate impurities.In order to remove the impuri-ties in it,improve the purity of sodium fluoride and obtain higher industrial value,using silicon dioxide generation with evaporation crystallization,a process of sodium fluoride purification by silicon dioxide generation-evaporation crystallization was designed to improve the purity of sodium fluoride,reduce the content of silicon,and improve the appearance of the so-dium fluoride product.In the silicon dioxide generation experiment,the effects of sulfuric acid dosage ratio,temperature,time and stirring speed on the desilication process were investigated,and orthogonal experiments were carried out.The re-sults showed that in the silicon dioxide generation experiment,the desilication conditions with the best overall performance were:sulfuric acid dosage ratio of 0.04,reaction temperature of 25℃,reaction time of 30 min,and stirring speed of 300 r/min.In the evaporation and crystallization experiment,the best overall performance of evaporation and crystallization for the puri-fication of sodium fluoride was achieved when the evaporation time was 60 min.Under the optimal experimental conditions,a sodium fluoride product with a purity＞98%and a silica mass fraction＜0.5%could be obtained.The study showed that the reaction between sulfuric acid and sodium silicate could react to produce silica gel,and then filtration and separation could achieve the effect of silica removal,and the purity of sodium fluoride could be further improved by evaporation and crystalli-zation.This study could provide new ideas for the purification of sodium fluoride and the recovery of fluorosilicon resources.
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