Study On The Preparation Of Anhydrous Potassium Fluoride With The Fluoride In The Liquid Phase Of The Wet Process Phosphoric Acid

Potassium fluoride is an important inorganic fluorine chemical product, which is widely applied to medicine,antiseptic and glass sculpture and so on, especially to the synthesis of fluorinated organic products. With the shortage of the traditional fluorite fluorine resources,It’s becoming important to produce potassium fluoride with the fluorine of the wet process phosphoric. The main purpose of this paper is to fully utilize the fluorite in the liquid phase of the wet process phosphoric, defluorination and preparing potassium fluoride. The defluorination and process of making potassium fluoride as well as the related mechanism was studied in this paper.The defluorination process of the potassium sulfate and the potassium chloride were both studied. The best defluorination conditions of the former were as that: the amount of potassium sulfate was 1.2 times as the theoretical, the reaction time was 1h, the reaction temperature is 30℃. The other were that : the amount of potassium chloride was 1 times as the theoretical, the reaction time was 1h, the reaction temperature is 30℃. They were both conducted in a stirring condition of 30 rpm. Simultaneously, the defluorination process of the fluosilicic acid was researched as well, the best conditions was that: the reaction temperature is 30℃, the potassium sulfate and the potassium chloride were 1 times as the theoretical, the reaction time was 1h,the yield of the potassium fluosilicate was about 92%.The defluorination product potassium hexafluorosilicate then was reacted with potassium hydroxide to prepare potassium fluoride, the best conditions were as the follow: the amount of potassium hydroxide was1.07 times as the theoretical, the reaction time was 1h, the reaction temperature 80℃,the concentration of potassium hydroxide solution was 30%~40%,the ratio of potassium fluosilicate to water was1:3, the filter cake washing 3 times, the terminal value of pH was within 7.7~8 when adjusting the pH with fluosilicic acid. The yield of potassium fluoride was about 92%.The quality control of potassium fluoride was on the study. If the terminal value of pH was too high or too low, the free alkali or acid would be excess. When the pH was 7~8,the silica content of products was lower. In the reaction of preparing potassium fluoride, r mH?? 〈0, It is an exothermic reaction and ΔrGm﹤0,It can be carried out spontaneously. There existed an obvious induction time of the reaction, high temperature can shorten the induction time significantly.