Method for preparing ammonium fluoride from tertiary amine-fluosilicate

The invention relates to a method for preparing ammonium fluoride from tertiary amine-fluosilicate. The method includes the process steps that firstly, tertiary amine is added into diluted fluosilicic acid to serve as an extraction agent, a tertiary amine-fluosilicate solution and an aqueous phase which cannot be dissolved in water are obtained after extraction layering, and the aqueous phase returns to a phosphorite decomposed tail gas absorbing system to absorb silicon tetrafluoride; secondly, ammonia gas is introduced into the tertiary amine-fluosilicate solution in the first step and stirred, and then an ammonium fluoride and silicon dioxide mixture filter cake and tertiary amine filtrate are obtained through filtration; thirdly, the tertiary amine filtrate obtained through filtering in the second step is returned to the first step to extract the diluted fluosilicic acid; fourthly, an ammonium fluoride saturated aqueous solution is prepared at the temperature of 0 DEG C, an ammonium fluoride and silicon dioxide mixture obtained after being heated is added into the solution, and a supersaturated ammonium fluoride solution and silicon dioxide are obtained respectively through stirring, washing, heat preserving and filtering; fifthly, the silicon dioxide is washed and dried, and white carbon black is obtained; sixthly, the supersaturated ammonium fluoride solution is cooled below the temperature of 0 DEG C, and ammonium fluoride mother liquor is heated and then recycled.