RESEARCH AND DEVELOPMENT OF TECHNOLOGY FOR PRODUCTION OF SODIUM FLUORIDE, AMORPHOUS SILICA AND LIQUID GLASS FROM A MIXTURE OF FLUOROSILICIC AND HYDROFLUORIC ACIDS

Abstract

In article presents the results of processing of a mixture of fluorosilicic and hydrofluoric acids – a by-product of fluoride salts and phosphate fertilizers production in order to obtain sodium fluoride, silica gel (amorphous silicon oxide) and liquid glass. On this basis, the optimal technological parameters of the interaction of a mixture of FSA and hydrofluoric acid with sodium hydroxide were determined depending on temperature, process duration and sodium hydroxide concentration. It was found that at temperature 25 ºC, process duration 15 min, sodium hydroxide concentration 45% wt. the degree of sodium fluoride extraction reaches more than 93%. Also, sodium fluoride dissolved during the reaction after hydrolysis of sodium metasilicate with precipitation and filtration of silica gel is returned back to the production cycle for preparation of the required sodium hydroxide solution. It was determined that treatment of amorphous silica forming with 10 % sodium hydroxide solution for 60 min. and temperature 85-90 ºC yields liquid glass. The results of the conducted research are confirmed by chemical and X-ray phase analyses, which gives grounds for the introduction of this technology in the industry. In addition, on the basis of the conducted researches the basic technological scheme of processing of the mixture of FSA and hydrofluoric acid was developed in order to obtain sodium fluoride, amorphous silica and liquid glass.