| 摘要 |
FIELD: chemistry.SUBSTANCE: invention can be used in inorganic chemistry. Sodium fluoride can be obtained from a by-product of producing wet-process phosphoric acid - hydrofluorosilicic acid, containing silicon dioxide. The method of producing sodium fluoride involves reacting hydrofluorosilicic acid with sodium hydroxide in an aqueous medium at temperature of 80-90°C, mixing to obtain a suspension, separating the sodium fluoride precipitate and washing said precipitate. The precipitate is washed with 6-10% sodium carbonate or hydroxide solution at temperature of 20-50°C. The amount of sodium hydroxide required to break down hydrofluorosilicic acid and convert silicon dioxide to sodium silicate is calculated using the formula m=2.22·m+1.33·m, where mis the mass of hydrofluorosilicic acid per 100% HSiF, mis the mass of silicon dioxide in the starting acid.EFFECT: invention improves filtration properties of the sodium fluoride precipitate and reduces loss of sodium fluoride at the washing step.2 tbl, 2 ex |
