METHOD OF PRODUCING SODIUM FLUORIDE Russian patent published in 2014 - IPC C01D3/02 

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_NaOH=2.22·m_H2SiF6+1.33·m_SiO2, where m_H2SiF6 is the mass of hydrofluorosilicic acid per 100% H₂SiF₆, m_SiO2 is 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.

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