| 摘要 |
PURPOSE:To remove efficiently fluorine and phosphoric acid, and to obtain by-products having such a purity as to be industrially reusable, by separating and recovering fluorine and phosphoric acid as calcium fluoride and calcium phosphate from a solution containing fluorine and phosphoric acid. CONSTITUTION:A solution containing fluorine and phosphoric acid is adjusted to 3-6pH, 1.5-3 times as much zinc compound as phosphoric acid by equivalent is added to the solution, and slightly water soluble zinc phosphate is precipitated and separated. Then, 1.5-3 times as much Ca compound as fluorine by equivalent is added to the solution, and slightly water soluble CaF2 is precipitated and separated. The filtrate is adjusted to 6.5-10pH, the residual zinc ion is precipitated as zinc hydroxide, separated and recovered. Or, the separated zinc phosphate is dissolved in a dilute acid, phosphoric acid and an equivalent amount of Ca compound are added to the solution at 2-5pH, calcium phosphate is precipitated, separated, recovered, recovered zinc hydroxide is added to a dilute acidic zinc solution of the filtrate, and circulated as the zinc compound of the first process and used.
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