| 摘要 |
Metal ion impurities are removed from phosphoric acid by adding to the acid a precipitant comprising ions Or calcium and fluorine to cause precipitation Or, for example, a magnesium-containing precipitate. A preferred precipitant is one containing calcium fluoride, such as the sludge obtained by treating pond water from a phosphoric acid plant with a calcium-containing compound. Preferably, the soluble sulphate content of the phosphoric acid is maintained at at least about 2 by weight. An animal feed can be prepared from the precipitate by combining the precipitate with phosphate rock, water, and a sodium-containing compound, and then calcining the combination. |
