| 摘要 |
To remove lead and cadmium from phosphoric acid, alkali metal hydroxide solution and aqueous sulphide solution are simultaneously introduced with a thorough mixing into a phosphoric acid having a P2O5 content of up to 32% by weight, an iron content of up to 0.3% by weight and an alkali/P ratio of up to 0.30. The temperature of the phosphoric acid mixed with alkali metal hydroxide solution and sulphide solution is set to temperatures of from 58 to 72 DEG C with the excess hydrogen sulphide being given off. To complete the sulphide precipitation, the temperature is reduced to below 45 DEG C. Finally, the precipitated sulphides of lead and cadmium are separated off from the phosphoric acid. <IMAGE> |
