| 摘要 |
A method of removing heavy metals, particularly cadmium, from wet-process phosphoric acid produced by digesting raw phosphoric material with sulphuric acid, by precipitating out the heavy metals in sulphide form. The residual sulphuric acid is removed first by neutralization with alkali or as a not-readily dissolved sulphate precipitate. Alkali is added to obtain an Me/P ratio within the range of about 0.05-0.3, where Me is the number of catio equivalents in the alkali and P is the number of phosphorous atoms in the phosphoric acid, whereafter the heavy metals are precipitated out by adding a sulphide compound which is soluble in the phosphoric acid, and the sulphide precipitate removed. |
