Method of purifying phosphoric acid of heavy metals
AssigneeBoliden Aktiebolag
InventorHans A. L. Berglund
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Abstract
The present invention relates to a process for removing heavy metals, particularly cadmium, from differing qualities of wet-process phosphoric acids. The invention is based on the concept of removing the heavy metals in sulfide form.
Claims10
A method of removing cadmium and other heavy metals from wet-process phosphoric acid produced by digesting raw phosphoric material with sulphuric acid, by precipitating out the heavy metals as sulphides, comprising first removing from the phosphoric acid any residual sulphuric acid present therein by neutralization with alkali, supplying alkali to the phosphoric acid to obtain an Me/P ratio within the range of about 0.05-0.3, where Me is the number of cation equivalents in the alkali and P is the number of phosphorous atoms in the phosphoric acid;
- precipitating out the heavy metals by adding a sulphide compound which is soluble in the phosphoric acid;
- and removing the resultant sulphide precipitate.
A method of removing cadmium and other heavy metals from wet-process phosphoric acid produced by digesting raw phosphoric material with sulphuric acid, by precipitating out the heavy metals as sulphides, comprising first removing from the phosphoric acid any residual sulphuric acid present therein by precipitation as a not-readily dissolved sulphate, supplying alkali to the phosphoric acid to obtain an Me/P ratio within the range of about 0.05-0.3, where Me is the number of cation equivalents in the alkali and P is the number of phosphorous atoms in the phosphoric acid;
- precipitating out the heavy metals by adding a sulphide compound which is soluble in the phosphoric acid;
- and removing the resultant sulphide precipitate.
Dependencies are inferred from the claim text.