Process for reducing the heavy metal content, especially of cadmium compounds

摘要

In a process for reducing the heavy metal content, especially of cadmium compounds, of rock phosphate, which is subjected to an acid treatment, the pH in the presence of Ca ions being set to values between 0.2 and 3, particularly according to Patent ... (Patent Application P 3204963.3), a solution is to be provided by which, in the process indicated in the preamble, it is possible to eliminate the heavy metals from rock phosphate in a simple manner. This is achieved in that, after separation of the treated rock phosphate, the heavy metals are precipitated as sulphides by passing hydrogen sulphide into the filtrate containing the heavy metals.