| 摘要 |
<p>A method for the separate recovery of metals such as chromium, zinc, cadmium and nickel from iron-containing chemical waste, is disclosed. To achieve good separation of these metals from each other and without contamination by lead, and also with effective removal of iron, the method has the following steps: A. treatment of the waste with an acid whereby an aqueous solution (1) and a residue are obtained, B. selective extraction of iron (III) from solution (I) at a pH of 0-1 using an organo-phosphoric acid as an extraction medium (I), C-2 oxidative treatment of the chromium (III) in solution freed from iron at a pH of 2-4 using an oxidising agent, such as sodium hypoclhorite (NaClO), and C-3 selective extraction of the chromium (VI) formed from the solution at a pH of 2.5-4 using a suitable extraction medium (III) and the removal of co-extracted cadmium and zinc from the charged extraction medium (III) by washing with a wash liquor such as a sodium sulphate solution at a pH of 3 before back-extraction of the chromium (VI), zinc, cadmium and nickel can be extracted together from the solution freed from chromium at a pH of 6-7 using a suitable extraction medium (V) and separated by back-extraction of the extraction medium (V) at a pH of less than 5 using an aqueous solution which contains about 5 MoL/1 NaCl, fixing of zinc and cadmium from this solution on a strongly basic anion exchanger followed by subsequent elution of zinc and cadmium with about 0.02 m HCl and water respectively, and extraction of the nickel from the solution which has passed unhindered through the anion exchanger at a pH of 6-7.</p> |
