Chromium extraction with organic solvents - Part 3. Application to the treatment of polymetallic industrial residues

The use of Primene 81R as extraction agent of chromium present in solid was tes containing nickel, iron and copper has been studied. The waste was leac hed with a sulphuric acid solution up to pH 3 and oxidation of Cr(III) to C r(VI) with Care acid was also studied. Because of the negative result of ox idation, the treatment was applied on Cr(III) directly. Extraction/scrubbin g/stripping process was studied in the leach. The composition of organic ph ase used in the extraction step was 10 % v/v Primene 81R, 10 % isodecanol a nd kerosene. All the iron, 91 % Cr, 10 % Ni and large parr of the copper co ntained in the initial leach solution are recovered in the organic phase. I n the scrubbing stage (with a sulphuric acid solution at pH 1,4), all the c opper and nickel and 30 % Cr go to the washing liquor, while all the iron a nd 70 % Cr remained in the organic phase. In the stripping stage (with a 2N NH4OH or 2N NaOH solution) all the iron and chromium an recovered as a pre cipitate of highly absorbent hydroxides. After the treatment mentioned, 63 % Cr and 100 % Fe are recovered as a mixture of hydroxides, and 28 % of the initial chromium, all the nickel and the copper are found in the washing l iquor.