Hydrometallurgical extraction of antimony from lead refining slags
Today, in order to optimize the production of copper, zinc, and lead, as well as to reduce the circulation of associated metal impurities (such as antimony, tin, bismuth and others) between the processing facilities, an ever greater attention is given to the development and implementation of processing schemes that would enable to extract associated metals and use them to produce commodities. In connection with the above, a process has been developed and tested for processing lead refining slags which include, %: 25–30 Sb, 2–10 Pb, 1–8 Sn, 3–12 As, 0.1–0.2 Cu. The resultant products included the Su-2, Su-1 and Su-0 grades of antimony or antimonous oxide. It was found that the forms in which antimony was present in the untreated slag included Sb2O3, Sb2O4, Sb2O5 and NaSb(OH)6. A hydrometallurgical process based on the use of sulphide alkaline solutions was taken as the basic slag processing technique. It is proposed to wash the slag additionally before leaching to remove arsenic from antimony, and to use the electrowinning stage to separate tin from antimony. Regimes have been identified for obtaining cathode deposits containing 96–99% Sb, with the recovery of antimony from untreated slag being 67%. The cathode deposits were refined with the help of pyrometallurgical methods and electrolysis in sulphate-fluoride media. The paper also considers the possibility of obtaining antimonous oxide by oxidizing the antimonous oxide melt and recovering Sb2O3 from exhaust gases. Based on the findings and the results of the tests, Uralelectromed is now working on designing a slag processing facility.