Oxygen pressure leaching of arsenic and antimony bearing flue dust in NaOH solution

The oxygen pressure leaching of arsenic and antimony bearing flue dust in NaOH solution was investigated and the effects of NaOH concentrate, O2 pressure, temperature, time and mass ratio of liquid to solid were evaluated experimentally. The results show that the main phases of arsenic and antimony in the flue dust produced in the pyrometallurgical treatment of anode slime of lead electrorefining are As2O3 and Sb2O3 separately, with a small amount of antimony also being in the form of Sb2O5. In the process of the oxygen pressure leaching of arsenic and antimony bearing flue dust in NaOH solution, As(III) ions are oxidized into As(V) with a higher dissolubility in alkaline solution in the leaching process, while Sb(III) ions are also oxidized into Sb(V) and precipitated into leach residue in the form of Sb2O3·2Sb2O5, Pb2Sb2O7 and NaSb(OH)6. The optimum condition of the leaching is determined to be as follows: NaOH concentrate of 40 g/L, O2 partial pressure of 2.0 MPa, temperature of 140°C, leaching time of 2 h, the mass ratio of liquid to solid of 10. Under the optimum conditions, the leaching rate of arsenic is more than 95%, while both of the leaching rates of antimony and lead are less than 1.0%, correspondingly.