Stabilization of arsenic in waste slag using FeCl₂ or FeCl₃ stabilizer

摘要

With the aim of stabilizing arsenic pollution in mine tailing, FeCl₂ and FeCl₃ were chosen as stabilizers. The changes in pH, speciation, and leaching concentration of arsenic were analyzed. The stabilization mechanism of the FeCl₂ and FeCl₃ stabilizers towards the removal of arsenic has been discussed based on FTIR spectroscopy and XRD results; the results show that both the FeCl₂ and FeCl₃ stabilizers can reduce the pH of arsenic waste slag, but pose the risk of acidification, especially for FeCl₃. Both stabilizers could reduce the content of acid-soluble arsenic. When the Fe?:?As molar ratio was 1.0 and an FeCl₂ mixed solution at pH = 7 and FeCl₃ mixed solution at pH = 4 and pH = 7 were used, the acid-soluble arsenic was decreased by 96.22%, 93.42%, and 96.22%, respectively. The arsenic leaching concentration <2.5 mg L?1, which meets the minimum requirements for the entrance of safe landfill sites, demonstrates that the FeCl₂ and FeCl₃ stabilizers have good stabilizing effects. The acid-soluble arsenic or reducible arsenic can be converted into residual arsenic by the FeCl₂ stabilizer. Furthermore, acid-soluble arsenic was converted into residual arsenic and oxidized arsenic by the FeCl₃ stabilizer.