Arsenic removal from lead-zinc smelter ash by NaOH-H2O2 leaching

The safe treatment of smelter ash with high arsenic is of great importance both for environmental protection and resource comprehensive utilization. In this study, arsenic removal from lead-zinc smelter ash by NaOH-H2O2 leaching was studied. The effects of different operating parameters on the leaching rate of arsenic and leaching kinetics were investigated based on thermodynamic calculation. The results indicate that NaOH concentration and H2O2 addition have significant effects on the leaching rate of arsenic. The optimum conditions were established as: liquid-solid ratio, 10:1; NaOH concentration, 3 mol/L; H2O2 concentration, 2.4%; leaching time, 2 h; and leaching temperature, 75 °C. Under these conditions, the leaching rate of arsenic was as high as 98.17%. The kinetic study reveals that the arsenic leaching process is in accordance with the diffusion-controlled type in the Avrami model, and the apparent activation energy is 16.03 kJ/mol.