Separation of arsenic from lead smelter ash by acid leaching combined with pressure oxidation

Smelter ash contains appreciable valuable metals and a large amount of arsenic due to its volatilization. The safe treatment of smelter ash with high arsenic is of great importance both for environmental protection and resource comprehensive utilization. In the present study, an acid leaching process combined with pressure oxidation was used to separate arsenic from lead smelter ash. In the acid leaching process, the effects of acid concentration, partial oxygen pressure, temperature, liquid-to-solid ratio, leaching time, and agitating speed were investigated, and the optimized leaching conditions were established: 100 g/L of H2SO4 concentration, 2.5 h of leaching time, 170 degrees C of temperature, 10 mL/g of liquid-to-solid ratio, 500r/min of agitating speed and 2.5 MPa of partial oxygen pressure. Under these conditions, the extractions of As, Cd, In, Zn, and Sb were 98.19%, 98.98%, 91.72%, 95.32%, and 24.23% respectively. 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 2.38 kJ/mol.