Arsenic and antimony extraction from high arsenic smelter ash with alkaline pressure oxidative leaching followed by Na2S leaching

摘要

In this study, a combined process of alkaline pressure oxidative leaching (APOL) and Na2S leaching was proposed to extract arsenic and antimony from high arsenic smelter ash. The arsenic was selectively dissolved into the leachate during APOL, while the antimony was separated into the residue as insoluble NaSb(OH)(6). The effects of different process parameters on the extraction of arsenic and antimony were investigated based on thermodynamic calculation. The results indicated that the extraction of arsenic was as high as 96% after APOL process under the conditions: 2 mol/L of NaOH concentration, 95 degrees C of leaching temperature, 90 min of leaching time, 1.5 MPa of oxygen partial pressure, 10:1 of liquid-to-solid ratio. The NaSb(OH)(6) generated after APOL could be converted to Na3SbS4 center dot 10H(2)O and thus was leached out by Na2S leaching. The optimum conditions were established as: 2.75 mol/L of Na2S concentration, 95 degrees C of leaching temperature, 120 min of leaching time and 10:1 of liquid-to-solid ratio, under which the extraction of antimony was as high as 97.01%. A series of tests indicated that the leaching toxicity of the leaching residue met the Chinese identification standards.