A Study On Comprehensive Utilization Of The Cinder In Arsenite Preparation

Containing higher contents of Fe, S and As, as well as some minerals of Zn, Pb and Ag, the cinder in arsenite preparation is a valuable residue. In conventional technique of producing arsenite, however, this cinder was disposed by burying on the spot or stockpiling, resulting in a serious environmental pollution and a waste of valuable minerals.Based on a great deal of researches for recovery of S, Fe and Zn from solid waste, a comprehensive utilization technique, including oxidation roasting-absorption with pyrolusite pulp, deoxidization roasting-magnetic separation and acid leaching, was investigated in this paper.Test results showed that (1) Arsenic was transformed into arsenate compounds after a high temperature roasting, and precipitated. (2) The flue gas generated in the process of oxidation roasting was absorbed by a lower pyrolusite pulp, and sulfur was recovered. The optimum condition of oxidation roasting was roasting temperature 650℃, roasting time 60min, and the cinder fineness was less than 97μm. Two troughs of absorption were used to improve the leaching rate of Mn and the desulfurization rate. (3)Fe in the arsenic cinder was recovered by deoxidization roasting-magnetic separation after desulfurization. The optimum condition of deoxidization roasting was roasting temperature 550℃, roasting time 30min and less than 97μm of the cinder fineness. At a certain magnetic intensity, the recovery of Fe was up to 84.86%. (4) Zinc was recovered by acid leaching under high temperature after the cinder was treated by oxidation roasting and subsequent deoxidization roasting. The optimum condition of acid leaching was as following: leaching temperature 90℃, 20% of the mass fraction of sulfuric acid , 5:1 of the L/S and 120min of the leaching time.On the base of conditional tests, a flow-sheet for recovery of Fe, S and Zn was developed. In this flow-sheet, S was recovered in the form of manganese sulfate, Fe and Zn was separated from the cinder with a recovery of 86.83% and 83.43% respectively. The grade of Ag in the final residue was 246g/t.