EFFECT OF CERTAIN SURFACTANTS ON THE LEACHING AND PRECIPITATION PROCESSES IN ZINC FERRITE RESIDUE TREATMENT

Abstract

The effect of a surfactant mixture of nonylphenolpolyethylene glycol (D1), dinaphthylmethane-4,4′-disulphonic acid (D2), and polyethylene glycol with molecular weight 400 (D3) on the dissolution of zinc and metal impurities present in zinc ferrite residue in dilute sulfuric acid (160 g L−1 H2SO4) as well as on both jarosite and goethite precipitation was studied at 90°C. The following influences of the surfactant mixture (D1 + D2 + D3), determined by comparing the results obtained in the presence and absence of surfactants, were found. Adsorption of surfactants on zinc ferrite residue surface decreases the dissolution of zinc and metal impurities (Fe, Cu, Cd, As, Sb, and Co). Their extraction efficiencies at the end of the super hot leaching process carried out with surfactants are 4.85–6.29% lower than without them. The formation of a sulfur “sponge” layer on the surface of liquor during the dissolution of ZnS present in zinc ferrite residue is hindered by the surfactants due to their effect as wetting agents and sulfur dispersants. The presence of surfactants reduces the amount of zinc and metal impurities (Fe, Cu, Cd, and As) remaining in the solution after jarosite or goethite precipitation by 5.33–5.86% or 8.03–9.93%, respectively. The volume of jarosite and goethite precipitates increases in the presence of surfactants due to their effect as wetting and flocculation agents. On the other hand, D1 and D3 act as complexing agents. The abovementioned effects of surfactants improve the sorption capacity of both jarosite and goethite, thus ensuring better purification of zinc sulphate solutions, but hindering zinc leaching.