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Interfacial studies in the zinc pressure leach technology Owusu, George


Interfacial tension measurements in the liquid sulphur - zinc sulphate solution system, and contact angle measurements in the liquid sulphur, aqueous solution and zinc sulphide mineral were made at a temperature of 125 ± 4°C under superatmospheric conditions using the pendant drop technique. The purpose of these measurements was to study the dramatic effect of surface active agents, particularly ligninsulphonate on the performance of the zinc pressure leach. The measurements obtained showed that, in the absence of surfactant, the liquid sulphur - aqueous solution interfacial tension was 54±1 dynes/cm and this value was reduced to 27-30 dynes/cm when 0.3g/l ligninsulphonate was present in the system. The contact angle obtained was 80±5° in surfactant-free system. This value increased to 148 ± 5° when 0.3g/l ligninsulphonate was present in the system. The reduction in the interfacial tensions, combined with the mechanical agitation of the slurry disperses the liquid sulphur into small droplets in the slurry and the increase in contact angles reduces the liquid sulphur - solid mineral adhesive work from 63.7 ergs/cm² in the surfactant-free system to about 5.3 ergs/cm² in the presence of 0.3g/l ligninsulphonate. These properties enhance sulphur removal from the surface of any unreacted zinc sulphide mineral in the zinc pressure leach technology. These results indicate that the surfactant is adsorbed at both liquid sulphur - aqueous solution and aqueous solution - marmatite mineral interfaces.

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