Technology Of Upgrading Silver Recovery Of Flotation From Zinc Leaching Residues

The hydrometallurgical zinc slag are most piling in tailings reservoir, silver are always contained in these Tesidues,and the grade of silver range from1OOg/t to600g/t.With the shortage of silver resource and silver demand rising, hydrometallurgy zinc leaching residue as one of silver raw materials, has become one of the selection to make up the gap between silver supply and demand. At present, all countries strongly advocated the two comprehensive utilization of resources, the recovery of silver from zinc leaching residue has important significance either in the reducing environment pollution, alleviate the environmental pressure or to avoid waste of resources. As a result of slag composition is diversity and the occurrence state of silver is complex, the factors that effect silver flotation recovery are very complex. Therefore, this article in view of the occurrence of silver that contained in zinc leaching residue which from Inner Mongolia, aim at how to improve the recovery rate of silver with flotation method.The silver pHase analysis showed that:the high acid leaching residue containing silver284g/t, silver in the zinc leaching residue occurrent complex, there is natural silver, silver sulfide, silver chloride, silver sulfate and the silver contained in silicate, silver iron alum, mainly in the natural silver and silver sulfide based accounting for39.43%, the content of silver chloride and silver sulfate which have larger Ksp is36.62%. Through particle size analysis, the zinc leaching residue size is fine, there are69.37%particle size below0.037mm, more than90%silver is enriched in0.074mm. The zinc leaching residue solution characteristics analysis showed that, the slag is high acid leaching slag, flotation pulp contains large amounts of acid, pH value was2. and the residue contain an excess of polyacrylamide flocculant, this polyacrylamide flocculant bring many difficulties to the silver recovery from zinc leach residue because of the flocculant has non selective to fine minerals particles.In this paper the leaching residue characteristics were investigated by a series of single factor experiment research, mainly consider the effect that activating agent, collector, pH value of pulp, dispersing agent, organic carrier and other factors take on the recovery of silver. The test results show that, the collectors can’t collect anything without any activator. Silver recovery can be significantly improved at the condition of dosage of sodium sulfide is1000g/t and react about10min. Mixed collectors can obtain better flotation index than single collector, butyl aerofloat and ethionine urethane mixed at the ratio of7:1. Add dispersant Six partial sodium pHospHate in the flotation tank can reduce the effect that flocculant polyacrylamide take on silver flotation, optimum dosage of Six partial sodium phosphate is120g/t. flotation result would get worse when there are too much six partial sodium phosphate. We can’t get ideal index in the use of conventional flotation technology, use carrier flotation can solve the problems taken by small particle size, when the carrier dosage is3000g/t, the silver index can be significantly improved.At the end, we get ideal silver flotation index under the two closed circuit process, which are at the nature pH values and pH4-4.5. Through the comparison of closed circuit test results, we can get stable flotation index at the pH4-4.5with once rough, once concentration, twice scavenging and middling concentration returned to the last stage. Finally, the silver concentrate grade is8670g/t and the recovery reached62.57%.