Enrichment Of Waste Sulfur And Mercury Extraction Hydrometallurgy

Great changes have taken place in domestic zinc smelting industry in recent years, zinc oxygen pressure leaching process has gradually been widely adopted. The recovery of elemental sulfur from oxygen pressure leaching residue was carried out by flotation and hot filtration method in a domestic zinc smelter. Although high quality sulfur can be obtained by this method, sulfur recovery is unsatisfactory, and hot filtration residue still contains50%elemental sulfur so that valuable metals in residue cann’t be further recycled. In addition, the ore used in the smelter contains high levels of mercury. After recycling elemental sulfur, the degree of mercury enrichment in sulfide filter cake is not remarkable, which makes it hard for mercury to dispose or utilize.Aiming at the problem of disposal technics to mercury-containing sulfur residue in the smelter, the recovery of elemental sulfur and the separation and enrichment of mercury from flotation sulfur concentrate and sulfide filter cake were studied respectively by sodium sulfide method and ammonium sulfide method, meanwhile, the leaching behaviour of zinc and silver were also studied in the leaching process. A environmentally friendly sulfur recovery process of simple operation and industrial prospect was discussed, furthermore, mecury and other valuable metals could enrich well in the leaching residue to create the favorable conditions for the recovery of valuable metals and to achieve the goal of comprehensive utilization of resources.The results show that the leaching rate of elemental sulfur can reach over98%, the recovery rate is97.65%and the purity of sulfur is99.75%when flotation sulfur concentrate is treated by Na2S leaching and CO2precipitating method. However, the elemental sulfur depositing from leaching solution by this process, H2S gas escapes from the tail gas to cause some environmental pollution problems. What is more, consumption of various reagents in the process make the system complex, there are some difficulties on the determination of sodium sulfide concentration in the tail solution, and its recycling needs further study.This paper mainly discussed ammonium sulfide method by which flotation sulfur concentrate and sulfide filter cake were treated This process is simple, easy to control, only consumes the single reagent, and has strong applicability for different sulfur-containing materials. In lab-scale test, the effects of various factors on leaching process and distillation thermal decomposition were studied when flotation sulfur concentrate and sulfide filter cake were treated respectively by ammonium sulfide method. For flotation sulfur concentrate, the leaching rate of elemental sulfur is more than98%, about98%of sulfur is reclaimed, and the purity of sulfur is99.57%. The contents of mercury and zinc are enriched6times or more in the leaching residue which can be reduced by more than84%. For sulfide filter cake, the leaching rate and the recovery rate of elemental sulfur both reach over95%, and the purity of sulfur is99.62%. The enrichment rates of mercury and zinc are more than95%and about99%, respectively. An epuipment production line of pilot test was established on the basis of the lab-scale test. The experiments of Leaching, solid-liquid separation and distillation crystallization of200kg sulfide filter cake were carried out. The results of pilot test are basically the same as that of lab-scale test, and the purity of sulfur product is99.77%, in accord with the GB/T2449-2006industrial first-rate product standard. After recycling elemental sulfur, the average contents of mercury, zinc and silver in the residue are0.40%,34.40%,1691.9g/t, respectively, and the residue can be further processed to realize the comprehensive utilization of resourcesIn conclusion, ammonium sulfide process, with high sulfur recovery rate, can obtain high quality sulfur, and make mercury and other valuable metals enrich well in the leaching residue. Ammonium sulfide can be recycled back into process, with less reagent loss, the efficiency of ammonium sulfide recovery is more than91%in both lab-scale test and pilot test, which greatly reduces the production cost. The process is basically a closed-loop operation, doesn’t cause new pollution to the environment and has wide industrial prospect.