Study On Occurrence Characteristics And Leaching Toxicity Of Toxic Elements In Valuable Components Of Secondary Leaching Residue

Oxygen pressure zinc leaching is a new wet zinc leaching process,which will produce 40%secondary leaching slag(high sulfur slag).At present,China’s zinc smelting enterprises produce about 600,000 tons of high sulfur slag every year,which contains high sulfur content and valuable elements such as silver,lead and zinc.Therefore,the effective utilization of high sulfur slag can not only recover heavy precious metals,but also prevent its harm to the environment.However,due to the uneven particles and high viscosity of high-sulfur slag,the research on process mineralogy is not in-depth,which makes it difficult to treat and utilize high-sulfur slag.There are some problems,such as low direct yield of elemental sulfur and poor synergistic extraction effect of valuable components.Process mineralogy of high-sulfur slag is the basic research and decisive factor in formulating flotation process.There is little research on the process mineralogy of high-sulfur slag,and there is no theoretical support for the improvement of flotation process,so it is necessary to study the process mineralogy of high-sulfur slag in detail.In this paper,the high-sulfur slag,flotation concentrate and flotation tailings of an enterprise in Inner Mongolia are taken as the research objects,and modern testing and analysis methods such as XRF,polarizing microscope,SEM-EDS,XRD,laser particle size analyzer and automatic mineral analyzer are used to find out the content and micro of elemental sulfur,valuable components(lead,zinc,copper,silver and iron),toxic elements(arsenic,cadmium and mercury)and gangue components in the high-sulfur slag of zinc smelting The leaching toxicity test methods such as TCLP method,sulfuric acid-nitric acid method and horizontal oscillation method were used to investigate the leaching toxicity of high-sulfur slag in different environments,explore the leaching toxicity of high-sulfur slag with different particle sizes,the leaching process of high-sulfur slag and simulate the leaching toxicity of high-sulfur slag in harsh environments.The results are as follows:The particle size range of high sulfur slag is>150 μm,150～75μm,75～45 μm and<45 μm,and the mass fractions are 3.12%,33.92%,10.66%and 52.29%,respectively.According to the particle size distribution,the sulfur content in the high-sulfur slag is 76.24%,87.03%,79.48%and 17.55%in turn.By flotation,elements sulfur,zinc and mercury enter sulfur concentrate,while elements lead,silver and iron enter sulfur tailings.Elements sulfur and zinc are enriched in+45 μm particle size,while elements iron and lead are enriched in<45 μm particle size.Sulfur is the main component of high-sulfur slag,pyrite is the main sulfide,followed by chalcopyrite,sphalerite and galena,hematite is the oxide,and quartz is the main gangue mineral.The proportion of fully dissociated sulfur in the concentrate after flotation is 19.93%,32.4%,and that in the tailings is 0.87%,1.78%.Sulfur in high-sulfur slag is mostly associated with fine pyrite particles,and the proportion of binary association is 68.75%and 80.00%respectively;A small amount of complex syngenetic monomer formed by pyrite,chalcopyrite,sphalerite and gangue minerals exist or are embedded in sulfur.Most of the sulfur in tailings is a complex association of large particles,which is associated with fine pyrite and gangue minerals.The sulfur-containing particles in high-sulfur slag,sulfur concentrate and sulfur tailings are divided into smooth,long and straight and irregular shapes according to their shapes,and their proportions are counted respectively.Through the conclusion of process mineralogy,some guiding suggestions are put forward for flotation process.The results of leaching toxicity showed that TCLP method,sulfuric acid-nitric acid method and horizontal oscillation method have great differences in the leaching content of heavy metals in high-sulfur slag.The leaching amount of heavy metals except Pb in TCLP method is lower than that in nitric acid-sulfuric acid method and horizontal oscillation method,while the leaching amount of heavy metals in sulfuric acid-nitric acid method is higher than that in horizontal oscillation method,but the difference is not significant.Generally,the smaller the particle size,the higher the leaching concentration,while the lower the leaching concentration of zinc.In the leaching process of high-sulfur slag by TCLP method and horizontal oscillation method,mercury and copper reach the maximum leaching value in 4～10 h,and the leaching balance can be reached in 18 hours For other metal elements,the maximum leaching value can be reached within 1～4 h,and the leaching equilibrium can be reached within 18 h.The leaching amount of lead in TCLP method increases with the increase of liquid-solid ratio,while the leaching amount of other elements decreases to the lowest when the liquid-solid ratio is 30:1(or 20:1),and the leaching amount of metal increases sharply to the maximum when the liquidsolid ratio continues to increase to 40:1.The leaching behavior of each metal in horizontal oscillation method is complex,and there is no obvious law with the change of liquid-solid ratio.