Study On Leaching Characteristics Of Heavy Metals In Copper Tailings Resource Products From A Mining Area In Tibet

With the development of society and industry,the demand for mineral resources in my country has gradually increased,and large-scale mining has led to the accumulation of tailings.In solving the problem of large-scale accumulation of tailings,the recovery of valuable components of tailings,the production of building materials and other utilization methods have become effective ways of recycling.When tailings resource products are put into use or discarded,heavy metals in tailings may still be released due to differences in the amount of mixing,technology,environment,and use methods.Before the tailings resource products are put into the market,it is particularly important to avoid the secondary pollution caused by heavy metals in the tailings to the environment,and to master the leaching characteristics of heavy metals in the tailings resource products.Therefore,this paper studies the leaching characteristics of heavy metals for two kinds of copper tailings resource utilization products,namely copper tailings improved cultivation soil and copper tailings cementation test block.The improved BCR method was used to extract the occurrence form of heavy metals,and the leaching experiments of heavy metals under different p H and time conditions were carried out.To provide a scientific basis for the leaching of heavy metals from copper tailings resource products in Lhasa area.The research results obtained are as follows:1)The water content of copper tailings is 18.48%,the p H value is8.91,and the tailings density is 2.98 g/cm3.The concentrations of heavy metals in copper tailings were higher than Fe(57540 mg/kg),Mn(1704.2mg/kg),Cu(1370 mg/kg),Pb(1020 mg/kg)and Zn(832 mg/kg).Among them,the bioavailable states of Cu,Pb and Zn account for more than 50%,which are relatively active and have large potential migration ability.2)In the copper tailings cultivation soil,in terms of the occurrence form of heavy metals,the weak acid extraction state accounts for the largest proportion of Cd,the reducible state accounts for the largest proportion of Pb,and the oxidizable state accounts for the largest proportion of Cu.The bioavailable states show strong potential migration capabilities of Cu,Pb,Zn,and Cd.When the p H of the leaching solution is 3-4.5,the maximum leaching amount of heavy metals occurs within 8 hours;with the increase of the p H of the leaching solution to 7-8.56,the maximum leaching amount of heavy metals is concentrated in 10-16 hours.Compared with the environmental quality standard of surface water(GB3838-2002),the leaching results of sulfuric acid and nitric acid method(HJ/T299-2007)showed that the leaching amount of As in the cultivated soil was higher than the limit of the quality standard of class V surface water.3)The kinetic fitting result of the leaching curve of heavy metals in the improved cultivation soil of copper tailings is that the leaching of most heavy metals is in line with the second-order kinetics.It shows that the release of heavy metals in cultivated soil is a complex process controlled by multiple mechanisms4)In terms of the distribution of heavy metals in the copper tailings cementation test block,the weak acid extraction state accounts for the largest proportion of Cd(46.85%),the reducible state accounts for the largest proportion of Pb(58.68%),and the oxidizable state accounts for the largest proportion of As(64.23%).The results of the proportion of bioavailable states showed that Cd,Pb,As and Zn have larger potential migration capacity.The sulfuric acid nitric acid leaching experiment and effective amount leaching results of the copper tailings cemented test block show that the leaching amount of As and Cu in the test block is relatively large.And the heavy metal leaching concentration of sulfuric acid nitric acid method is higher than the effective amount leaching.Compared with the "Surface Water Environmental Quality Standard",the leaching concentration of As is higher than the Grade V surface water quality standard.5)The continuous water tank leaching results of the copper tailings cementation test block showed that the leaching amount of Cd,Cu,Cr and As was about 20 days,which basically reached the equilibrium state.The release mechanism of Fe,Cd,Cu,Cr and As in the gelled test block is mainly surface scour,and Zn is mainly dissolved.The mobility rates show that Cu is medium mobility and As is high mobility.Cr and Cd have moderate to high migration rates.