Study On Mechanism And Technology Of The Comprehensive Recovery Of Copper,Iron,Lead,Zinc And Antimony From Lead Slag

Lead slag is a kind of solid waste discharged from lead smelting processes and other lead-containing smelting slag.Toxic heavy metals in open-air stockpiling?e.g.,Pb,Cr,and Cd?,are easily released into soil and groundwater by rain,wind and are difficult to decompose.Consequently,environments become chronically and irreversibly polluted.Lead slag always contains a certain amount of valuable metals,such as Ag,Fe,Pb,Zn,and In.And the recovery of valuable metals from lead slag relieves the shortage of non-ferrous resources and minimizes their adverse effects on environment.Most previous studies have focused on extracting Pb,Zn,and other volatile metals by pyrogenic process,as well as the easy leaching elements in lead slag by hydrometallurgy.These studies all have reference meaning to recovery valuable metals from lead slag.However,studies on the comprehensive recovery of Cu,Fe,Pb,Zn,and Sb are few.In this study,the blast furnace lead slag was obtained from a lead smelter in Guangxi province.Coal-based direct reduction-magnetic separation-chemical separation process was used to recover Cu,Fe,Pb,Zn,and Sb,this process provided technological basis and theoretical guidance for the industrial application of lead slag.In direct reduction,Pb and Zn compounds were reduced to elementary substances and entered into flue gas as dust.Fe was reduced into metallic iron and separated from roasted slag by magnetic separation.Moreover,Cu and Sb remained in roasted slag,which were recycled by chemical separation.Results reveal that pre-processing of lead slag by coal-based direct reduction was effective.Under optimal conditions,such as lignite ratio of 40%,CaO ratio of 10%,roasting at 1250 ? for 60 min,first-stage grinding fineness-74?m ratio of 65.76%,and second-stage grinding fineness-45?m ratio of 54.27%,and magnetic field intensity of two-stage magnetic separation of 159.24 kA/m and 63.69 kA/m,a magnetic concentrate containing 91.13%total iron was obtained at a recovery rate of 87.36%.The Cu and Sb can be separated by oxidization-acid leaching.Under the best leaching conditions,91.58%of Cu and 86.07%of Sb in magnetic separation tailings were leached into lixivium.Under the optimum reaction conditions,10.35%of Sb products were obtained by hydrolysis reaction at a recovery rate of 64.84%.By adding Na2S into the filtrate,copper sulfide product with 36.92%Cu was then obtained at a recovery rate of 63.73%.In the volatilization dust,98.18%of Zn was leached out.Zn carbonate precipitation rate can reach up to 98.65%.Zinc Oxide with Zn grade of 65.14%was obtained by roasting at a recovery rate of 92.75%.Under the optimum reaction conditions,lead carbonate was obtained by adding NH₄HCO₃ and NH₃ H₂O into the zinc leaching slag.Finally,lead oxide with Pb grade of 78.87%was also obtained by roasting at a recovery rate of 84.90%.The technological process with optimum conditions for the comprehensive recovery of valuable metals from lead slag was achieved by integrating various technologies.The mechanisms of phase transformation and valuable metal distribution after direct reduction were studied by X-ray diffraction?XRD?and scanning electron microscope?SEM?,which provide technological basis and theoretical guidance for the industrial application of lead slag.In addition,the results show that the volatilization rate of Pb total lower than that of Zn by the reason of Pb are easily form Fe-Pb,Cu-Pb,and Pb-Sb alloy with Fe,Cu,and Sb in the direct reduction process,moreover Pb can form Ca₂PbO₄ with Ca in in roasted slag as roasting time went on.