Research On Vacuum Removal Of Arsenic From Copper Dust Containing Arsenic

Arsenic-containing copper dust is a kind of solid hazardous waste produced in the process of pyrometallurgical copper smelting.Its composition is complex and contains a certain amount of lead,zinc,bismuth,copper,tin and other valuable metals.Its harmless and resourceful treatment has become one of the important problems urgently needed to be solved in copper smelting industry.Arsenic-containing copper dust is divided into smelting copper dust and blowing copper dust because it comes from different processes of copper smelting.The smelting copper dust differs greatly in the arsenic content and arsenic occurrence due to the different copper grade and smelting process.The paper firstly used chemical analysis,X-ray diffraction,Electron probe and other various analytical methods to study the occurrence characteristics of main elements in arsenic-containing copper dust.The results show that the arsenic-containing copper dust is mainly composed of PbSO₄?ZnSO₄?H₂O??Zn?H₂O??OH??AsO₃??As₂O₃?Bi₂O₃?SnO₂ and Fe₂O₃.The element arsenic mainly exists in the form of arsenate and arsenic oxide,of which As⁵⁺:As³⁺is 3:1?4:1.Then,for the occurrence characteristics of elements in arsenic-containing copper dust,the technical route of vacuum carbothermal reduction arsenic removal-sulfide roasting deep arsenic removal was put forward,and the occurrence characteristics and evolution rules of elements were studied around this technical route.The experimental results of arsenic removal from arsenic-containing copper dust by vacuum carbothermal reduction show that the arsenic removal rate was 70.14%under the conditions of reaction temperature of 700?,carbon content of 10%,holding time of 5 hours and 10Pa and the yield of valuable metals Pb,Cu,Bi,and Sn is greater than 99%at 650?;the main phases of the residues are ZnS,ZnO,Zn₂SiO₄,Zn₂SnO₄,Pb₇Bi₃,among which arsenic existed in the form of metal arsenide such as FeAs and Cu₃As;arsenic trioxide will preferentially volatilize during the experiment,and arsenic trioxide crystal and powder will be condensed at 120?300?,during the process,some arsenic trioxide is reduced by carbon and converted into arsenic,arsenic vapor is condensed at 350?450?,which is a silver gray elemental arsenic block.The results of deep arsenic removal by sulfurizaton roasting of residue from vacuum carbothermal reduction experiment show that the total arsenic removal rate is 95.33% under the conditions of reaction temperature of 600?,sulfur content of 20%,holding time of 2 hours;the main phases of arsenic removal residue are ZnS?ZnO?Zn₂SiO₄?ZnFe₂O₄?Bi?SnO₂?PbS and Pb₇Bi₃,most of the metal arsenides in the residue react with sulfur to form arsenic;the arsenic content of residue is less than 1.5%,a small amount of Cu₃As exists,and arsenic is mainly collected by condension in the form of As₂O₃.The technical route of vacuum carbothermal reduction arsenic removal-sulfide roasting deep arsenic removal is feasible to deal with the complex arsenic-containing copper dust.The arsenic removal rate can reach more than 95%,and the arsenic content in the arsenic removal residue can be reduced to less than 1.5%;it is rich in valuable metals such as lead,zinc,antimony and copper,which can be directly returned to the furnace for smelting and recovery.There is no waste residue and waste water in the experiment,the waste gas produced is free of arsenic,lead,zinc,copper,bismuth,tin and other valuable metal elements and the comprehensive recovery of valuable metals is more than 99%.