Study On Pressure Leaching Of Copper And Simultaneous Arsenic Fixation From Hydrometallurgical Zinc-copper-arsenic Sla

During the roasting process of conventional zinc hydrometallurgy,copper forms copper ferrite and copper silicate with iron and silicon,which enter the zinc leaching slag.Some arsenic forms arsenate with alkaline metal oxides,which also enters the zinc leaching slag,The reductive leaching solution of zinc leaching residue from zinc hydrometallurgy uses the metallic iron replacement method to produce an copper arsenic precipitation.The copper arsenic precipitation from zinc hydrometallurgy contains valuable metal elements such as copper,zinc,and iron,as well as harmful elements such as arsenic.The main phases are Cu₃As and Cu₂O,The content of metal copper reaches more than 50%,and the content of arsenic reaches 15%,Recovering copper from copper arsenic precipitation has high economic benefits.Taking the copper arsenic precipitation from zinc hydrometallurgy as the research object,Copper was leached into the solution using a pressure leaching method,and arsenic was stabilized and solidified in the form of odorite,achieving efficient separation of copper and arsenic.The process parameters and behavior of copper and arsenic during pressure leaching of copper and arsenic residue were emphatically studied.The main research contents and conclusions are as follows:（1）Thermodynamic analysis of pressure leaching of copper arsenic precipitation and thermodynamics study of arsenic sinking in scorodite.Cu₃As dissolution reaction in the oxidation dissolution process of copper arsenic precipitationΔG compared to Cu₂O dissolution reactionΔG is more negative,and Cu₃As is first leached into the solution during the oxidation leaching stage;The thermodynamic theoretical stability regions of copper arsenate and iron arsenate at 135℃are 0.65<p H<8 5.When-0.25<p H<0.65,there is no copper arsenate phase in the Cu-Fe-As-H₂O system.Controlling the p H value of the reaction within this range can achieve the separation of copper and arsenic.（2）The effects of reaction temperature,reaction time,sulfuric acid concentration,molar ratio of iron to arsenic,liquid-solid ratio,and oxygen partial pressure on the separation of copper and arsenic were studied.When the reaction temperature is below135℃,the leaching rate of arsenic is above 90%.Increasing the reaction temperature decreases the leaching rate of arsenic,which is conducive to the separation of copper and arsenic.The arsenic leaching rate decreases and the arsenic content in the leaching residue increases with the prolongation of reaction time.When the concentration of sulfuric acid increases,the leaching rate of copper and arsenic both increase,and high acidity is not conducive to the synthesis of odorite from arsenic and iron.Increasing the molar ratio of iron to arsenic decreases the concentration of arsenic in the leaching solution,which is beneficial to the separation of copper and arsenic.Increasing the liquid-solid volume to mass ratio is not conducive to the synthesis of arsenic and iron,making it difficult to synthesize allite.Increasing the oxygen partial pressure of the reaction system is beneficial to the precipitation of arsenic,resulting in a better crystal form and high stability of odorite.Under the optimized technical conditions,the leaching rate of copper and arsenic are 98.74%and 4.73%respectively,the arsenic content in the leaching residue is 26.29%,the copper content is 1.52%,the arsenic concentration in the leaching solution is 0.59 g/L,and the copper concentration is 20.00g/L,The mass ratio of copper to arsenic in slag decreased from 3.60 to 0.58,achieving efficient separation of copper and arsenic.（3）Research on the behavior of copper and arsenic in the process of pressure leaching copper and solidification arsenic precipitation.At the initial stage of the reaction,copper leaching and arsenic precipitation are conducted simultaneously,and the variation trend of the p H value of the leaching solution and the concentration of As in the leaching solution is basically consistent.At the early stage of the reaction,the acid generated by the formation of allite from arsenic and iron can supplement the acid consumed by copper leaching,maintain a low acid environment required for precipitation reaction.In the initial stage,the dissolution reaction of copper and arsenic is mainly carried out,while in the later stage,the reaction mainly involves the synthesis of odorite from iron and arsenic.The odorite formed by arsenic and iron begins to aggregate from some irregular small particles,and then the odorite particles gradually take on a certain geometric shape.Later,the odorite particles become plump and have obvious surface patterns.