Study On The Pressure Deep Leaching And Simultaneous Arsenic Precipitation Behavior Of Copper Smelting Dus

Copper smelting dust is a high value-added secondary resource generated during the process of pyrometallurgical copper refining,which is rich in various valuable metal elements such as zinc,copper,lead,silver,and bismuth.This article proposes a new technology for pressure deep leaching and simultaneous arsenic precipitation of copper smelting dust in response to common technical problems in the industry,such as low leaching rate of valuable metals,dispersion of arsenic,and severe pollution of zinc and copper products in the conventional acid leaching process.By utilizing the unique technical advantages of pressure hydrometallurgy,this new process achieves efficient leaching of zinc and copper from copper smelting dust,simultaneous precipitation of arsenic,and efficient enrichment of lead,silver,bismuth,and other elements.This article systematically studied the influence of process technical parameters on valuable metal deep leaching behavior,arsenic-iron co-precipitation behavior,and phase transformation of leach residues,and carried out large-scale experimental research.The main conclusions are as follows:（1）The chemical composition and phase composition of the copper smelting dust have been determined.The target element contents are as follows:Zn 5.0%,Cu 8.7%,Pb 13.0%,Ag 187.0 g/t,Bi 1.1%,As 4.4%,and S 14.9%.The main phase composition includes lead sulfate（Pb SO₄）,arsenic trioxide（As₂O₃）,zinc sulfate monohydrate（Zn SO₄·H₂O）,copper sulfate（Cu SO₄）,zinc oxide（Zn O）,zinc sulfide（Zn S）,and copper sulfide（Cu S）.（2）The experimental research on the single factor of pressure deep leaching and simultaneous arsenic precipitation of copper smelting dust has found that increasing the reaction temperature,initial sulfuric acid concentration,and oxygen partial pressure can obtain better zinc and copper leaching rates;extending the reaction time,increasing the slurry liquid-solid ratio,and accelerating the stirring speed can effectively improve zinc and copper leaching rates and arsenic precipitation rate.The optimized technical parameters for pressure deep leaching and simultaneous arsenic precipitation of copper smelting dust are:reaction temperature of 160℃,reaction time of 3 h,initial sulfuric acid concentration of 40 g/L,pulp liquid-solid ratio of 5:1,iron-arsenic molar ratio of 1.3,oxygen partial pressure of 0.8 MPa,and stirring speed of 600 rpm.The results of the parallel experiment under this condition showed that the residual contents of zinc and copper in the leaching residues were 0.47%and0.66%,respectively,and the leaching rates of zinc and copper were both over 96%and 97%,respectively.The precipitation rate of arsenic was about 93%,and the arsenic content in the leaching residues was 9.84%,while the residual concentration of arsenic in the leaching solution was as low as 0.66 g/L.The enrichment multiples of lead,silver,and bismuth in the leaching residues were more than 2.8 times.（3）Temperature is a key factor that affects the proess of pressure leaching and synchronous arsenic precipitation and solidification during copper smelting.During the process of the reaction temperature increasing from 150℃to 160℃,the arsenic-rich phase in the leaching slag gradually transforms from the metastable amorphous iron arsenate（Fe As O₄·x H₂O）to the stable crystal scorodite（Fe As O₄·2H₂O）.The transformation of the leaching slag phase is divided into two stages:the first stage from 0 to 60 minutes mainly involves the dissolution of zinc sulfide and copper sulfide,while the second stage from 60 to 180minutes mainly involves the co-precipitation of arsenic and iron to generate scorodite.As the initial sulfuric acid concentration increases to 40 g/L,the thermodynamic stability zone of arsenic iron sulfate will gradually shrink,and the initial sulfuric acid concentration exceeding 45 g/L will not be conducive to the formation of scorodite.Increasing the molar ratio of iron and arsenic and oxygen partial pressure,the Fe（Ⅲ）in the system is prone to reach supersaturation state,which is conducive to the formation of scorodite,and at the same time,the unstable iron sulfates（Na₂Fe（SO₄）₂OH·3H₂O）also compete to precipitate.（4）The expanded experimental results of optimizing technical parameters for copper smelting dust pressure leaching and simultaneous arsenic precipitation show that the leaching rate of valuable metals,arsenic precipitation rate,and the composition and macroscopic morphology of leaching residue and liquid have reproduced the results of small-scale experiments well.This indicates that the obtained technical parameters are stable and reliable,laying a foundation for the industrial application of the new process of pressure deep leaching and simultaneous arsenic precipitation of copper smelting dust.