Study On Technologies Of Selective Leaching And Recovery Of Selenium And Tellurium From Copper Anode Slimes

With the increasing complexity of raw materials for copper smelting,the contents of selenium,tellurium,and other scattered metals in the copper anode slime（CAS）fluctuates greatly.Problems such as high energy consumption,low leaching efficiency of selenium and tellurium,low separation efficiency of selenium and tellurium still exist in the conventional pyrometallurgical,hydrometallurgy,and combined technologies.In order to overcome these challenges,two processes for the removal of selenium and tellurium from CAS have been investigated in this thesis,one is the leaching of tellurium and arsenic with（NaOH+Na₂S）solution followed by the leaching of selenium with NaOH solution in oxygen pressure;the other is the leaching of selenium and arsenic using NaOH at oxygen pressure condition followed by the leaching of tellurium with Na₂S solution.The reduction of tellurium from the Na₂S leachate with Na₂SO₃or SO₂was explored.The results are as follows:（1）The performances of tellurium and arsenic removal in the leaching of tellurium and arsenic with（NaOH+Na₂S）followed by the leaching of selenium using NaOH via oxygen pressure were investigated.Under the conditions of[Na₂S]/[Na⁺]_Tmolar ratio of 0.2,[Na⁺]_Tof 3.48mol/L,liquid-solid ratio of 7:1 m L/g,120℃,4.5 h,and the leaching efficiencies of tellurium,arsenic and selenium in the（NaOH+Na₂S）solution leaching stage were 88.4%,99%,and 3.4%,respectively.Under the conditions of[NaOH]of 1.5 mol/L,5.0 h,200℃,liquid-solid ratio of6:1 m L/g,oxygen partial pressure of 0.45 MPa,99%of selenium in the oxygen pressure NaOH leaching stage could be obtained;meanwhile,copper,silver,tellurium,and antimony enriched in residue.（2）The leaching efficiency of selenium,arsenic and tellurium was studied in the process of the leaching of selenium and arsenic using NaOH via oxygen pressure followed by the leaching of tellurium with Na₂S,under the conditions of[NaOH]of 1.5 mol/L,liquid-solid ratio of6:1 m L/g,oxygen partial pressure of 0.45 MPa,200℃,5.0 h,96.7%of selenium and 95.9%of arsenic could be leached in the oxygen pressure NaOH leaching stage.Under the conditions of[Na₂S]of 1.0 mol/L,liquid-solid ratio of 10:1 m L/g,80℃,1.5 h,the leaching efficiency of tellurium in the Na₂S leaching stage was 94.3%.Copper,silver,gold,etc.enriched in residue.（3）Two methods for recovering tellurium from Na₂S leachate were explored.Under the conditions of excess coefficient of Na₂SO₃of 18.08,40℃and 30 min,89%of tellurium was recovered and a tellurium product with a tellurium content of 93.2%was obtained.With the SO₂flow rate of 30 m L/min and duration of ventilation of 45 min,99%of tellurium was recovered at 40℃and a sample with 87.5%tellurium was produced.The oxidation of tellurium in the process could explain the low tellurium content in the product.