Study On The Process And Mechanism Of Leaching Tellurium From Copper Anode Slime In Copper Slag

As one of the rare elements,tellurium is widely used in emerging industries such as metallurgy,chemical industry,and solar energy.In recent years,facing the current shortage of tellurium resources,its comprehensive recycling is particularly important.In the smelting industry,the main source of tellurium is copper anode slime,of which the proportion of rare precious metals is high.In this paper,the copper slag obtained from the comprehensive treatment of copper anode slime was used as the experimental material to study the efficient wet leaching and separation and recovery of tellurium.A process route for the treatment of copper slag by using field-enhanced alkaline leaching tellurium-reduction-purification-hydrolysis precipitation tellurium was proposed.Research indicates:（1）The E-pH diagrams of Te-H₂O,Pb-H₂O,Cu-H₂O,and Au-H₂O systems were plotted.The thermodynamic results showed that under alkaline conditions,the oxidant NaClO₃ can oxidize Te to TeO2,TeO₃^2-,HTeO4-,and TeO4^2-Au is oxidized to Au（OH）3.Due to its unstable nature and easy to continue oxidizing AuO2,Cu and Pb enter the solution in the form of Cu²⁺,HCuO^2-/CuO2^2-,PbO₃^2-,etc.,Au,Pt,and Pd Will not be leached.（2）Optimal conditions for ultrasonic assisted leaching in the outer field:at ultrasonic power of 150 W,leaching time of 30 min,alkali concentration of 1.2 mol/L,NaClO₃ addition amount is 1.5 times the quality of copper slag,liquid-solid ratio 9:1,the leaching temperature is 90℃,the stirring rate is 300 r/min,the leaching rate of tellurium reaches 93.31%.Optimal conditions for microwave-assisted leaching in the outer field:at microwave power of 700 W,microwave time of 4min,leaching time of 30 min,leaching temperature of 85℃,liquid-solid ratio of 10:1,NaClO₃ addition amount is 1.2 times of copper slag amount,NaOH concentration Under the leaching conditions of 1.4 mol/L and stirring speed of 300 r/min,the leaching rate of tellurium reached 91.97%.（3）Optimum conditions for ultra sonic-microwave synergetic oxidation leaching in external field:Optimized using RSM software to obtain the optimal conditions.The ultrasonic power is 414 W,the microwave power is 287 W,and the reaction time is 14 min.Under this optimized condition,The leaching rate of tellurium is 96.73%.In order to verify the validity of the model,three experiments were performed.The average leaching rate of tellurium was 93.4±0.95%.（4）Ultrasonic-assisted oxidative leaching of tellurium in the external field conforms to the Avrami model.Its apparent activation energy E is 27.63 kJ/mol,and the reaction process is controlled by a mixture of diffusion and interface chemical reactions.The kinetic equation is:-ln（1-x）=2368.47 exp（-27.63/RT）t0.630.（5）The reduction and purification process of the obtained tellurium leachate was experimentally studied using the Na₂SO₃ reduction method.The optimal conditions for reduction are:the amount of Na₂SO₃ is 1 times the theoretical amount,the reduction time is 9min,and the reduction temperature is 70℃.The concentration of Te（IV）in the solution was as high as 92.27%.（6）The Na₂S precipitation method was used to conduct an experimental study on the purification process of the reducing solution.The optimal conditions for removing impurities are:The amount of Na₂S is twice the theoretical amount,the purification time is 10 min,and the purification temperature is 60℃.The removal rates of Pb and Cu were 86.8%and 95.7%,respectively.Tellurium recovery was 96.52%.（7）The obtained purified solution was neutralized and hydrolyzed and precipitated tellurium was experimentally studied.The optimal hydrolysis and precipitation process is as follows:the endpoint pH is about 3.97,the hydrolysis time is 10 min,and the hydrolysis temperature is 90℃.The purity of crude TeO2 is≥85%.