A Study On Recovery Of Copper From Reclaimed Copper Smelting Fly Ash

Reclaimed copper smelting fly ash（referred to as fly ash）is the residue generated during the smelting process of reclaimed copper,which contains valuable resources such as Cu and Zn.Therefore,the recovery of metals such as Cu and Zn in fly ash is of great practical significance for the recovery of valuable resources in the reclaimed copper industry.Taking fly ash as the research object,the thesis carried out research on the basic physical and chemical characteristics of fly ash,the recovery of Cu by acid leaching and electrodeposition of fly ash,the leaching law of valuable metals in the ammonia leaching system of fly ash,and the recovery of Cu by slurry electrolysis of fly ash,forming a high-efficiency leaching of valuable metals such as Cu and Zn and the recovery technology of Cu in fly ash.The research results of this paper will provide theoretical and technical support for the recovery of valuable resources in fly ash.The main conclusions are as follows:（1）By analyzing the basic physical and chemical properties of fly ash,it can be seen that the leaching concentrations of Cd and Pb in fly ash exceeds the threshold in the HJ/T 299-2007leaching toxicity method and the TCLP leaching toxicity method.Extraction of metals in fly ash by EDTA method and DTPA method shows that the order of metal content in fly ash is Zn>Cu>Pb>Se>Cd>Au>Sb>Ba>Be and Zn>Cu>Se>Cd>As>Pb>Au>Sb>Ba>Be.In addition,Cu and Zn in fly ash pose significant risks to the environment and human health,but Ba,Cd,Au,Se,Ni,Sb,and Be have lesser risks.（2）The research on the recovery of copper by acid leaching and electrodeposition of fly ash is carried out.The research results show that under the conditions of mass ratio of fly ash to sulfuric acid 1:0.5,solid-liquid ratio 40 g/L,reaction temperature 50℃,leaching time 1 h,the leaching rates of Cu,Zn and Cd in fly ash are 92.52%,96.84%and 92.57%respectively.In addition,when the current density is 40 m A/cm²and the electrolysis time is 90 min,the recovery and purity of copper are 94.69%and 99.21%,respectively.（3）The leaching law of valuable metals in the ammonia leaching system of fly ash is studied.The results show that appropriately increasing the ammonia concentration is beneficial to the formation of copper-ammine complexes and improves the leaching rate of Cu in fly ash.Under the conditions of ammonia concentration of 1 mol/l,ammonium chloride concentration of 1 mol/l,solid-liquid ratio of 125 g/l,reaction temperature of 30℃and leaching time of 60 min,the leaching rates of Cu,Zn and Cd in fly ash are 89.45%,78.75%and 82.34%respectively.The results of leaching kinetic analysis show that the rate-limiting step of copper leaching process from fly ash is controlled by internal diffusion.（4）The research on the recovery of copper by slurry electrolysis from fly ash is carried out.The results show that under the conditions of ammonia concentration of 2 mol/L,ammonium chloride concentration of 1 mol/L,Cu²⁺concentration of 20 g/L,solid-liquid ratio of 50 g/L,current density of 30 m A/cm²,and electrolysis time of 2 h,the recovery rate and current efficiency of copper in fly ash are 97.11%and 91.22%,respectively,and the purity of copper in the cathode product is 99.45%.In addition,increasing the concentration of Cu²⁺in the slurry electrolysis system increases the cathode overpotential,accelerates the deposition rate of cathode copper,is conducive to the formation of dense elemental copper products at the cathode,and helps to improve the current efficiency of copper in the slurry electrolysis system.