Leaching Characteristics Of Copper From Copper-rich Electroplating Sludge By Ionic Liquids And Its Electrodeposition Recovery

Electroplating sludge（ES）is a double-edged sword（hazards and resources）,so it is essential for reclamation management and recycling metals for clean production,resource recovery and environmental protection.Hydrometallurgy is the primary method to regenerate valuable metals from ES and reduce their environmental hazards.The selection of efficient and environmentally friendly leaching agents is the key to metal leaching and recovery.Ionic liquids（ILs）are low volatile,corrosive,and recyclable,providing high electron conductivity.They are a good choice of green,efficient reagents,and efficient and help streamline the recovery process.To compare the influence of cation on ILs copper leaching,four ILs（Non-functional ILs:[BMIm]HSO₄,Functional ILs:[HOOCMIm]HSO₄,[BSO₃HMIm]HSO₄ and[BSO₃]Py.HSO₄）were used to leach Cu from copper（Cu）rich electroplating sludge（C-ES）.The leaching behavior and rule of Cu in ILs were analyzed,and the leaching conditions were optimized by an orthogonal test.Based on the structural changes of ILs and C-ES before and after leaching,the mechanism of functionalized ILs cations on increasing Cu leaching efficiency was further discussed.Secondly,Cu and regenerated leaching agent were recovered from Cu-ILs leaching solution by electrodeposition.The leaching and electrodeposition process were coupled as a closed-loop process to preliminarily evaluate its recyclability.The main research results are as follows:（1）ILs leaching agent usage（concentration and dosage）,oxidizer（H₂O₂）dosage,leaching time and the temperature had essential effects on Cu leaching efficiency.The influence degree of main operating factors on Cu leaching was ILs concentration>ILs dosage>H₂O₂ dosage>time and temperature,Cu was completely leached under the optimal leaching conditions（ILs concentration 4%,dosage 10 m L,H₂O₂ dosage 0.5 m M）.The Cu leaching efficiency was linearly correlated with ILs concentration,dosage and oxidant dosage（Y=19.867+11.665X₁+7.841X₂+10.857X₃）.（2）The Cu leaching capacity of ILs is related to the cationic group type and functionalization.Under low concentration conditions,the Cu leaching efficiency of ILs functionalized by-COOH/-SO₃ is significantly higher than that of ILs not functionalized,and sulfonic acid functionalized ILs is more conducive to Cu leaching.Functionalization of ILs improves Cu leaching rate mainly by increasing H⁺in the leaching system,but imidazolyl ILs have a slightly weaker H⁺providing ability than pyridinyl ILs,and the introduction of specific functional groups has a greater effect on H⁺providing ability than cationic groups.Functional ILs leaching of Cu involves ion exchange and the use of-COOH/-SO₃ and Cu²⁺complexation,while the leaching mechanism of non-functional ILs is only ion exchange.（3）The process of leaching Cu from C-ES using ILs was ascribed to the chemical reaction between ILs and copper oxide of C-ES and the mass transfer behavior between the liquid–solid phase.The leaching kinetics accords with the shrinking core model controlled by chemical reaction and diffusion.The apparent activation energies of the four ILs leaching Cu were 39.21,0.98,14.47 and 41.93 k J mol^-1,respectively.（4）Cu recovery and ILs regeneration can be realized simultaneously by electrodeposition.Under optimal conditions,the recovery of Cu in the leaching solution is up to 99.1%,and the purity of Cu in the electrodeposited product is up to 95.44wt%.Increasing the Cu concentration and applied current in the electrolyte has a positive effect on Cu recovery.The product in the flowing state is dense and smooth,while the product in the static state is fluffy and porous.（5）The process of Cu recovery from C-ES by leaching[BSO₃]Py.HSO₄ and electrodeposition are effectively coupled,and the steps of Cu recovery are significantly shortened.The process has high Cu recovery and good recycling.ILs is effectively recycled,the system solution reuse rate is greater than 98%,and the leaching toxicity of Cu from solid waste was significantly reduced.