Separation Of Iron And Copper From Leaching Solution Of Spent Lithium-ion Batteries By Impregnating Deep Eutectic Solvent Resin

The effective recovery of spent lithium-ion batteries can not only generate significant economic and resource benefits,but also reduce their potential harm to the ecological environment and human health.Hydrometallurgy is the major process to recover spent LIBs,In this process,both impurity（Fe and Cu）and Ni,Co,Mn,Li are dissolved in leaching solution.In order to prepare new ternary cathode materials,Fe³⁺and Cu²⁺must be separated from the leaching solution.In view of the products purity obtained by the precipitation separation method is low and the large amount of organic waste is produced by extraction separation,a method for the separation of Fe³⁺and Cu²⁺from the leaching solution of LIBs by impregnating resin with the deep eutectic solvent was proposed.（1）The DES was prepared using trioctylmethylammonium chloride as a hydrogen bond acceptor and thymol as a hydrogen bond donor.The properties of this DES were characterized using NMR,viscometry and thermogravimetry to determine the generation of hydrogen bonds in the DES,the viscosity at different temperatures and the operating temperature range of the DES.The effects of DES composition,the concentration of Cl^-in the aqueous phase and other conditions on the extraction and separation performance of various metal ions in the leaching solution were investigated.On this basis,trioctylmethylammonium chloride-thymol DES1 with a molar ratio of 1:1 was selected for the preparation of impregnating resin.（2）The adsorption performance of the impregnated resin with DES1 as the extractant and XAD-4 as the carrier material was investigated.The results showed that under the conditions of 3mol/L Cl^-,0.1 mol/L H⁺,and a solid-liquid ratio of 20（g/L）,the removal efficiency of Fe³⁺was greater than 99%,Cu²⁺was lower than 20%,and the adsorption efficiency of the remaining metals was less than 13%.The kinetic fitting revealed that the Fe³⁺adsorption process was more suitable with the quasi-second-order kinetic model and the adsorption was controlled by chemical reactions.Through thermodynamic analysis,the Fe³⁺adsorption process was found to be by the Langmuir isothermal adsorption model.The analysis results of UV-Vis and FT-IR show that Fe³⁺and Cl^-form Fe Cl₄^-,and then exchange with Cl^-in DES1 that impregnated in resin.（3）To improve achieve the adsorption efficiency of Cu²⁺,DES2 was prepared using trioctylmethylammonium chloride and salicylaldoxime as the hydrogen bond acceptors and donors,respectively.Subsequently,the physical and chemical properties of DES2 were characterized and its extraction performance was investigated.A 1:2 molar ratio of trioctylmethylammonium chloride and salicylaldoxime was finally selected for the synthesis of DES2 for the preparation of impregnating resins.（4）The adsorption performance of Fe³⁺and Cu ²⁺from leaching solution of lithium-ion battery by（trioctylmethylammonium chloride-salicylaldoxime）/XAD-4 impregnating resin was studied further.The results showed that at 4 mol/L Cl^-and a solid-liquid ratio of 50（g/L）,the removal rate of Fe³⁺was>99%.After adjusting the p H=2 of the leaching solution,more than99%of Cu²⁺was removed at a solid-liquid ratio of 50（g/L）,while the adsorption rate of the remaining metals was less than 20%.This data proves that the adsorbent material is suitable for the removal of Fe³⁺and Cu²⁺from the leaching solution.The kinetic analysis showed that the Fe³⁺and Cu²⁺adsorption processes were well fitted with the quasi-second order kinetic model and controlled by chemical reactions.In addition,the thermodynamic analysis revealed that the Fe³⁺,Cu²⁺adsorption process was consistent with the Langmuir isothermal adsorption model.Mechanistic studies have shown that the adsorption of Fe³⁺is consistent with anion exchange.In contrast to Fe³⁺,the adsorption of Cu²⁺is due to the formation of chelates by copper and DES2 in the impregnating resin.In summary,the performance of two resins impregnated with DES for the removal of Fe³⁺and Cu²⁺from spent LIBs leaching solution was investigated and the adsorption mechanism was also explored in this paper.It provided a method and a process for removing Fe³⁺and Cu²⁺in leaching solution of spent lithium-ion battery.