Application Of Potential-responsive Materials In Removal Of Trace Heavy Metals And Recovery Of Lithium Ions

With the continuous expansion of modern industrial production,energy shortages and environmental pollution have become hot topics recently.Wastewater from industrial processes contains many toxic metal ions,such as Cd²⁺,Pb²⁺and Hg²⁺,which are harmful to humans and other species and reducing the Hg²⁺and other toxic heavy metals to trace levels(<5 ppb,ug·L^-1)remain a major scientific challenge.In addition,,the number of waste lithium batteries has sharply increased with the rapid development of the lithium battery industry,which contains 5-15%cobalt,2-7%lithium,nickel,manganese,copper and other precious metals.Lithium batteries will cause great harm to the environment if they are directly discharged into the environment.Effective recovery of precious metals from used lithium-ion batteries can not only reduce the harm to the surrounding environment,but also save natural resources.which is of great significance for the sustainable development of the entire society.Therefore,searching for a simple,green,and efficient separation and recovery of ions is imminent.In this study,Potential-Responsive Sulfide Conductive Film?P-RSCF?was prepared by the combined action of elemental sulfur and polypyrrole?PPy?.The preparation method has the advantages of simple synthesis,low cost and no secondary pollution.In addition,the rate of ion migration in the solution is greatly increased by the electric field driving and the removal rate of metal ions is significantly increased.P-RSCF exhibits a excellent adsorption capacity for heavy metal ions(maximum Cd²⁺adsorption capacity q_m reaches 3400 mg·g^-1).For highly toxic Cd²⁺,Cu²⁺,Pb²⁺,Ag⁺and Hg²⁺?initial concentration is 1000 ppm?,the removal rate reaches 99.9%within 20 min and the partition coefficient is K_d>10⁵ mL·g^-1.In the single adsorption experiments,the concentration of Hg²⁺in the solution rapidly decreased from 49.53 ppm to a trace level of?1 ppb and the partition coefficient was K_d>10⁷ mL·g^-1,otherwise the removal efficiency of other heavy metal ions also reached the industrial wastewater discharge standard.X-ray diffraction,scanning electron microscopy,and X-ray photoelectron spectroscopy were used to characterize the morphology and structure of the materials during the experiment.As a result,it confirmed that the sulfur exist in the membrane electrode and the heavy metal ion in the solution were combined in the form of an M-S covalent bond.Therefore,P-RSCF shows strong affinity for heavy metal ions.In addition,commonly used cathode materials for lithium ion batteries include lithium cobalt oxide?LiCoO₂?,lithium manganese oxide?LiMn₂O₄?,lithium nickel cobalt manganese oxide?NCM?ternary materials,and lithium iron phosphate?LiFePO₄?.Among them,lithium cobaltate?LiCoO₂?is currently the most widely used type of lithium battery material,and is mainly used in high-end electronic products such as notebook computers and mobile phones.In this study,Electrochemically Switched Ion Exchange?ESIX?technology and biological coupling technology are used to recover metallic lithium in waste lithium battery.In this study,nano-cubic structure of Ferricyanide?FeHCF?is used as a lithium extraction electrode.The factors of different matrix materials,operating voltage and initial concentration on the effect of lithium extraction were investigated.The microstructure and elemental composition of FeHCF were characterized by scanning electron microscopy?SEM?and X-ray diffraction?XRD?.Experimental results show that the FeHCF electrode with Ni foam has excellent lithium extraction performance.The concentration of Li⁺was reduced from 1399 mg·L^-1to 877 mg·L^-1,and has a high recovery rate of 90%in bioleaching solution of iron phosphate batteries.The deinterealate efficiency of the membrane electrode has been kept at a high level?>90%?,demonstrating excellent cycle stability after multiple interealate and deinterealate cycles experiments.This intelligently technology should be a promising alternative method for the lithium ions removal from waste lithium battery.In this study,the potential-responsive materials were prepared by a simple,low-cost method,which not only greatly improved the removal efficiency and the adsorption capacity of heavy metal ions,but also showed an excellent separation effect on the lithium metal in the leachate of waste lithium batteries.The potential-responsive material takes the potential as the driving force,which avoids the problems such as complicated operation,high energy consumption and easy secondary pollution caused by traditional separation and recovery methods in removing heavy metals and recovering lithium metal.Therefore,the potential-responsive material is an environment-friendly new separation and recovery technology,which is of great significance for environmental protection,saving precious metals,and improving resource utilization.