Construction Of A Capacitive Deionized Electrode For Selective Removal Of Pb²⁺

Heavy metal lead（Pb）pollution is characterized by difficult natural degradation,easy accumulation,and high toxicity,and long-term exposure can cause irreversible damage to human body,while Pb is also an important non-renewable resource.Selective and efficient removal and recovery of Pb²⁺from complex water bodies is of urgent practical importance and also an important proposition for separation science and technology.Capacitive deionization（CDI）technology is easy to operate,energy efficient,environmentally friendly,and feasible for selective electrosorption removal of Pb²⁺from water bodies,but it is still challenging in the construction of CDI electrode materials.In this paper,we propose a tannin/Mo O₂ construction strategy using nickel foam as the collector and loading the surface of high specific capacitance Mn₂Co O₄ coating material to achieve selective adsorption and desorption of Pb²⁺,and explore the capacitive removal,selective properties and mechanism of action of the two constructed electrodes for Pb²⁺in drinking water and industrial heavy metal wastewater,respectively.The results provide a feasible technical approach for the selective and efficient removal of Pb²⁺in complex water environments,and actively contribute to the design and construction of high-performance CDI electrode materials for practical engineering development.The main research contents are as follows:（1）In the study of selective removal of Pb²⁺from drinking water,Mn-doped Co₃O₄nanopins were generated on the surface of nickel foam using hydrothermal method,Fe（III）was used as a cross-linking agent,and tannic acid（TA）was loaded on the surface of the nanopins to synthesize NF/Mn₂Co O₄@TA-Fe³⁺electrode material,and this electrode has low resistance and good charge transfer property.The feasibility of selective capacitive removal of Pb²⁺from drinking water was investigated by making it the negative electrode and graphite paper the positive electrode to form an asymmetric CDI system.The results showed that the removal of a single Pb²⁺reached 100%at 1.4 V,and the electrode adsorption capacity was as high as 375 mg g^-1 in a 100 ppm solution with good electrochemical stability;the electrode had excellent selective adsorption performance for Pb²⁺in solutions containing a variety of harmless competing ions,and this selective adsorption was due to the electrode surface loading of TA-Fe³⁺The specific adsorption site（phenolic hydroxyl group）formed a complexation with Pb²⁺that is significantly stronger than the electrostatic force between other cations and the electrode,which can achieve stepwise separation.（2）In the study of selective removal of Pb²⁺from industrial wastewater,Mo O₂ was prepared on the surface of NF/Mn₂Co O₄ by electrochemical deposition,and NF/Mn₂Co O₄@Mo O₂composite electrode was synthesized,which showed pseudo-capacitive characteristics of rapid redox reaction in Pb²⁺solution.The asymmetric CDI system was composed of NF/Mn₂Co O₄@Mo O₂ and graphite paper,and the concentration of Pb²⁺in the solution decreased from 50 ppm to 4 ppb after adsorption for 1 h at 1.4 V.It showed excellent adsorption performance,and its adsorption capacity reached 156.24mg g^-1;in the mixed solution containing various heavy metal ions,this electrode exhibited good.The analysis of the adsorption mechanism showed that during the adsorption process,Pb²⁺was embedded in the interlayer of Mo O₂,which disturbed the symmetric structure of the electron cloud and caused the lattice change of Mo O₂,resulting in the formation of Pb Mo O₄,thus achieving the selective removal of Pb²⁺.