Preparation Of HCPs/PPy Hierarchically Porous Composite Electrode Materials For Heavy Metal Ions Adsorption

The issues of energy scarcity and environmental degradation have recently come into greater focus.Heavy metal ions wastewater seriously threatens the ecological balance and human health due to its high toxicity,long toxic effect time,and non-degradable characteristics,making it becomes one of the difficult problems in the process of managing environmental pollution.Capacitive deionization（CDI）technology achieves the adsorption and de-concentration of heavy metal ions through the adsorption/desorption process of electrode materials.As one of the most valued emerging heavy metal ion wastewater treatment technologies in recent years,it has the advantages of high efficiency,simple operation,regenerable electrodes,and environmental friendliness,and also has a wide range of potential industrial applications.Electrode materials as the core part of CDI technology,it is extremely important to select,develop and modify them.Currently,how to construct and regulate the pore size structure of CDI electrode materials becomes a major hot spot.The microporous,mesoporous,and macroporous pore diameters of the hierarchically porous electrode material can reduce the ion transport path and increase transport efficiency.The composite electrode material is compounded with conducting polymers to improve the conductivity of the electrode while having a good hierarchically porous structure and is applied to the field of CDI heavy metal ion wastewater treatment.In this thesis,to address the issues of pore size structure and poor conductivity,preparing the carbon-based materials with hierarchical pore size by carbonization of cross-linked polymers（HCPs）,then the HCPs/PPy composite materials were constructed by doping conductive and stable polypyrrole（PPy）under electrodeposition.After that,to further simplify the electrode forming steps and improve the pore size structure,the HCPs/PPy/PVA composite materials were prepared by electrostatic spinning.A variety of characterization experiments were used to investigate the morphology,structure,and electrochemical characteristics of the HCPs/PPy/PVA composite materials.The adsorption performance of the composite electrodes was tested under the conditions of different concentrations and types of heavy metal ion solutions with an applied voltage to investigate the connection between the graded porous structure and the adsorption performance.The following conclusions were obtained by establishing adsorption models and exploring the adsorption mechanism.（1）In this study,the HCPs/PPy composited materials with hierarchically pore size were obtained by a combination of hydrothermal-carbonization and electrochemical deposition.The composites with different pore size structures were prepared by varying the additions of polyacrylamide（PAM）and activator Na OH.The experimental results showed that HCPs/PPy had a honeycomb pore structure under the preparation conditions of 1.5 g of PAM and 0.5 g of Na OH,the microporous content is 69.2%,the mesoporous content is 21.2%,and the macroporous content is 9.7%.The electrochemical and adsorption properties of the composite electrode are also superior.The specific capacitance was obtained as 339.66 F/g,and the adsorption amounts of Na⁺,Cu²⁺,Pb²⁺,and Fe³⁺were 20.69 mg/g,37.81 mg/g,26.76 mg/g,and 40.95 mg/g,respectively.In addition,it had excellent cycling stability,and the regeneration rate could still be maintained at 97.61%after 10 times of adsorption/desorption tests.This study shows that the HCPs/PPy composites have good adsorption and excellent stability（2）To further simplify the electrode preparation process,improve the pore size structure of materials and enhance the adsorption performance and ions transport efficiency.The HCPs/PPy/PVA materials were prepared in the one-stepping electrostatic spinning method in this study.Through FT-IR,electrochemistry tests proved that the best preparation condition is 9%PVA and 0.5%PPy addition concentration,the specific surface area of the prepared HCPs/PPy/PVA composite electrode reached 458.98 m²/g,and the adsorption capacity of Cu²⁺could reach 82.83 mg/g,and the capacitance retention was also maintained at 98.85%,indicating excellent cycle stability.Compared with HCPs/PPy composites,the HCPs/PPy/PVA composite electrodes formed by electrostatic spinning have a larger specific surface area and higher heavy metal ion adsorption capacity.This study provides a unique idea for the preparation of CDI electrode materials in the field of heavy metal ion adsorption.