| In recent years,environmental pollution problems caused by excessive nitrogen group elements(such as phosphorus and antimony)in water has attracted widespread attention in the international community.It is urgent to develop targeted technologies for in-depth removal of nitrogen group pollutants in water.Compared with existing treatment technologies,adsorption is a potentially feasible technology for water pollution treatment because of its simplicity of operation,high treatment efficiency,wide range of applicable water bodies,and reusability.Among them,metal-organic frameworks(MOFs)are promising porous adsorption materials,but there are still shortcomings such as easy agglomeration,difficult recovery,and slow adsorption kinetics.In this paper,we propose to develop MOFs-functionalized carbon nanotubes(CNTs)nanocomposite membrane materials to solve the above problems.Two penetrating electric filtration systems based on cerium-based organic frameworks(Ce-MOF)and zirconium-based organic frameworks(UiO-66(Zr))modified CNT filters were designed to achieve efficient removal of typical nitrogen group pollutants(phosphate and antimony(Ⅲ))from water by using an auxiliary electric field to induce redox reactions and a penetrating design to enhance the kinetic process of pollutant removal.Details of the study are as follows.(1)Ce-MOF/CNT system: Aiming at the problem of phosphate removal in water,an electroactive Ce-MOF/CNT composite membrane was prepared and a penetrating electric filtration system was constructed.The physicochemical properties of the composite membranes were systematically characterized by advanced characterization techniques,and the structureactivity relationships between the operating process parameters such as Ce-MOF loading,voltage,flow rate and phosphorus removal performance were established.The results showed that under the optimal conditions of 1.0 m M Ce-MOF loading,2.0 V voltage and 4.5 m L/min flow rate,the maximum phosphate adsorption capacity of Ce-MOF/CNT filter was 22.41 mg/g,and the phosphate adsorption kinetics of Ce-MOF /CNT filter was improved by 5.8 times compared with the sequential batch operation mode.The main phosphate adsorption mechanisms include outer spherical surface complexation(electrostatic attraction),inner spherical surface complexation(CeO-P)and diffusion.In addition,the effects of organic and inorganic interference components on the phosphate removal performance of Ce-MOF/CNT filter were investigated through the coexistence anion experiment and the simulated phosphate-spiked lake water experiment.After three cycles of regeneration,the phosphate removal efficiency of Ce-MOF/CNT filter can still reach 92.8%,showing excellent stability and practicability.(2)UiO-66(Zr)/CNT system: Aiming at the antimony(Ⅲ),with the pollution characteristics of high toxicity,low concentration,and electrical neutrality,in water.An electroactive UiO-66(Zr)/CNT composite membrane was designed and developed to achieve antimony(Ⅲ)detoxification and adsorption simultaneously with the aid of an auxiliary electric field.It was shown that the UiO-66(Zr)loading,electric field strength and penetrating operation mode played a key role in the removal of antimony(Ⅲ).The maximum adsorption capacity of the prepared electroactive UiO-66(Zr)/CNT filter was 11.68 mg/g for total antimony.The oxidation-adsorption mechanism of the filter on antimony(Ⅲ)was elucidated through XPS characterization and valence analysis,and the effect of coexisting anions on the removal of antimony(Ⅲ)by UiO-66(Zr)/CNT filter was investigated.After five cycles of regeneration,the UiO-66(Zr)/CNT filter still achieved 88.6% removal of antimony(Ⅲ),which has good stability and practical application potential.In summary,the developed penetrating electrochemical system in this thesis couples the advantages of electrochemistry,membrane separation and nanotechnology,and provides a potentially feasible theoretical basis and technical reference for the efficient removal of nitrogen group pollutants in water. |
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