Electrochemical Hydroge Nevolution Reinforced Zero-valent Iron For The Reduction Of Nitrate

Nitrate contamination in surface water has regarded as the main concern in the field of water environment protection all over the world.Excessive nitrate in surface water can not only lead to red tide phenomenon but also have detrimental effects to human health.The development of a new type of nitrate disposal technology has become a hot spot in this field.Among the employed techniques,the chemical reduction of nano zero-valent iron（Fe⁰）and electrochemical technologies have garnered the significant attention of researchers for their eco-friendly and cost-effective in engineering applications.However,the practical application of Fe⁰is greatly limited by its disadvantages of easy oxidation and poor stability.To maintain the high reactivity and durability of Fe⁰in solution,we combine Fe⁰with electrochemical hydrogen evolution reaction（HER）and explore the practical application field of the composite system.The details as follows:Fe⁰ nanoparticles and Ni₂P/CC electrode were synthesized by liquid-phase reduction and electroless plating as well as phosphation method,and then characterized using X-ray diffraction and Scanning electron microscopy analyzer.Nitrate disposal efficiency was extensively investigated via batch experiments under different conditions（reaction time,Fe⁰dosage,pH,current density and distinctive nitrate concentrations）.Comparing the nitrate removal efficiencies with Fe⁰+Ni₂P/CC,pure HER and pure Fe⁰systems,Fe⁰+Ni₂P/CC can remove 94.71%nitrate in the simulated wastewater under at the optimal condition,and the final total nitrogen（TN）concentration was reduced to 1.17 mg/L,consistent with V-level requirement of surface water environmental quality.It found that the reduction kinetics of nitrate removal obeys the first-order equation.Also,the spent Fe⁰nanoparticles can be used to catalyze the decolorization of dyes via hydrogen peroxide oxidation process,which could obtain almost 91.26%decolorization rate.In our study,we prepared a novel catalyst cathode（Fe⁰/Ni₂P/CC）using liquid-phase reduction method to load Fe⁰nanoparticles on the surface of Ni₂P/CC,which expands the scope of engineering application.Based on the results of microscopic morphology,chemical composition and chemical valence obtained from XRD,SEM,and XPS,we conclude that the chain-shaped multiple Fe⁰nanoparticles were excellently anchored on the surface of Ni₂P/CC electrode.At the condition of the employment of optimized parameters,the feasibility for actual NO₃^--contaminated wastewater treatment were extensively investigated.As a result,under the condition of pH=7,current density=25m A/cm²and initial concentration=15 mg/L,approximately 89.81%NO₃^--N is removed by Fe⁰/Ni₂P/CC electrode within 4 h,and N₂ selectivity is 96.94%.TN concentration reduces to 1.94 mg/L,which completely meets the maximum threshold value（2.0 mg/L）for V-level surface water environmental quality.In addition,we calculated the Coulomb efficiency（CE）and Faraday efficiency（FE）,which were that:CE=38.68%and FE=43.07%.Fe⁰/Ni₂P/CC electrode has an excellent recycling performance and can be regarded as an iron-based catalyst in the chemical advanced oxidation process.The electroreduction pathway of nitrate reduction consists of significant processes,i.e.,the adsorption hydrogen,the hydrogen and iron redox reaction.