Study On 3D Graphene/CeO₂-based Composite Cathode Materials For The Degradation Of Ciprofloxacin By Electro-Fenton Method

The effect of electrochemical advanced oxidation processes(EAOPs)treats organic wastewater depends on the nature of the electrode material.To choose suitable cathode materials can not only inhibit hydrogen evolution reaction on the cathode,but also can produce strong oxidizing substances such as H2O2 and ?OH by the cathodic reaction to increase the effect of degradation of organic matter and reduce the energy consumption of the electrochemical reaction.In this paper,we take the three-dimensional graphene which has porous structure as conductive material,successfully synthesized 3D CeO2/RGO and 3D CexZr1-x O2/RGO composite cathode.The degradation effect of ciprofloxacin was explored by electro-Fenton oxidation method.The electro-Fenton method is that make the oxygen occur reduction reaction on the cathode by oxygenation or aeration and indirectly produce Fenton reagent H2O2 by electrolysis,then Fe2+ catalyzes H2O2 continuing to produce hydroxyl radicals which have strong oxidation property,thus achieve efficient degradation of organic pollutants.This method has many advantages such as low cost,no special requirements on the equipment and simple operation.The graphene oxide was prepared by Hummers oxidation method.The 3D CeO2/RGO and 3D CexZr1-x O2/RGO composite cathode were prepared through the method of hydrothermal self-assembly of graphene and in-situ deposition of CeO2 nanoparticles or CexZr1-x O2 solid solution.At the same time,the preparation conditions were optimized.The morphology and structure of the composite electrodes were analyzed by means of transmission electron microscope,scanning electron microscope,X-ray diffraction,nitrogen adsorption-desorption isotherm,X-ray photoelectron spectroscopy and other methods.The electrochemical properties of the composites were analyzed by cyclic voltammetry and electrochemical impedance spectroscopy.The effects of 3D CeO2/RGO and 3D CexZr1-x O2/RGO composite cathodes on the degradation of ciprofloxacin were investigated by UV visible absorption spectroscopy(UV-vis)and total organic carbon(TOC)and the conditions for the degradation of ciprofloxacin on composite cathodes were optimized.We studied the influence of the initial pH value,the current intensity,the amount of catalyst Fe2+,the hydrothermal reaction time,the doping of Zr,the load capacity of cerium zirconiumsolid solution oxide and ratio of cerium and zirconium on the effect and mechanism of the efficiency of electro-catalytic oxidation degradation of ciprofloxacin.The research results show that when the initial pH value was 3,the current intensity was 400 mA,the amount of catalyst Fe2+ was 0.1 mmol?L-1,the hydrothermal reaction time was 8 h,the efficiency of electro-catalytic oxidation of ciprofloxacin was the highest.When we used the 3D CeO2/RGO electrode,the highest degradation efficiency of ciprofloxacin was 100% after 6.5 h measured by UV,TOC removal rate was 90.97%.When Zr was doped into CeO2,the degradation rate was obviously accelerated.When the mass ratio of cerium nitrate and zirconium nitrate was 30:10,we get the 3D Ce0.75Zr0.25O2/RGO electrode,the highest degradation efficiency of ciprofloxacin was100% only after 5 h measured by UV,TOC removal rate was 96.38%.