Preparation Of Fe-Cu/Kaolin Partcle Electrode And The Study Of 3D/EF System

The electrochemical oxidation technology has been widely used in organic wastewater treatments.Three-dimensional electro-Fenton system(3D/EF),combining the advantages of both three-dimensional electrode system and electro-Fenton system,has the merits of highi catalytic efficiency,low energy consumption,environmental compatibility.However,the conventional 3D/EF system has the following drawbacks:the requirement of adding iron salt as a source of Fenton reagents,the difficulty of controlling ferrous salts dosage,complex operation,narrow working pH range,the difficulty of recovering the catalyst,as well as the need of disposal of iron sludge,which would increase the treatment cost.The problem of recovering the catalyst could be solved by supporting the iron ions on particle electrode.Nevertheless,the issue of working within narrow pH ranges still remains.Cu carn catalyze H2O2 decomposition as Fenton-like catalyst,facilitate the reduction of the Fe(?)to Fe(?),and extend the application pH range,owing to its Feonton-like catalytic activity and Lewis acid properties.In this study,we attempted to prepare novel Fe-Cu/kaolin particle electrode according to grinding-impregnated-molding-calcination procedure,and use the as-synthesized particle electrodes as effective multifunctional material in 3D/EF system.The optimal preparation conditions of the particle electrodes were dertermined by single factor experiment and orthogonal experiment.The particle electrodes with good performance obtained under the optimal preparation conditions were used for Rhodamine B(RhB)removal in the 3D/EF system.The effects of some important factors on RhB oxidation were investigated,and the optimal reaction conditions of 3D/EF system were obtained.The main conclusions of this paper are listed as follows:(1)According to single factor experiment and orthogonal test during grinding-impregnated-molding-calcination procedure,the optimal preparation conditions for the Fe-Cu/kaolin particle electrodes were:material ratio of 6:4,catalysts loadings of lwt%Fe lwt%Cu,the calcination temperature of 350?,and the calcination time of 3 h.(2)The Fe-Cu/kaolin particle electrodes obtained from the best preparation conditions were characterized.XRD showed that the original structure of kaolin could be maintained after loading Fe and Cu on it and forming the Fe-Cu/kaolin particle electrode;and the compositions of the catalytic components were mainly ?-Fe2O3 and CuO.FE-SEM showed that FeCu composite oxide was homogeneous spherical structure.EDS confirmed FeCu composite oxide was successfully loaded on the particle electrode.The specific surface area analysis revealed that the specific surface area of the FeCu composite oxide loaded particle electrode increased.(3)The effects of various parameters on RhB degradation were investigated in the 3D/EF system with Fe-Cu/kaolin particle electrodes.With the 20 mg/L RhB solution(400mL)in the 3D/EF system,RhB degradation of 94.8%could be achieved within 60 min under conditions of using the dosage of particle electrodes of 30 g/L,the electrolytic voltage of 10 V,initial pH of 6.71,and airflow rate of 0.8 L/min.This indicated that the Fe-Cu/kaolin particle electrodes can be used in a wide pH range.In the 3D/EF(Fe-Cu/kaolin)system,RhB degradation was much more efficient as compared with those using activated carbon particle electrodes and kaolin particle electrodes.Energy consumption analysis results showed that the energy consumption of the 3D/EF(Fe-Cu/kaolin)system(68.58 kWh/m3)was much lower than the two-dimensional electrode system,3D(activated carbon)and 3D(kaolin)systems,and the energy consumption was reduced by approximately 1/43,1/9 and 1/8,respectively.(4)After Fe-Cu/kaolin particle electrodes were used over five cycles,the removal efficiency of RhB was 82.1%,which indicated an outstanding recycling capacity and stability for long-term electrocatalytic reaction.(5)The UV-vis spectra changes and TOC removal efficiency indicated that RhB was partly mineralized to CO2 and H2O,and partly oxidized into intermediates.From the scarvenging experiment,it was found that ·OH played an important role in RhB oxidation degradation process.Besides,particle electrodes absorption,and electrodes' surface oxidation also contributed to RhB removal.(6)It was assumed that all the degradation processes of RhB followed pseudo-first order reaction kinetics,and the results confirmed this assumption.The rate constant(0.06971 min-1)of 3D/EF system was much higher than the sum of adsorption experiment of Fe-Cu/kaolin and two-dimensional electrode system(0.0139 min-1),which implied other reactions might occur except adsorption and anodic oxidation.Homogeneous oxidation and heterogeneous oxidation also played an important role in 3D/EF(Fe-Cu/kaolin)system.