Preparation Of Hydrogen Peroxide In Situ And Degradation Of Typical Pollutants Using Carbon Modified Cathode Electrolytic Cell

The electro-Fenton technology,which can produce H₂O₂ in situ,has become one of the research hotspots in recent years because of its unique advantages in the treatment of refractory organic sewage,in which cathode materials,catalysts and reactors are the focus of research.This paper mainly carried out studies on screening and modification of cathode materials,optimization of electro-Fenton system reaction conditions,construction of air cathode electro-Fenton reactor and heterogeneous Fe-C catalyst and evaluated the in-situ preparation of H₂O₂ and phenol wastewater degradation effect.The use of carbon black（CB）and carbon nanotube（CNT）modified activated carbon fiber（ACF）,carbon felt（CF）and graphite felt（GF）as electrodes was beneficial to increase the concentration of in-situ H₂O₂.Among them,the electro-Fenton system constructed with carbon black modified graphite felt GF（CB）electrode as the cathode and platinum sheet as the anode had the most obvious improvement in H₂O₂ production,at p H=3,the electrode plate spacing is 2 cm,and the aeration amount was 150 m L/min,current density of 7.5 m A/cm²,200 m L of 0.05 mol/L Na₂SO₄ electrolyte,the cumulative concentration of H₂O₂ reacted for 5.5 h was up to 315 mg/L.The electrode material,electrode structure and electrode thickness had a significant impact on the H₂O₂ concentration produced by the electrode.Several modified electrodes with GF（CB）and carbon black modified carbon felt（CF（CB））had a better performance.The thickness of the electrode would affect the internal diffusion of oxygen and the adsorption site of oxygen on the electrode surface.It was an important parameter that affects the production of H₂O₂.The study found that the electrode performance of the GF（CB）electrode with a thickness of 2 mm was the best.SEM analysis found that due to the attachment of CB particles to the GF（CB）electrode,the original macropore structure on the GF surface was modified into a mesopore and micropore structure.The thin layer of CB particles also formed a larger number of micropore structures.After modification,the pore structure was more beneficial to the diffusion and adhesion of O₂and improves the O₂ transfer rate.Using a self-made electrolytic cell,an air cathode reactor was constructed.Under the experimental conditions,when the CF（CB）electrode was an air cathode,the degradation rates of phenol and COD can reach 94.25%and 57.08%,which was higher than that of the traditional electro-Fenton system.The degradation rate increased by25.68%.Nickel foam and modified Fe-C（<0.2 mm）particle catalysts can promote the degradation of phenol and COD,and their degradation rates can reach 99.75%and78.71%,The COD degradation rate was significantly improved compared to the electro-Fenton system without the addition of heterogeneous catalysts.FT-IR and LC-MS analysis tests showed that the intermediate products produced by electro-Fenton oxidation of phenol were mainly pro/hydroquinone,paraquinone,1,2,3-trihydroxyphenol,fumaric/maleic acid,succinic acid,butanetetrol,oxalic acid,etc.,which provided useful information for exploring the phenol degradation pathway of this technology.