Degradation Of Methyl Orange Wastewater By Electr-Fenton Process

The electro Fenton oxidation technology has the characteristics of rapid,thorough and efficient,and is widely applied in the field of wastewater treatment,especially in dyestuff degradation.At present,the technology is mainly restricted by factors such as low efficiency of electrogenerateing H₂O₂ and difficult recycling of catalyst.From this point of view,a porous hydrophobic cathode was designed and prepared,which greatly increased the yield of H₂O₂.Moreover,Fe₃O₄ nanoparticles were loaded on activated carbon via coprecipitation.The obtained composite catalyst not only realize magnetic recyclability,but also could adsorb and enrich organic matters,enhancing the catalytic efficiency.Porous hydrophobic cathodes were prepared using acetylene black and polytetrafluoroethylene?PTFE?by coating.The scanning electron microscope?SEM?photographs showed that the active substance is a three-dimensional structure with PTFE as the skeleton,and there are many holes which can provide space for the transmission and storage of O₂.It was found that the yield of H₂O₂was not limited by dissolved oxygen,and the voltage was not affected by gas flow.The current efficiency of electrogenerating H₂O₂ was close to 100%,and the cumulative concentration increased linearly with the increase of current density and electrolysis time.When the electrode was applied to homogeneous electro-Fenton process,the solution was completely decolorization after electrolyzing for 20 min with pH at 3,the cathode current density 300 mA/cm²,the initial concentration of methyl orange?MO?100 mg/L,the dosage of Fe²⁺0.4mmol/L,and the Na₂SO₄ of the conductive salt 0.1 mol/L.The use of porous hydrophobic cathode not only shortened the electrolysis time,but also reduced the dosage of catalyst.Fe₃O₄ nanoparticles were prepared via coprecipitation,and their phase size was analyzed by X ray diffraction?XRD?and SEM respectively.The results show that the particle size is about 40 nm with high purity.The effects of initial concentration of MO,catalyst dosage,pH,reaction temperature and cathodic current density on the degradation of MO by heterogeneous Fenton were studied.The results show that when the initial concentration of MO is lower than 30 mg/L,the removal rate of MO is more than 99.8%after electrolyzing for 40 min with the cathode current density 10 mA/cm²,pH=3 and Fe₃O₄ dosage 50 mg/L.According to atomic absorption analysis,the concentration of dissolved iron ion was below 2 ppm which proved the high stability of the catalyst.Then,the same Fe₃O₄ particles were loaded onto the activated carbon to prepare the composite catalyst.Using the composite,MO could be degraded more rapidly.The theoretical calculation of the maximum immersion depth of porous cathode was also carried out,and the results were verified by experiments.When studying the kinetics of heterogeneous MO degradation of Fenton,we found that its degradation behavior was pseudo first order kinetics.