Study On The Treatment Of Dye Wastewater With Modified Graphite Felt Cathode In Three Dimensional Electrode Fenton Reactor

The pollution of dye wastewater is extremely serious due to its poor biochemical properties and high colour content,which contains a variety of harmful organic pollutants,and the complexity of the composition of these pollutants makes the problem of dye wastewater pollution extremely serious.In addition,the dyestuffs in dye wastewater are becoming more stable and less easily degraded as technology advances,and the pollution discharge standards for dye wastewater are becoming increasingly stringent.The three-dimensional electrode electro-Fenton technology is a combination of three-dimensional electrode and electro-Fenton technology,which can achieve a variety of electrochemical oxidation processes,including direct anodic oxidation,particle electrode adsorption,cathodic aeration reduction to generate H₂O₂ and Fenton reagent reaction,so as to achieve the purpose of purifying water bodies.In this paper,a three-dimensional electrode electro-Fenton system was constructed to treat Rhodamine B wastewater using a home-made modified graphite felt as the cathode.By comparing the differences of graphite felt（GF）cathodes prepared by different doping modification methods,the optimal modified graphite felt was selected,and the treatment effects of different systems for Rhodamine B wastewater were compared to explore the superiority of the three-dimensional electrode electric Fenton system.The operating parameters of the three-dimensional electrode electro-Fenton system were optimised by single-factor experiments and response surface method.Finally,bursting experiments were carried out to verify the main reactive radicals,the degradation effect of the system and the kinetics of·OH generation were analysed to investigate the degradation process of Rhodamine B.The degradation process was further investigated by means of 3D fluorescence spectroscopy and UV-visible spectroscopy.（1）Three graphite felts with single metal and co-doped metal were prepared by ultrasonic impregnation with manganese sulfate monohydrate and copper nitrate trihydrate,and the surface morphology,functional groups and hydrophilicity of the modified graphite felts were characterized by SEM,FT-IR and contact angle.The hydrophilicity was enhanced and the surface loadings were more dense and abundant,thus providing more active sites and enhancing the degradation effect.（2）By examining the performance of different cathode materials in H₂O₂ production and wastewater degradation,it was found that the H₂O₂ concentration produced by GF-3was greater than the other three cathode materials,and the removal efficiency of COD and Rhodamine B by GF-3 was increased by 40.5%and 33.2%respectively compared with that of GF-0.Comparing the treatment effects of the four processes of three-dimensional electrode electrofenton,three-dimensional electrolysis,two-dimensional electrolysis and Fenton on Rhodamine B wastewater,the results showed that after 120min of reaction,the three-dimensional electrode electrofenton system had the best treatment effect,and the removal rates of COD and Rhodamine B were 83.3%and 96.4%,respectively.（3）The single-factor current density,initial p H,Fe²⁺concentration,electrolyte concentration and aeration amount were investigated on the degradation effect of Rhodamine B wastewater,which showed that current density,reaction time and initial p H were important factors affecting the removal rate of COD and Rhodamine B.The response surface optimization experiment proved that current density,reaction time and initial p H all had significant effects on the removal rate of COD,and the order of effects The order of influence is:reaction time>current density>initial p H;for Rhodamine B removal,the order of influence is:current density>initial p H>reaction time.The optimum process parameters were predicted to be 17.37m A/cm² current density,136.45min reaction time and 3.95 initial p H.Under these conditions,the maximum removal efficiency of COD was 83.25%and the maximum removal rate of Rhodamine B was 91.90%.（4）The free radical burst experiments showed that the hydroxyl radicals,direct oxidation and adsorption on the particle electrode surface and anodic oxidation acted synergistically to degrade Rhodamine B.Moreover,the degradation process of Rhodamine B was in accordance with the secondary kinetics and the·OH generation was in accordance with the zero-level reaction kinetics.Five characteristic absorption peaks of Rhodamine B simulated wastewater were found by 3D fluorescence spectroscopy,which disappeared at the end of the reaction,indicating that Rhodamine B was effectively removed during the reaction process.The UV-visible spectrogram shows that the characteristic absorption peaks at 554 nm and 260 nm become small at the end of the reaction,indicating that the colour-emitting group and aromatic ring structure of the Rhodamine B molecule are broken;the absorption peak at 554 nm is blue-shifted,indicating that the ethyl group on the branched chain of the Rhodamine B molecule is removed and intermediate products are produced,the characteristic absorption peak at260 nm has a less obvious trend to decrease,indicating that the aromatic structure The presence of other absorption peaks indicates that there are still difficult to degrade substances present in the solution.