| Electro-Fenton technology occupies a major position in wastewater treatment due to the characters of mild reaction conditions,fast reaction rate,and continual hydroxyl radicals produced.However,there are problems such as narrow p H range,poor conductivity of cathode materials,and iron sludge formation during the process.In order to overcome the shortcomings of electro-Fenton,the cathode was prepared by nitric acid modified needle coke,combined with the DSA anode to form an electro-Fenton system to treat Rh B and coking wastewater in this project.The purpose was to provide a certain experimental basis and theoretical basis for the application of the self-developed needle coke composite electrode.Needle coke with good conductivity was used as experimental raw materials and modified by nitric acid to prepare the needle coke composite electrode.The structure and surface morphology of the electrode were analyzed and characterized by SEM,EDS,XRD,FT-IR spectroscopy and BET methods.The results showed that iron was successfully supported in the electrode which had a rich porous structure.After the needle coke was modified by nitric acid with a concentration of 40%,the surface carboxyl,hydroxyl and other oxygen-containing functional groups increased.The degree of graphitization of needle coke was increased and the conductivity was further increased.Electro-Fenton system was constructed of needle coke composite electrode cathode and DSA anode to treat Rh B.The electrode prepared by nitric acid modified needle coke with a good effect on Rh B degradation.The electrode prepared under the optimized condition,the decolorization rate of Rh B could reach 100%while the COD removal rate could reach 81.2%.According to UV-Vis analysis,Rh B was gradually oxidized,opened and destroyed as the reaction time increased.·OH quenching experiment revealed that the novel needle coke composite cathode electro-Fenton system produced·OH,which played a major role in the Rh B degradation.Electro-Fenton system was composed of needle coke composite electrode cathode and DSA anode to treat coking wastewater.The BBD response surface experiment was designed,and then a second-order regression models between the voltage,initial p H value,and electrode spacing as the factors and the COD removal rate,NH3-N removal rate,and TOC removal rate as the response value were established.The models were checked to investigate the influence of various factors and their interaction on the response target,and finally the electro-Fenton conditions in coking wastewater treatment were optimized.The results showed that the regression models are significant.The optimal COD removal rate achieved 89.96%under the conditions of applied voltage of 4.92V,electrode spacing of 2.29cm,and initial p H value of 3.01;the optimal TOC removal rate achieves 73.44%under the conditions of applied voltage of 4.83V,electrode spacing of 1.06cm,and initial p H value of 3.29;while the optimal NH3-N removal rate achieves 84.12%under the conditions of applied voltage of 4.99V,electrode spacing of 1.11cm,and initial p H value of 3.00.Furtherly,the degradation mechanism of organic pollutants in treating treatment coking wastewater with the electro-Fenton method was investigated,and conduct energy efficiency was analyzed.According to GC-MS and FT-IR analysis,needle coke composite electrode cathode produced·OH to deoxidize and decompose Phenols,quinolines,PAHs,and oxygen-containing and nitrogen-containing heterocyclic compounds in coking wastewater.COD degradation followed quasi-first order reaction kinetics.The unit energy consumption was 0.03k Wh·g-1COD-1 and0.047k Wh·L-1 coking wastewater.The self-developed needle coke composite electrode has good conductivity,reusability,and stable structure,which combined with the DSA anode to form an electro-Fenton system to effectively remove Rh B and pollutants in coking wastewater.In addition,there is no need to add H2O2 or iron salt in the reaction,no iron sludge is formed,which has a good industrial application prospect. |
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