Degradation Of Dimethyl Phthalate By Electro-Fenton Cathode Modified With Carbon-based Materials And Its Mechanis

Phthalates（PAEs）have been widely used in industrial production to soften rigid plastics（plasticizers）,and their related products are widely distributed in our daily lives.Meanwhile,PAEs are endocrine disruptors that disrupt normal hormonal responses,leading to developmental and reproductive problems.As a kind of advanced oxidation technology（AOPs）,electro-Fenton technology has the advantages of rapid reaction,complete degradation,and effectively avoiding the risk of H₂O₂ transportation and storage.In the electro-Fenton degradation system,the production of H₂O₂ by the cathode oxygen reduction reaction and the reduction of 3-valent iron ions are the rate-controlling steps.Usually,noble metals are used as catalysts for cathodes,but the high price of noble metals and the scarcity of storage capacity limit their popularization and use.In view of the above problems,this paper selects carbon materials with high specific surface area and lots of defect sites as the research object,in order to prepare catalysts with high electrocatalytic activity and good stability.In this paper,two carbon material substrates were synthesized using melamine as a soft template and distiller’s grains as a biomass carbon precursor,and then transition metal cobalt and Fe₃O₄ nanoparticles were doped into the corresponding carbon material substrates through a series of treatments.And by characterizing the morphology and structure of the material,the electrocatalytic oxygen reduction performance of the material was tested.Finally,dimethyl phthalate（DMP）was used as the target pollutant to test the degradation efficiency and optimize the reaction conditions.The main findings of the study are as follows:（1）Under the condition of using melamine as a soft template,Co was doped into it and calcined at high temperature to form a two-dimensional single-atom catalyst.The material contains four elements Co,N,S and C.Through the characterization of Co@NSC,it is found that the material belongs to the mesoporous structure,the main pore size distribution is between 1.3-16 nm,the specific surface area and pore volume are 223.26 m²/g and 0.392 cm³/g,respectively.In the electrochemical performance test,with or without cobalt doping as a variable,the results show that the two-electron oxygen reduction ability of the material can be effectively improved in the case of cobalt doping.Using Co@NSC as an electro-Fenton cathode to degrade DMP can be completely removed within 30 min,with excellent degradation efficiency and TOC mineralization rate（38.9%）even under neutral and alkaline conditions.In the exploration of the mechanism,it was found that·OH and ¹O₂ were the main contributors.According to DFT theoretical calculation and LC-MS results,the vulnerable site and degradation path of DMP were reasonably speculated.The ecotoxicity evaluation of the degradation products showed that the Co@NSC electro-Fenton system showed a significant ability to reduce the toxicity of DMP degradation.Co@NSC can not only reduce the amount of metal used to reduce the cost,but also fully utilize metal sites,which is a cost-effective and very promising option.（2）Using waste distiller’s grains as biomass carbon precursor,the composite material（Fe₃O₄@NOPC）supported by nitrogen and oxygen co-doped biomass carbon was prepared by carbonization,hydrothermal and thermal reduction.The results show that using biomass carbon as a carrier,its porous structure and abundant surface functional groups can accelerate the mass transfer of intermediates,and when the ratio of Fe³⁺to Fe²⁺doped is 2:1,it has better degradation efficiency.In the case of iron source,70%of pollutants can be removed in 5 hours.The proper ratio can speed up the conversion of Fe³⁺to Fe²⁺.In the exploration of the degradation mechanism,it was found that in addition to the·OH radical,there was also a part of the combined action of electro-oxidation and adsorption.In the first electro-Fenton reaction,the loaded Fe₃O₄ nanoparticles can act as an iron source,and in the subsequent cycle experiments,it can also greatly reduce the dosage of iron ions,reduce the production of iron-containing sludge,and avoid secondary pollution.This provides a new idea for reducing the cost of electro-Fenton and effectively utilizing waste resources and reducing sludge production.