Mn,Ce Co-Doped G-C₃N₄ Activated Peroxymonosulfate For Degradation Of 2,4-Dichlorophenol In Water

Chlorophenols are important organic chemical raw materials,which have been used in large quantities for a long time,making them enter the water environment in various ways,and widely exist in wastewater,surface water,and groundwater,causing water pollution.2,4-dichlorophenol（2,4-DCP）,one of the typical chlorophenols,has been frequently detected in water bodies,and its strong toxicity seriously threatens human health and safety.However,it is difficult for traditional water treatment technology to degrade it effectively.As an emerging technology,persulfate-based advanced oxidation processes（AOPs）have been widely used for the removal of refractory organic pollutants in water due to its strong oxidizing ability,non-selective degradation,and wide range of applicable environmental pH.At present,the key to the application of this technology is to seek efficient catalysts with simple preparation,strong stability,and low cost.Graphitic carbon nitride（g-C₃N₄）,as an inexpensive and readily available conjugated polymer,has received close attention from researchers in recent years and has been gradually applied to peroxymonosulfate（PMS）activation.However,the catalytic efficiency of pure g-C₃N₄ is generally low,and it is generally necessary to further improve its catalytic efficiency by introducing metals.At present,some single-metal doped g-C₃N₄ is used for PMS activation,but there are problems of large amount of metal doping and high cost.Therefore,in this study,a new Mn,Ce co-doped g-C₃N₄（MnCe-CN）catalyst was successfully prepared by a one-step calcination method using cerium chloride heptahydrate,manganese chloride tetrahydrate,formic acid,and urea as raw materials.The catalyst was then used to activate PMS to degrade organic pollutants,and its basic characteristics and catalytic performance were evaluated.（1）The MnCe-CN catalyst was analyzed by XRD,SEM,TEM,FTIR,and XPS,which showed that Mn and Ce were uniformly distributed in g-C₃N₄,and existed in the form of Mn-N structure and CeO₂,respectively.（2）The MnCe-CN/PMS system could effectively degrade 2,4-DCP and was less affected by initial solution pH.The 2,4-DCP could be completely degraded within 30min and its degradation process followed pseudo-first-order kinetics,when the initial concentration of 2,4-DCP was 20 mg/L,the dose of MnCe-CN was 0.5 g/L,and the concentration of PMS was 0.8 mM.（3）Based on the detection results of GC-MS,two main degradation pathways of2,4-DCP in the MnCe-CN/PMS system were speculated,and finally 2,4-DCP was degraded into small molecular compounds.（4）According to the active species masking experiment,electrochemical characterization,and EPR detection analysis,superoxide radical(O₂^·-),singlet oxygen（¹O₂）,and electron transfer pathways work together to degrade 2,4-DCP in MnCe-CN/PMS system.（5）The MnCe-CN composite had low metal leaching and good recyclability,and it could achieve 85%degradation of 2,4-DCP after being reused for 4 times.In actual water samples,the MnCe-CN catalyst can degrade more than 90%of 2,4-DCP,which has good practical application potential.