Activation Of Persulfate Over Modified Porous Carbon For The Degradation Of Organic Pollutants:A Mechanism Study

Advanced oxidation processes based on persulfate（PS-AOPs）are widely used in the treatment of refractory organics in water due to their fast reaction rate,strong oxidation performance and mild reaction conditions.Porous carbon materials can effectively activate persulfate,but the catalytic efficiency is usually low,and catalytic sites and mechanism of persulfate activation is still unclear.In this paper,porous carbon was modified by doping nitrogen and iron/nitrogen to improve the reaction efficiency to degrade organic matter.By studying the structure-activity relationship and key factors influencing the degradation of bisphenol A（BPA）,the active sites and mechanisms of PDS activation over the modified carbon were investigated.The main research and conclusions of the thesis are as follows:（1）Nitrogen-doped porous carbon materials（N-MCs）were prepared by using low-cost plant polyphenol（e.g.,tannic acid）as the carbon source.The synthesis conditions of N-MCs were optimized.Scanning electron microscopy（SEM）and transmission electron microscopy（TEM）showed that N-MCs displayed spherical morphology with high specific surface area and abundant porous structure.XPS analysis showed that nitrogen atoms were successfully doped into the skeleton structure of N-MCs,and calcination temperature was the main factor affecting the composition and surface functional groups of N-MCs.The results of organic catalytic experiments showed that the doping of heteroatom nitrogen significantly improved the catalytic activity of porous carbon.Nitrogen-doped porous carbon N-MCs-800 effectively activated PDS to degrade emerging organic pollutants like BPA.The degradation of BPA followed first-order reaction kinetics with a reaction rate of 0.07 min^-1.Organic pollutants were mainly degraded via the electron transfer regime.Therefore,inorganic anions(such as Cl^-,CO₃^2-,SO₄^2-and NO₃^-)in water exhibited limited influence on BPA removal.（2）In order to further improve the electron transport efficiency of nitrogen-doped porous carbon,iron-nitrogen co-doped mesoporous carbon（Fe/N-MCs-900）was prepared.SEM,TEM and XRD analysis showed that Fe/N-MCs displayed spherical structure,and Fe and N elements were homogeneously distributed throughout the Fe/N-MCs nanospheres.The calcination temperature was the key factor affecting the microstructure and surface properties of Fe/N-MCs.Fe/N-MCs-900 had the largest specific surface area and the highest degree of defects.Fe/N-MCs-900 had both adsorption and catalytic properties.The adsorption of BPA reached saturation within 30min.When 0.2 mM PDS was added,BPA was completely removed within 15 min with a rate constant of 0.22 min^-1.Chemical quenching experiments,electron paramagnetic resonance（EPR）test,electrochemical analysis and Raman tests revealed that the Fe/N-MCs-900+PDS system oxidized organic matter through a non-radical pathway based on electron transfer process.And inorganic ions and natural organic matter exhibited limited influence on the oxidation efficiency.XPS analysis revealed that the active sites of Fe/N-MCs-900 were mainly graphite-N,C-OH and FeC₃nanoparticles.The co-doping of Fe and N increased the defect degree of porous carbon catalyst,greatly enhanced the activation of PDS and degradation organic pollutants.