Nitrogen-doped Carbon Material Activates Persulfate To Degrade Phenolic Organic Pollutants In Water

Phenolic contaminants are considered to be the most common organic pollutants in wastewater from agricultural and industrial sources.Advanced oxidation treatment of phenolic wastewater has the advantages of fast processing speed and good mineralization.This thesis mainly uses the self-developed nitrogen-doped carbon material to activate persulfate to degrade phenol and phenol derivatives.In this study,the nitrogen-doped carbon material catalyst utilizes the cheap and readily available waste industrial syrup as a carbon source,and ammonia as the nitrogen source.The aluminum phosphate skeleton is used as the template by the sol-gel method,and the new nitrogen-doped carbon materials?NC-800,GNC-800?are prepared by calcination.The characteristics of the material were described by a series of characterization methods.The results show that the mico-surface roughness of the nitrogen-doped carbon material has no fixed shape which belongs to weakly graphitized microcrystalline carbon.After secondary calcination,more defects are formed on the surface,and the specific surface area,pore size and pore volume of the material are increases Fourier transform infrared spectroscopy?FTIR?and X-ray photoelectron spectroscopy?XPS?show that nitrogen is successfully doped into the carbon skeleton.In addition,the XPS results also show that the oxygen and nitrogen elements are reduced due to the decomposition of oxygen-containing functional groups and C-N bonds at high temperatures.The content of N-5 in GNC-800 is lower than the NC-800,but the content of the N-Q and N-6 in GNC-800 is higher than that the NC-800.Through the control experiment,the nitrogen-doped carbon material can effectively activate the persulfate to degrade phenol.The new nitrogen-doped material GNC-800?50 mg/l?can effectively activate PDS?1 mM?to catalyze the degradation of phenol?0.1 mM?at 25?.In 15minutes,the degradation rate of phenol is almost 100%?below the instrument detection limit?,and the reaction is suitable for pseudo first-order kinetics.Compared with NC-800 material,GNC-800 shows higher catalytic removal efficiency with rate constant of 0.058 min^-11 and0.211 min^-1,respectively.The catalyst system?GNC-800/PDS?has a wide pH range and can effectively remove phenol in the pH range of3-9.Higher PDS concentrations and GNC-800 doses result in higher phenol degradation efficiencies.In addition to phenol,the GNC-800/PDS system also shows good removal of other phenolic compounds?including4-chlorophenol,2,4-dichlorophenol,p-nitrophenol,and so on?.The results of the free radical masking experiment show that the phenol degradation was not greatly affected in the presence of radical scavengers?methanol,ethanol and ter-butanol?.However,in the presence of singlet oxygen quencher?FFA and NaN₃?,the degradation rate of phenol is significantly reduced.Further,through ESR experiments,it is proved that the active substance of oxidized phenol is singlet oxygen.The degradation of phenol by the GNC-800/PDS system follows the non-radical pathway by which singlet oxygen acts on contaminants.In addition,comparing the nitrogen-containing functional group content of the original material and the re-used material with the experimental results of the material-activated persulfate-degrading phenol and related literature studies,it is concluded that different nitrogen functional groups play a key role in the catalytic oxidation of phenol,especially pyridine nitrogen and graphite nitrogen.