Preparation Of Carbon-based Catalysts And Their Performance Of Activating Persulfate For Degradation Of Aromatic Pollutants

Sulfate radical-based advanced oxidation processes(SR-AOPs)became one of the most promising new technologies for degrading organic pollutants,which could produce highly reactive free radicals in a wide pH range.As the oxidant in SR-AOPs,however,persulfate is very stable under ambient conditions,which could only be activated to produce highly oxidative species via external excitation or catalysis.In comparison with homogeneous catalysts or metal oxide catalysts,carbonaneous materials could effectively avoid secondary pollution.Hence,carbocatalyst has been considered as one of the most promising catalysts for green remediation technologies.In SR-AOPs,the active sites of carbonaneous materials are closely correlated with heteroatomic doping,sp2 hybridization structure,defect site concentration and surface functional groups.The objective of this study was to design carbonaneous catalyst with special structure and active sites to improve the catalytic performance.The catalytic activity was evaluated by degradation of four aromatic contaminants(i.e.,phenol,o-phenylphenol,Bisphenol F,naproxen),and combined with characterization results to further investigate the correlationships between structure and composition and catalytic activity of carbon catalysts.The main results are as follows:1.N-doped mesoporous carbon(NMC)catalysts were prepared by the hard template methods.The N content and N species in NMC catalysts were adjusted by controlling the nitrogen precursors and carbonization temperatures.The catalytic activity of NMC catalysts was evaluated by activating PMS for OPP degradation.The characterization results presented that increasing carbonization temperature could decrease the nitrogen content and increase the proportion of graphite nitrogen.The NMC catalysts with high special surface area and ordered pore structure exhibited efficiently of PMS catalytic activity.The catalytic activity of NMC presented a volcano-type dependence with increasing carbonization temperatures from 70? to 1000?,which was closely correlated with the content of pyridine nitrogen and graphite nitrogen.The research results were helpful to design nitrogen doped carbon materials with efficient nitrogen atom utilization.2.As a cobalt containing macrocyclic compound,vitamin B12 was used as a precursor to prepared cobalt doped CoCNx@SBA-15 catalyst by incipient wetness impreganation.For comparison,CoCNx/SBA-15 and CoCNx/SiO2 were prepared using the conventional impregnation method.The catalytic activitives of the prepared catalysts were investigated via activating PMS to degrade NPX.The characterization results showed that the CoCNx active sites in CoCNx@SBA-15 catalyst were mainly confined in the channels of SBA-15 rather than on the surface.Due to the synergistic effect between cobalt species and CNx in the confined space,CoCNx@SBA-15 possessed the highest catalytic activity even higher than the homogeneous catalytic system Co2+/PMS.The confined catalyst CoCNx@SBA-15 could sustentially inhibit the leaching of cobalt species.3.N-doped carbon quantum dots(NCQDs)with graphite structure were synthesized using fumaronitrile as the precursor by the hydrothermal method.The supported NCQDs catalysts were obtained via impregnating NCQDs on supports with different isoelectric points(IEPs),i.e.,NCQD/Al2O3?NCQD/SiO2 and NCQD/CeZrO2.The catalytic activitives of the supported NCQDs catalysts were evaluated by activating PDS to degrade Bisphenol F(BPF).The characterization results exhibited that the IEPs of NCQD/SiO2,NCQD/CeZrO2 and NCQD/Al2O3 were<2.0,5.8 and 7.6,respectively.The NCQDs were uniformly distributed on Al2O3(IEP=8.1)and CeZrO2(IEP=6.2)which had higher IEPs.The difference of surface charge led to difference electrostatic interaction between catalysts and persulfate anions(S2O82-),which was further affected the catalytic activity.Under the neutral condition,the surface of NCQD/Al2O3 was positive charge and existed electrostatic attraction between S2O82-,and NCQD/Al2O3 presented higher catalytic activity than NCQD/SiO2 and NCQD/CeZrO2.The initial activity of NCQD/Al2O3 existed a volcano-type dependence with increasing the NCQDs loading amount.Upon normalized by NCQDs loading amount,the initial activity decreased with increasing NCQDs loading amount,ascribed to low exposure of active sites.Additionally,the activation of PDS on the surface of catalyst was in line with Langmuir-Hinshelwood model,further reflecting that the activation of adsorbed PDS was the rate controlling step.4.The carbon based catalysts deactivated in SR-AOPs.In the study,CNT and NCNT with stable structures were used as model catalysts to investigate the mechanism of surface functional groups in the process of catalyst deactivation and regeneration.CNT and NCNT with different cycle times were prepared,and their catalytic activity significantly decreased with the increase of the acidic oxygen-functional groups and decrease of PZCs.The deactivated CNT and NCNT were regenerated by thermal reduction and chemical reagent reduction.The catalytic activity of regenerated CNT and NCNT increased,and was depended on regeneration methods.As for regenerated CNT catalysts,the catalytic activity enhanced with the treatment thermal temperature,and even higher than the fresh CNT catalyst.For NCNT catalysts,the catalytic activity could only partially restored.The study of deactivation and regeneration mechanism contributed to the practical application of carbon-based catalysts in SR-AOPs.