Synthesis Of Nitrogen-Doped Hierarchically Porous Carbon As Catalyst For The Degradation Of Organic Pollutants

Water pollution caused by reckless industry discharge is becoming more and more serious all over the world,which is a serious environmental problem to be solved.In recent years,with the development of advanced oxidation processes（AOPs）,the peroxymonosulfate（PMS）-based AOPs have attracted great attentions.Compared with the Fenton reaction,PMS possess a higher oxidation potential capacity.Moreover,it can be effectively applied in a wide p H range from acidic to alkaline solutions.So it is more appropriate for water treatment.In this reaction,the role of the catalysts is very important.Although metal-based catalysts have strong catalytic activity,they still suffer from inevitable metal leaching and secondary pollution.Therefore,it is of great significance to develop a non-metallic catalyst with simple preparation,low cost and high catalytic performance for the practical application of the PMS activation.To address the above problems,nitrogen-doped and hierarchically porous carbons with ultrahigh specific surface areas are fabricated using NaNO₃as a template.And the applicability of this method to different carbon and nitrogen sources was explored.In addition,the effect of different conditions on the activation of PMS and its reaction mechanism were studied,which provided theoretical basis for practical application.Firstly,hierarchically porous carbons were fabricated using NaNO₃as a template and glucose as carbon precursors.Then the samples were treated with NH₃ at high temperature to obtain nitrogen doped porous carbons,which were labeled as NC-X-T（X refers to the weight ratio of NaNO₃and glucose,and T refers to the annealing temperature）.Taking phenol as the model pollutants,the effects of different experimental conditions on the catalytic performance were studied.The experimental results show that the process of pore forming and nitrogen doping can obtain strong catalytic capacity.The reaction rate constant of NC-0.5-800 is 0.397min^-1,which is superior to most metal and non-metal catalysts.And the activation energy of this system is 10.15 k J/mol,lower than other catalysts/PMS system,which is more favorable for PMS activation.On this basis,considering the material structure and practical application,polyacrylamide（PAM）was selected as carbon and nitrogen source,and hierarchically porous carbons with ultrahigh specific surface areas(>4000 m²g^-1)was synthesized in situ by one-step carbonization.The materials demonstrates an outstanding catalytic activity to degrade phenol with a rate constant of 0.622 min^-1.The ultrahigh catalytic activity of the carbocatalysts results from the large SSA,nitrogen modification,abundance of defective sites,and functional groups.The mechanism investigation shows that the PMS activation pathway could be transformed from a radical dominated process into a nonradical pathway due to the formation of massive defective edges in the porous structure.In the third part of this thesis,we investigated the effect of the prepared catalyst/PMS system on the treatment of actual dyeing wastewater.After flocculation and catalytic oxidation treatment,the COD of the wastewater decreased from the initial8783 mg/L to 98 mg/L,which satisfied the National Standard for Wastewater Discharge.This result confirmed that the system can effectively treat the actual dyeing wastewater.In addition,we prepared a series of heteroatom doped porous carbon materials by NaNO₃salt-templating method with different biomass as precursors,all of which have excellent catalytic performance,indicating that the preparation method has a wide applicability.In summary,NaNO₃salt-templating method is simple,low-cost,and very versatile for different carbon and nitrogen sources,which has a great potential for the practical production of low-cost,high-performance,and functional carbon materials for wastewater treatment.