Carbon And Nitrogen-based Materials For Removal Of Organic Pollutants In Water By Photocatalytic Degradation/Adsorption

In recent years,with the rapid development of the economy,plenty of industrial wastewater and domestic sewage are discharged into environmental waters.Pollutants in water pose a serious threat to the health of human beings.Thereinto organic pollutants are harmful due to their high toxicity,easy to concentration and degradation-resistant.Therefore,organic pollutants water treatment is a hot topic currently.Among water treatment methods,semiconductor photocatalysis and adsorption have attracted wide attention for their low cost and high removal efficiency.Carbon and nitrogen-based materials include graphitic nitride carbon（CN）and nitrogen-doped carbon materials.CN has been widely used in photocatalysis.Nevertheless,some drawbacks,such as fast electron-hole recombination,low quantum efficiency,and insufficient specific surface area,have largely limited its photocatalytic activity and practical applications.Nitrogen-doped carbon materials.have been used widespreadly in adsorption and separation.Especially,introducing magnetic substances on the surface of porous carbon will facilitate them to separate and recycle use.In this paper,modified CN and porous carbon are applied for the environmental water purification.The research included the following two aspects:1.Pt-doped graphitic nitride carbon（CN-Pt）was used to removal of rhodamine B（RhB）based on the synergy effect of adsorption and photocatalytic degradation.CN-Pt was prepared by thermal polycondensation using dicyandiamide and chloroplatinic acid.The structure and composite of CN-Pt were characterized by scanning electron microscope（SEM）,X-ray diffractometer（XRD）,X-ray photoelectron spectroscopy（XPS）and inductively coupled plasma mass spectrometry（ICP-MS）,which indicated that Pt was successfully doped.The adsorption and photocatalytic degradation properties of CN-Pt for RhB were in detail.Meanwhile,the adsorption thermodynamics and the adsorption kinetics were investigated.It is a monolayer adsorption process that fits the Langmuir model,as well as a spontaneous endothermic process.The maximum adsorption capacity of CN-Pt for RhB is 1.332mg·g^-1.Compared with CN,CN-Pt has a wider light absorption range and a higher photon-generated carrier migration efficiency,which improved the degradation efficiency of CN-Pt for RhB from 50%to 90%.The degradation mechanism of RhB was also studied.Active oxygen species including holes,·OH and ¹O₂ were generated.in the degradation process,and·OH is the main active substance.Synergy effect of adsorption and photocatalytic degradation of CN-Pt greatly improved the removal efficiency of pollutants.Under optimal conditions,the removal efficiency of RhB by CN-Pt was more than 91%.This photocatalytic method has the advantages of simple operation,low cost,and high efficiency and has the potential to remove dyes in wastewater directly by sunlight.2.Rapid removal of triclosan（TCS）and chloroxylenol（PCMX）in water by adsorption on N-doped magnetic porous carbon（Co-NPC）was developed.ZIF-67（Co）was hydrothermally synthesized by 2-methylimidazole and cobalt nitrate.Then,ZIF-67（Co）was carbonized at high temperature in a nitrogen atmosphere to obtain Co-NPC.The materials were characterized by SEM,XPS,Raman spectroscopy,and N₂ adsorption-desorption techniques.The results indicate that Co-NPC remained the crystal structure of ZIF-67（Co）and has a large specific surface area,good pore structure,and excellent magnetism.Besides,we also found Co-NPC was partially graphited.The adsorption performance of Co-NPC for TCS and PCMX was investigated in detail.Compared with undoped porous carbon,Co-NPC significantly improved the adsorption performance for TCS and PCMX.At 298 K,the maximum adsorption capacity of Co-NPC was 163 mg·g^-11 for TCS and 39 mg·g^-11 for PCMX,respectively.The adsorption kinetics and adsorption thermodynamics were further investigated.It was found that TCS and PCMX were fast adsorbed on Co-NPC and reached equilibrium within 3 min.The adsorption processes fit pseudo-second-order model in kinetics and Langmuir isotherm in thermodynamics.These adsorptions are spontaneous endothermic processes with reduced entropy.The adsorption mechanism of Co-NPC was explored by infrared spectroscopy,the amount of hydrogen bond donor and acceptor in molecules.The results demonstrated TCS and PCMX were adsorbed on Co-NPC through electrostatic adsorption,π-πconjugate,and hydrogen bond.This adsorption method has the advantages of simple operation,high adsorption capacity,and recycle-used material.It has a good removal efficiency when it carried out to actual water sample treatment,revealing its potential application for removal of bactericides in wastewater.