The Preparation Of Microfibrous Graphene-based Films Composite Catalyst And Its Application For Catalytic Wet Peroxide Oxidation Of Phenolic Wastewater

The rapid development of modern industry has brought great convenience to people's lives,but at the same time,it has caused serious damage to the environment on which human beings depend,mainly including the pollution of waste water,waste gas and waste residue.Among them,phenol-containing wastewater?such as phenol?has the characteristics of wide sources,high toxicity,and difficulty in degradation,so it is particularly urgent to effectively treat it.At present,the common treatment methods of phenol-containing wastewater include physical separation method,biodegradation method and chemical treatment method.Among them,the catalytic wet peroxide oxidation?CWPO?method in the chemical treatment method is widely used in the treatment of phenol-containing wastewater due to the advantages of mild conditions,wide processing concentration,and fast and efficient reactions.The key of CWPO technoque is to find a suitable catalyst.At present,a large amount of research on CWPO of phenol-containing wastewater has focused on metal catalysts.Metal catalysts can exhibit excellent catalytic activity in CWPO of phenol,but it will inevitably leach out the metal active components during the reaction process,leading to the secondary pollution.Therefore,developing an efficient and stable graphene-based catalyst and designing a technology for CWPO of phenol-containing wastewater is an important topic with theoretical significance and practical value.Based on the research of paper-like stainless steel microfibers?PSSF?as a catalyst carrier,a series of porous microfiber composite graphene-based catalysts for the treatment of phenol-containing wastewater have been developed.The catalytic performance,catalytic stability,reaction mechanism and deactivation mechanism of phenol and intrinsic kinetics of catalytic oxidation are studied.First,the CWPO of phenol over PSSF-Gr catalyst in a fixed-bed reactor was studied.Through CVD methods,PSSF-Gr catalysts with different graphene thicknesses were successfully prepared by adjusting the flow rate,deposition time,and deposition temperature of C₂H₂.Through a series of modern characterization techniques,it was proved that the synthesized graphene film was tightly covered on the surface of PSSF support and the catalyst still maintained the three-dimensional network structure.The PSSF-Gr catalyst with single-layer graphene performed the best catalytic activity in a fixed-bed reactor for CWPO of phenol:the phenol conversion was 99%,and the TOC conversion was 73%.The catalytic activity of PSSF-Gr was attributed to the metal-free Gr catalyst,and its catalytic mechanism was the mechanism of·OH.The catalyst showed good stability in a fixed-bed reactor.After 72 h of continuous reaction,the catalyst still had high catalytic activity.As the catalytic reaction continued to 96 h,the catalyst showed significant deactivation.The main reasons for the inactivation were the changes in the surface chemistry and structure of graphene,adsorption of phenol and catechol,and corrosion and collapse of the three-dimensional network structure.Secondly,the CWPO of phenol over PSSF-Gr-NCNT catalyst in a fixed-bed reactor was studied.By CVD methods,the PSSF-Gr-NCNT composite catalyst was successfully prepared by adjusting the order of opening the heating pack,the position of the plug,the flow rate of N₂,the flow rate of C₂H₂,the amount of melamine and deposition temperature.Through a series of modern characterization techniques,it was proved that the synthesized graphene film was tightly attached to the PSSF support,and the N-doped carbon nanotubes were grown on the surface of the graphene film and the gap of three-dimensional network structure.The N/C atomic percentage of the PSSF-Gr-NCNT catalyst prepared under optimal conditions was 4.4%.The graphene on the PSSF-Gr-NCNT catalyst was seven-layer N-doped graphene,and the carbon nanotubes were N-doped multiwalled carbon nanotubes.In a continuous fixed-bed reactor for CWPO of phenol,the phenol conversion rate of PSSF-Gr-NCNT reached 100%and the TOC conversion was up to 43%.The catalytic activity of PSSF-Gr-NCNT catalyst was slightly higher than that of PSSF-Gr catalyst with the same graphene thickness,and the main reason was that the N doping of carbon nanotubes and graphene increased the electron transfer of the catalyst.The catalytic mechanism of the PSSF-Gr-NCNT catalyst was also the·OH mechanism.Thirdly,the CWPO of phenol over PSSF-NGr catalyst in a fixed-bed reactor was studied.By CVD methods,PSSF-NGr catalyst was successfully prepared by adjusting the N₂ flow rate,H₂ flow rate,the amount of melamine and deposition temperature.Through a series of modern characterization techniques,it was proved that the synthesized N-doped graphene film was tightly attached to the PSSF support and still maintains the three-dimensional network structure of the PSSF support.By studying the catalytic activity of PSSF-NGr under all preparation conditions,it was found that the thickness of NGr and the type and content of doped N on PSSF-NGr affect the catalytic performance.The PSSF-NGr catalyst which had lower NGr layers,high ratio of graphite-N,and high content of N/C performed higher catalytic activity,and the phenol conversion was 100%and TOC conversion was up to 62%.The catalytic mechanism of PSSF-NGr catalyst was also the·OH mechanism.Finally,the intrinsic kinetics of CWPO of phenol using a porous microfiber and graphene composite catalyst on a fixed-bed reactor was studied.The effects of the thickness of the graphene film and the feed flow rate on the phenol conversion were investigated to eliminate the internal and external diffusion in the catalytic reaction.The kinetic data of phenol catalytic oxidation was fitted using Power-rata Law kinetic model.The results showed that the CWPO of phenol using PSSF-Gr catalyst on a fixed-bed reactor was a first-order reaction.The reaction activation energy is 106.06 k J mol^-1.