| With the continuous deterioration of the global water environment and the increasing pollution of dye wastewater,photo-Fenton catalytic technology is widely used in the field of dye wastewater treatment with its unique advantages.In this paper,waste bamboo chips are used as raw materials,and bamboo fiber is extracted by chemical method.Then,the bamboo fiber extraction rate is the target parameter,and the process conditions are optimized through orthogonal experiments.The bamboo fibers extracted under the optimal process conditions are selected and carbonized to obtain carbon fibers.(CF).Then,the surface of CF was modified with polydopamine(PDA),and nano-Fe3O4 and nano-TiO2 were hydrothermally loaded to successfully prepare a magnetically recyclable photo-Fenton catalyst with bamboo fiber as a template.The performance was compared after calcination in air atmosphere..Taking the degradation rate of methylene blue(MB)solution as the response value,the preparation process of the photo-Fenton.catalyst was optimized by response surface experiment,and the photo-Fenton catalyst prepared under the optimal process conditions was selected to explore its reaction mechanism.The microscopic morphology,phase structure,chemical elements and magnetic responsiveness of the photo-Fenton catalyst were characterized by SEM,XRD,XPS,and VSM,respectively,and the pore structure was characterized by pore size analysis.Finally,the prepared photo-Fenton catalyst was applied in large quantities in the treatment of dye wastewater in sewage treatment plant,and the photo-Fenton catalytic degradation tank was designed into the process flow of sewage treatment plant,and the degradation of dye wastewater by different amounts of catalyst and H2O2 was investigated.The main research conclusions are as follows:(1)The extraction process of bamboo fiber was optimized by orthogonal experiments,and range analysis and variance analysis were used to determine the influence of each factor on the extraction rate of bamboo fiber in the order of reagent concentration>reaction temperature>reaction time.The reagent concentration was the main factor,while the reaction time and reaction time Temperature is a secondary factor.The highest yield of bamboo fiber extracted by nitric acid was 8 mol/L,2 h,60℃,and the yield of bamboo fiber was 34%,but it was lower than the highest yield of bamboo fiber extracted by sodium hydroxide,that is,6 mol/L,8 h,160℃,the bamboo fiber yield was 46%,so the reaction conditions with the largest bamboo fiber yield in sodium hydroxide were selected as the optimized process.Bamboo charcoal fibers(CF)were obtained by carbonizing the bamboo fibers prepared under the optimized conditions,and then the carbon fibers were surface-modified by PDA,and nano-Fe3O4 and nano-TiO2 were supported by hydrothermal method,and bamboo charcoal with magnetic recyclability and excellent cycle performance was successfully prepared.Fiber-based photo-Fenton catalyst,and its degradation effect on methylene blue solution(MB)is still excellent after calcination in air atmosphere.Then,the factor levels were determined by single factor experiments,and the preparation process of the two catalysts was optimized by response surface methodology.(2)According to the response surface optimization results,the concentration of dopamine was 1.7 mg/mL,the mass of ferric chloride was 1.20 g,the mass of P25 nano-titania was 0.2 g,and the liquid-solid ratio was 170 mL/g as the catalysts for the preparation of TiO2/Fe3O4/PDA/CF photo-Fenton catalysts.optimal process parameters.Similarly,the dopamine concentration of 1.7 mg/mL,the mass of ferric chloride 1.25 g,the mass of P25 nano-titania 0.24 g,and the liquid-solid ratio of 165 mL/g were taken as the optimal process parameters for preparing the photo-Fenton catalyst after calcination in air atmosphere.The two photo-Fenton catalysts prepared under the optimized process parameters were both easy to separate under the action of an external magnetic field(magnet).The magnetic responsiveness and cyclability of the two catalysts remained stable after ten cycles,and the degradation rate of MB remained above 95%.SEM results showed that the photo-Fenton catalyst was fibrous before and after calcination,and its diameter was about 2-3μm.The results of Mapping analysis showed that there were five elements,which proved that PDA was successfully modified and nanoparticles were successfully loaded.XRD and XPS results showed that the catalyst contained two components,which further confirmed the successful loading of nano-Fe3O4 and nano-TiO2 particles,and the elements detected by XPS were consistent with the results of Mapping analysis.VSM results show that the photo-Fenton catalyst has paramagnetism,indicating good magnetic response performance.Pore size analysis showed that all the photo-Fenton catalysts were macroporous materials,and the number of macropores increased after calcination,and the pore size became larger.(3)The degradation kinetics of MB under different reaction systems were investigated.The results showed that MB could be slowly degraded under light and H2O2 alone,and the degradation capacity of MB was improved by adding TiO2/Fe3O4/PDA/CF catalyst under the two conditions alone.The single TiO2/Fe3O4/PDA/CF catalyst has a certain adsorption effect on MB.The degradation rate of MB for TiO2/Fe3O4/CF catalyst without PDA modification,Fe3O4/PDA/CF catalyst without TiO2 and TiO2/PDA/CF catalyst without Fe3O4 was much lower than that for TiO2/Fe3O4/PDA/CF catalyst The kinetic model was constructed and the results showed that the TiO2/Fe3O4/PDA/CF photo-Fenton catalyst had the highest reaction efficiency under the photo-Fenton system,and the TiO2/Fe3O4/PDA/CF catalyst was added under the condition of no light for single Fenton catalysis.The reaction efficiency is the lowest Finally,the main reaction group and light source in the photo-Fenton catalytic system were studied.The results confirmed that the hydroxyl radical was the main degradation group in the photo-Fenton catalytic degradation,and had the most excellent photo-Fenton catalysis under sunlight performance.(4)In order to apply the prepared catalyst in the process flow of sewage treatment plant,a photo-Fenton catalytic degradation tank was designed for application research.First,through the calculation of fluid mechanics,the photo-Fenton catalytic degradation cell was designed with a length of 12 m and a width of 2 m,with a baffle plate in the middle,a xenon lamp source at the top,an electromagnet at the bottom as a catalyst recovery device,and catalyst and H2O2 input ports on both sides.In the sewage treatment unit,the photo-Fenton catalytic degradation tank is set up after the grille and before the lifting pump room.Then,dye wastewater was selected as the target degradation product,and the effects of different catalyst dosages and different H2O2 dosages on the degradation of wastewater by photo-Fenton catalysts in practical applications were investigated.The results showed that the wastewater hydrolysis rate increased first and then decreased with the increase of catalyst input and H2O2 consumption.The degradation rate of the photo-Fenton catalyst to wastewater is much lower than that of the MB solution before,and the photo-Fenton catalyst after calcination has a slightly higher degradation rate than the photo-Fenton catalyst before calcination. |
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