Fabrication Of Photocatalytic Microchannel Reactor And Degradation Of Organic Wastewater

In the field of photocatalytic degradation of organic wastewater,conventional photocatalytic reactors suffer from low incident light efficiency,low photocatalyst recovery and mass transfer limitations.Hence,in this thesis,a high flow rate photocatalytic microchannel reactor was designed by combining the green and sustainable utilization of photocatalysis technology and the microchannel reactor technology with high mass transfer rate.The monolithic photocatalyst was prepared using porous sponge as the carrier,and the successful preparation of the catalyst was demonstrated by SEM,TEM and XRD characterization.The photocatalytic activity evaluation experiments were conducted with methylene blue（MB）as a model pollutant to investigate the mechanism of photocatalytic degradation process.The main research is as follows:（1）Ag/AgCl photocatalysts were grown in situ on a polydopamine-modified melamine sponge backbone using a simple impregnation method.The prepared monolithic photocatalyst was assembled into a microchamber between two quartz glasses to construct a monolithic photocatalytic microchannel reactor.This monolithic microreactor can shorten the diffusion distance of pollutant molecules to the active center and perturb the liquid flow,thus significantly enhancing the mass transfer performance of this monolithic microreactor.The results of photocatalytic evaluation experiments showed that the microreactor had good adsorption and photocatalytic performance and was able to completely degrade MB within 10 min.The microreactor was able to treat organic wastewater up to 250 L/h·m²（40 m L/min）,which is 6 times higher than the microfluidic photoreactor（about 40 L/h·m²）.The cycling experiments showed that the microreactor has good stability and the photodegradation efficiency can still reach more than 90%after five cycles of experiments.In addition,a simple in situ chemical recovery method was demonstrated to extend the lifetime of MS/PDA/Ag/AgCl photocatalyst use.（2）To solve the problems of poor adsorption ability and low efficiency of photogenerated electron-hole separation and transfer of Ag/AgCl-based photocatalysts.Ti O₂/ZIF-8/AgCl/Ag composite photocatalysts were synthesized on a polydopamine-modified melamine sponge backbone by hydrothermal and photoreduction methods.Ag/AgCl can facilitate the transfer of photogenerated carriers with the assistance of ZIF-8,which enables it to maintain stability.In addition,the composite structure of Ti O₂/ZIF-8/AgCl/Ag can modulate the charge transfer mode and the compounding ability of photogenerated electrons and holes is reduced,which improves the efficiency of photocatalytic removal of pollutants.The prepared monolithic photocatalysts were assembled into the continuous channels of the microreactor to construct a monolithic photocatalytic microchannel reactor with better wastewater treatment capacity.The photocatalytic activity evaluation experiments showed that the microreactor had good adsorption and photocatalytic performance and was able to completely degrade MB within 8 min.Organic wastewater treatment capacity can reach 312.5 L/h·m²（45 m L/min）at high flow rates.The k value of this microreactor was 9.97×10^-1 min^-1,while that of the intermittent experiment was1.13×10^-1 min^-1,and the photocatalytic rate was improved by about 10 times.