| Graphite phase carbon nitride（g-C3N4）as a semiconductor material has been widely concerned in photocatalytic water treatment.However,the photocatalytic activity of bulk gC3N4 under visible light still needs to be improved due to its narrow wavelength range of light absorption,small specific surface area,and high recombination rate of photocarriers.Therefore,in this paper,two different modification methods were used to improve the photocatalytic degradation of Rhodamine B（Rh.B）and photocatalytic sterilization of g-C3N4 in water treatment field.At the same time,the composite fiber membrane material of photocatalyst was prepared by electrostatic spinning technology.And a supported flat-plate photocatalytic reactor was designed using photocatalyst film and computational fluid dynamics（CFD）simulation was carried out to optimize the location and the amount of photocatalyst film to make it more suitable for industrial wastewater treatment.Research contents include:（1）Using sodium phosphate as phosphorus source,a series of phosphorus-doped carbon nitride（CN-Px）materials were prepared by hydrothermal method and thermal polymerization.The addition of phosphorus changes the morphology of the original g-C3N4,increases the specific surface area of g-C3N4,and broadens the light absorption wavelength range of the original photocatalyst.The addition of phosphorus widens the range of light absorption wavelength and adjusts the electronic structure,surface defects,and active sites of the photocatalyst to optimize the photocatalytic performance.It can be confirmed that doping engineering can improve the separation of photogenerated electrons（e-）and holes（h+）,and accelerate the separation and transfer capacity of photogenerated carriers from the photoluminescence and electrochemical impedance tests.The experimental results show that the photocatalytic degradation and bactericidal performance of CN-P6 are better than the original graphite phase carbon nitride.CN-P6 could degrade 99.43%Rh.B within 50 min and sterilize 99.95%Acinetobacter baumannii 28 within 120 min.CN-P6 can be used as a candidate material for photocatalytic water treatment due to its simple synthesis and good photocatalytic effect.（2）P-g-C3N4/BiOBr S-Scheme photocatalysts were prepared by using P-g-C3N4 as substrate and BiOBr nanoflowers were loaded onto its surface.After doping with phosphorus,the specific surface area of graphite phase carbon nitride is increased,and the reaction sites combining with BiOBr are increased.At the same time,the band gap is adjusted to improve the separation and transfer rate of electrons on P-g-C3N4/BiOBr surface.P-g-C3N4/BiOBr heterojunction photocatalyst has strong visible light absorption ability,can kill 99.9999%of Acinetobacter baumannii 28（AB 28）,99.98%of Staphylococcus aureus,and degrade 99.83%of Rh.B.The synergistic effect of phosphorus doping and BiOBr heterojunction on visible light utilization and photocarrier separation may be the main reason for the remarkable enhancement of photocatalytic performance.By testing and evaluating the performance of Pg-C3N4/BiOBr,the main active particles of photocatalytic sterilization and degradation were identified.Based on the structure analysis,photoelectric properties,and photocatalytic process,the possible mechanism of S-scheme heterojunction photocatalyst was proposed.It is this Sscheme heterojunction that can maintain both the excellent reducing ability of P-g-C3N4 and the excellent oxidizing ability of BiOBr.The e-with strong reducing ability accumulated in the conduction band（CB）of P-g-C3N4 can react with O2 to generate superoxide free radicals（·O2-）,and the h+ with strong oxidizing ability accumulated in the valence band（VB）of BiOBr can react with H2O to generate hydroxyl radicals（·OH）.The combined action of h+,·O2and ·OH finally improves the bactericidal efficiency.This strategy can be extended to many heterojunction photocatalysts with excellent solar energy conversion performance.（3）The combination of photocatalyst and polyacrylonitrile fiber was realized by electrostatic spinning technology.The photocatalytic performance of the photocatalyst composite fiber was measured under simulated sunlight.The photocatalyst composite fiber could kill 99.63%AB 28 and degrade 81.24%Rh.B.The composite nanofiber membrane reduces the consumption of catalyst powder in use and is convenient for recycling.The soft flat film is ideal for use as part of a photocatalytic reactor and can be easily pasted onto the reactor surface.Membrane loaded plate type photocatalytic reactor was designed,and the corresponding CFD simulation was conducted.The distribution of the catalyst was optimized according to the simulated data to make it more suitable for the industrial wastewater treatment. |
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