| In recent years,antibiotic pollutants represented by tetracycline have been fre-quently detected in water,posing a great threat to the ecological environment and human health.Photocatalytic oxidation technology based on semiconductor materials has significant advantages over traditional water treatment processes in removing such organic pollutants.However,single-phase photocatalysts have weak visible light absorption ability,low photon yield and low efficiency of photogenerated elec-tron-hole pair separation,which seriously restricts its photocatalytic activity in prac-tical applications.Therefore,in this study,a series of composite photocatalysts were constructed based on graphite carbon nitride?g-C3N4?,bismuth-based semiconductor materials and Metal-organic framework?MOFs?materials.Meanwhile,the physico-chemical structure,optical absorption,photoelectrochemical properties and photo-catalytic activity of as-prepared photocatalysts were systematically analyzed by vari-ous characterization methods.Based on the above contents,the main works of this paper are as follows.In order to promote the effective separation and transmission of photo-generated carriers of single-phase g-C3N4 while retaining its strong redox ability of electrons and holes,a series of BiOCOOH/g-C3N4 composites with three-dimensional flower structure were firstly prepared by thermal polymerization and hydrothermal method.Subsequently,these catalysts were characterized and optimized.The results indicated the obtained BiOCOOH/g-C3N4 sample exhibited the best photoelectrochemical per-formance and photocatalytic activity when the molar ratio of Bi?NO3?3·5H2O to g-C3N4 was 1:1.After irradiation by 35 W Xenon light for 120 minutes,the photo-catalytic removal rate of amino black 10B by BiOCOOH/g-C3N4 composite was89.16%.On this basis,the?-Bi2O3/g-C3N4 composite catalyst was synthesized by one-step calcination optimized BiOCOOOH/g-C3N4 under air atmosphere.The ob-tained?-Bi2O3/g-C3N4 composite photocatalyst had the best light intensity for amino black 10B when calcination temperature was 400?,and its degradation process fit-ted well with the pseudo-first-order kinetics formula according to the Lang-muir-Hinshelwood?L-H?model.After 120 min irradiation,the photodegration effi-ciency of?-Bi2O3/g-C3N4 was 97.09%.The results of structural and photoelectro-chemical characterization showed that the prepared photocatalyst had higher photo-current density?1.0?A/cm2?,lower charge transfer resistance and higher carrier con-centration.In addition,·O2?was proved to be the main active species for photocata-lytic degradation of amino black 10B over?-Bi2O3/g-C3N4 composite catalyst.In order to further improve the specific surface area,visible light absorption ca-pacity and carrier separation and transport efficiency of the composite,MIL-53?Fe?and MIL-100?Fe?were prepared by solvothermal method and oxidizing racal-promoted facile synthesis method,respectively.Whereafter,dual Z-scheme MIL-53?Fe?/?-Bi2O3/g-C3N4ternarycompositesanddualZ-scheme MIL-100?Fe?/?-Bi2O3/g-C3N4 ternary composites were obtained by a simple precipi-tation method.The results showed that the load of MIL-53?Fe?and MIL-100?Fe?sig-nificantly broadens the light absorption range of the composite catalyst,and the ter-nary composites could achieve the best photocatalytic efficiency when the MIL-53?Fe?andMIL-100?Fe?loadingswere32%and15%,respectively.MIL-53?Fe?/?-Bi2O3/g-C3N4 could completely remove amino black 10B within 45minutes and the kinetic constant was k=0.08434 min-1.Besides,the removal rate of amino black 10B and Lomefloxacin over MIL-100?Fe?/?-Bi2O3/g-C3N4 was 98.47%and 77.19%,respectively after 120 min of irradiation.Finally,tetracycline in aquatic environment was selected and served as the target contaminat to evaluate the photocatalytic properties of the as-fabricated catalysts un-derthesamereactionconditions.Theresultsrevealedthat MIL-53?Fe?/?-Bi2O3/g-C3N4 ternary composites exhibited the highest photocatalytic efficiency,in which 94.57%tetracycline could be eliminated within 120 min under 35W Xenon light irradiation.Moreover,the photocatalytic degradation of tetracycline accorded with L-H kinetic model,and the corresponding reaction rate constant was0.01905 min-1.In addition,the photocatalytic removal efficiency of tetracycline by MIL-53?Fe?/?-Bi2O3/g-C3N4 composite catalyst was confirmed affected many factors,such as the amount of photocatalyst,initial pH value,coexisting ions and humus in solution.Notably,·O2?,h+,H2O2 and·OH could all participated in the photocatalytic reaction,and tetracycline would undergo a series of hydroxylation,dealkylation,ring opening as well as other redox reactions under the action of these active species and eventually be completely mineralized into CO2 and H2O. |
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