Preparation Of Bi₂MoO₆ Photocatalysts Modified By Bismuth Halide Oxide And Its Degradation Of Tetracycline

Tetracycline（TC）,which is widely used in fighting infections and promoting animal growth,accumulates in the aqueous environment and poses a threat to human health and ecosystems that should not be underestimated.Therefore,it is imperative to explore efficient and environmentally friendly technologies for eliminating broad-spectrum antibiotics from the environment.Photocatalysis is gradually becoming a research focus,but the lack of efficient and recyclable visible light-driven photocatalysts limits it practical applications.To solve this problem,a catalyst of bismuth halide oxide-doped Bi₂Mo O₆was successfully prepared by a solvothermal method to achieve modification of photocatalytic materials,characterized and investigated the effects of environmental factors on TC photodegradation,and determined the cycling stability and main active substances.Finally,possible photodegradation mechanisms and degradation pathways were proposed.This provides an innovative perspective for the construction of novel photocatalysts,and also presents theoretical research basis and solution ideas for the removal of organic pollutants（antibiotics）by photocatalysis in environmental remediation.（1）The nano-flower spherical Bi OCl-BMO photocatalyst was successfully prepared with good chemical bond formation,intact surface elements,stable crystal structure and no impurities.The specific surface area(S_BET)was 47.72 m²/g and the band gap（Eg）reached 2.54 e V.In addition,the photocatalytic degradation efficiency of 0.06 Bi OCl-BMO for TC（c₀=10 mg/L）reached 97.23%after the irradiation of350 W Xe-lamp for 100 min,which improved the removal effect by 1.6 times.And the good stability after three cycles.This is because Bi OCl-BMO provides a synergistic effect for the effective charge transfer process.The surface structure enhances the collection of light,accelerates the rate of light-generated carriers,enables the effective charge transfer to be accelerated.Moreover,the heterojunction can effectively suppress the photogenerated electron-hole pair complexes,and the gradual enhancement of absorption in visible light and the increase in the range of light absorption as well.（2）The surface nanoplate clear flower spherical Bi OBr-BMO photocatalyst was successfully prepared with S_BETof 50.18 m²/g and Eg of 2.49 e V.The photodegradation of TC by 0.22 Bi OBr-BMO light for 100 min reached 97.32%,and the high photocatalytic activity was still maintained after three cycles.The main acting radicals were:·O₂^->h⁺>e^->·OH.Proper loading can promote the formation of catalyst and shorten the combination rate of photogenerated electron-hole pairs in a short period of time.Increasing the amount of catalyst will increase the absorbed photon flux and produce more active substances.The higher concentration of TC will result in insufficient reaction active sites and reaction active substances.The degradation performance of TC is the best under neutral condition.Different light sources affect the photodegradation of TC,which will be significantly higher than the case without light,so the reaction is driven by light sources.（3）The flower spherical Bi OI-BMO photocatalyst with small nanosheet stacking was successfully prepared.The surface stacking was complex and interlaced,and the pore structure was rich.The S_BETwas53.17 m²/g,and the Eg was 1.88 e V,which possessed better photoelectric performance and crystal structure.Xe-lamp irradiation was used for photodegradation study,and we found that the photocatalytic degradation of TC under irradiation for 100 min reached 97.87%.After three cycles,the structure of of0.10 Bi OI-BMO did not change.Although the photocatalytic performance of the catalyst decreased to 85%,it still maintained high performance and stability.Moreover,free radical capture experiments and ESR tests were carried out,and it was found that·O₂^-and e^-played an indispensable role in the photodegradation of TC.According to the study,the possible degradation mechanism was proposed,and the degradation intermediates were identified,and the possible degradation pathway of TC was drawn.Namely,under the driving effect of light source,the catalyst was excited to produce active substances.Under the action of heterojunction structure,h⁺and e^-will undergo rapid transfer activities,and active substances·O₂^-,·OH,h⁺and e^-will interact with each other.TC（m/z=445）undergoes carbonylation,decarboxylation,demethylation and other reactions to convert into small molecules（m/z=218）,and finally into CO₂and H₂O.This can be very good to achieve pollution-free removal of pollutants in water.