Study On Marine Bacterial Inactivation By In-situ H₂O₂ Photoproduction Over AgQDs Loading Oxides Photocatalysts

Ballast water is vital for stabilizing the balance of linear ocean transportation vehicles throughout the invagitation process,but its presence unavoidably causes additional undersirable issues.It is important to conserve the diversity of ocean marine species and environmental protection in the ballast water treatment process in a rational way.Photocatalytic treatment of ballast water and H₂O₂synthesis has been widely explored and implemented to overcome the problem of massive energy consumption and very damaging constants in traditional approaches.In this thesis,we focused on the inactivation of marine microorganisms and the in-situ synthesis of H₂O₂in natural seawater using AgQDs loading oxide semiconductors,and we discussed the photocatalytic mechanisms in depth.Firstly,we investigated the marine bacterial inactivation and the in-situ H₂O₂production of AgQDs/Zn O via solvothermal method.The results demonstrated that AgQDs with a size of4.1 nm had a great sterilizing rate,with the 200AgQDs/Zn O having the best inactivation of marine microorganisms.HR-TEM,UV-Vis,EIS,TPR,and Mott-Schottky et al demonstrated that the valance band of Zn O positively shifts,which is beneficial for the synthesis of H₂O₂via the 2e^-oxygen reduction reaction,and decomposition further into active oxygen species·OH for the inactivation of marine microorganisms efficiently.Furthermore,selectively producing H₂O₂by the size effect of AgQDs dominate the catalytic performance rather than charge separation efficiency in this system.Secondly,we prefer to investigate different oxides supporters includes WO₃,Ce O₂,Bi₂O₃,V₂O₅,Mo O₃,Sn O₂,and Ti O₂loaded by AgQDs for the production comparison of H₂O₂in seawater.The result reveal that Bi₂O₃had a substantial capacity of the H₂O₂production that reached 24.39μM at the same loading of AgQDs,and also proved the universal laws that oxides loaded with AgQDs could generate H₂O₂in natural seawater.Above all,based on previous comparison investigations,Bi₂O₃loaded with 7%AgQDs performed the highest ability of inactivation for marine microorganisms and synthesis of H₂O₂,with inactivation efficiency rate and production yield almost reaching 87.6%and 35.62μM,respectively.Meanwhile,the effect of AgQDs content on structural and catalytic performance has been investigated,the results show that the valance band of Bi₂O₃positively shifts after the introduction of AgQDs,and that more hot electrons were excited by the photoillumination of AgQDs,converting molecular oxygen into H₂O₂and decomposing into the essential catalytic species·OH to inactivate marine bacteria in seawater.AgQDs acted as an oxygen adsorption core,charges separation core and photocatalytic activation core.This work offers some experimental value for photocatalytic H₂O₂production and optimal methods for ballast water treatment.