Preparation And Study On Tetracycline Wastewater Photodegradation Of ZnO Based-Hybrid Photocatalysts

Photocatalytic technology is not only a kind of advanced oxidation process which has the advantages of fully photodegrading organic molecules and easy to operate,is also a green environmental protection technique which be used for the effective degradation of organic pollutants solar energy by solar power.Among a number of catalysts,ZnO,as a kind of wide and direct band gap?3.37 e V?n-type semiconductor,has attracted much attention due to its advantages of abundant sources,low cost,good chemical stability,high thermal stability and non-toxic.However,the recombination of photogenerated charge carriers is too fast,which results in low quantum efficiencies and limits the photocatalytic potential of ZnO.In order to deal with these problems that exist in the application of ZnO photocatalyst,we have adopted a series of methods to modify and synthesize ZnO-based photocatalysts.For ZnO material defects,combining ZnO with other semiconductors having suitable band structures to occur IPET process and HNTs being used as catalyst supports,we have used a novel wet-calcination solution for the preparation o f coupled ZnO/CeO₂@HNTs composites.Taking optical advantages of CQDs and HNTs being used as catalyst supports,we have successfully synthesized CQDs/ZnO@HNTs composite photocatalyst.Using the localized surface plasmon resonance?LSPR?of Ag to achieve plasmon-induced resonant energy transfer?PIRET?and direct electron transfer?DET?for facilitating the excitation and separation of photogenerated e–/h+ pairs,we have synthesized hamburger-like Ag@ZnO/C core-shell plasmonic photocatalysts.Thermo-responsive PNIPAM grafted and supported on ZnO/C composite photocatalysts with controllable photocatalytic activity were successfully fabricated.More details is as follows:HNTs being used as catalyst supports,we have used a novel wet-calcination solution for the preparation of coupled ZnO/CeO₂@HNTs composites and the morphology,structure,electrochemical and photocatalytic properties of these samples were characterized by TEM,HRTEM,XRD,FT-IR,UV-vis DRS,XPS,and electrochemistry tests.Photocatalytic activities of the as-fabricated samples were evaluated by the degradation of TC aqueous solution under simulated solar irradiation.The results showed that the presence and movement of water not only provides the source of oxygen,but also guara ntees the formation of uniformly distributed ZnO/CeO₂ clusters and the generation of mesoporous structures.Additionally,we also found that the calcinating temperature of 500 ?,the molar ratio of ZnO to CeO₂ about 3:1 and the 1-fold dosage of HNTs may be the potential optimal values.Compared with other samples,the S3 heterojunction photocatalyst showed the highest enhancement in the photocatalytic performance.The photodegradation efficiency of the S3 under room-temperature was calculated to be 87% within 60 min irradiation.Citric acid monohydrate and ethylenediamine as carbon source,carbon quantum dots?CQDs?solutions were prepared by microwave method.We have synthesized a novel CQDs/ZnO@HNTs heterostructure composite by precipitation-hydrothermal process.The morphology,structure,electrochemical and photocatalytic properties of these samples were characterized by TEM,XRD,FT-IR,UV-vis DRS,XPS,electrochemistry tests.Photocatalytic activities of the as-fabricated samples were evaluated by the degradation of TC aqueous solution under visible light irradiation.The results showed that the CQDs have been modified on the ZnO@HNTs materials and the great improvement for the active of the prepared photocatalyst has been achieved.With glucose as the carbon source,we have used a solvothermal approach in ethylene glycol solution for the synthesis of Ag@ZnO/C core-shell plasmonic photocatalysts.The morphology,structure,electrochemical and photocatalytic properties of these samples were characterized by SEM,EDS,TEM,XRD,FT-IR,UV-vis DRS,XPS,and electrochemistry tests.Photocatalytic activities of the as-fabricated samples were evaluated by the degradation of TC aqueous solution under visible light irradiation.The results showed that the molar ratio of ZnO to Ag about 5:1 and 0.4 g of glucose may be the potential optimal values,and the corresponding photocatalyst showed the highest photocatalytic performance and its photodegradation efficiency was calculated to be 82%.Additionally,the presences of hydroxyl radicals?·O H?,superoxide radicals?·O₂–?and singlet oxygen?1O₂?in the photocatalytic reaction system of Ag@ZnO/C photocatalyst have been demonstrated by electron spin resonance?ESR?measurements.Thermosensitive polymer functionalized ZnO/C composite was prepared from N-isopropylacrylamide used as functional monomer,N,N'-methylenebis?acrylamide?used as cross-linking agent,ammonium persulfate used as initiator,and 3-?Trimethoxysilyl?propyl methacrylate used as surface modification agent.The morphology,structure,electrochemical and photocatalytic properties of these samples were characterized by SEM,EDS,XRD,FT-IR,and UV-vis DRS analysis.The temperature-response characteristics of as-prepared samples were evaluated by the photodegradation behavior of TC catalyzed by as-prepared samples under different temperatures.The results showed that the synthesized composite photocatalysts possess the excellent and switchable photocatalytic activity.The degradation activity of PNIPAM@ZnO/C was suppressed as temperature was above the LCST,and returned to normal again as temperature was below the LCST.