Photodegradation Of Organic Contaminants In Wastewater Using Ti-Bi(Ag) Metal Oxide Heterostructures

With the development of industry,a large number of organic pollutants release into the water system,which has significant impact on ecosystem and human health.Therefore,it is required to develop alternative processes to remove organic pollutants from wastewater.Photocatalysis is one of the potential technologies used for wastewater remediation due to its safe and non-toxic,mild reaction conditions and mineralization of organic pollutants.However,the key issues for photocatalysis is to develop a highly efficient and stable semiconductor photocatalytic material with high solar energy utilization and quantum yield.In this study,Ti-Bi(Ag)metal oxide heterostructures were constructed to broaden the light response and to reduce the recombination of photogenerated carriers.The photocatalytic degradation of oxides is evaluated by using dye or antibiotics as a target organic contaminant.On the basis of both photocatalysis and characteristics,the structure-activity relationship and corresponding photocatalytic enhancement mechanism are proposed.The main research findings are as follows:1.TiO2 hollow nanofibers(ELTiO2)grafted Ag/AgCl is fabricated via electrospinning-precipitation method.Compared with Ag/AgCl and Ag/AgCl-SGTiO2(sol-gel synthetized TiO2),2.89 and 1.59-fold enhanced in the photodegradation rate toward methyl orange is observed over Ag/AgCl-ELTiO2 under visible light irradiation.The enhancement of photocatalytic activity is mainly attributed to the higher content of the exposed AgCl ?111} facet,which is beneficial for the separation of photogenerated carriers and accounts for more active sites.Moreover,Ag/AgCl-ELTiO2 shows a better photostability than bare Ag/AgCl.2.Ag2O/TiO2 heterostructure has been constructed by loading corner-truncated cubic Ag2O on TiO2 hollow nanofibers via electrospinning-precipitation method.Compared to individual Ag2O and TiO2,Ag20/TiO2 heterostructure exhibits obviously enhanced photocatalytic activity for the photodegradation of methyl orange(MO)under visible light irradiation.The composite with molar ratio of Ag20Oto TiO2 at 4:10 shows the best photocatalytic activity,which MO can be degraded 93%within 6 min.The superior activity is mainly attributed to the surface plasmon resonance(SPR)effect of metallic Ag in-situ produced during the photocatalytic process,which can favor electron transfer to conduction band of TiO2,leading to the efficient separation of the photogenerated carriers,thus a superior photodegradation activity.3.Visible-light-induced BiOCl/Bi/P25 composite materials are prepared via a hydrothermal method,and evaluated by degradation of methyl orange aqueous solution.It exhibits the highest photocatalytic efficiency,which is 23.9 and 53.6 times higher than that of Bi/BiOCl and P25,respectively.The superior activity is attributed to the surface plasmon resonance(SPR)of metallic Bi,and the efficient separation of the photogenerated carriers with the aid of BiOCl/P25 heterostructure.In the photodegradation process,holes can react with Cl-ions to form Cl· radicals,which both can oxidize MO.Then,Cl· radicals reduce to Cl-again,forming a circulation and improving the photocatalytic activity.4.Bismuth titanates have fabricated via electrospinning combined with calcination at different temperatures.BiOCl/Bi2Ti2O7 nanorod heterostructures are obtained at 500?.It possesses excellent photocatalytic efficiency and stability for the degradation of tetracycline hydrochloride(TC-HCl)under simulated solar light.The excellent catalytic activity is predominantly attributed to the heterostructure between BiOCl and Bi2Ti2O7,which accelerates the separation of photogenerated carriers while narrow band gap of Bi2Ti2O7 enhances solar energy utilization.On the basis of energy band engineering,scavenger tests and LC-HRMS analysis,the possible degradation pathway of TC-HCl and photocatalytic mechanism were proposed.