| In recent years,the global industrialization process has gradually accelerated.Consequently the environmental pollution,especially water pollution,has become increasingly prominent.Among different water treatment methods,advanced photocatalytic oxidation technology stands out with its advantages of energy-saving and cost-effectiveness.Ti O2materials become the most classic type of semiconductor photocatalysts because they are cheap,abundant,resistant to light corrosion,and also have high photocatalytic activity.However,the problems of low solar energy utilization and low quantum efficiency restrict their wide application.Therefore,exploring effective modification methods to further improve the photocatalytic activity of Ti O2 materials is one of the current research focuses.In this work,two methods have been chosen to prepare a series of Ti O2-based photocatalytic materials,including metal ion doping modification and semiconductor heterojunction construction.And we explored these Ti O2-based photocatalysts'photodegradation effect of organic pollutants under simulated sunlight.?1?Using tetrabutyl titanate as the titanium precursor,1%mole fraction of Co2+,Ni2+,Cu2+,catalysts were used for photodegradation of 10 mg/L methyl orange and 20 mg/L syringol and characterized by XRD,DRS,PL,etc.The experimental results showed that the Sn-Ti O2 had the best photocatalytic activity.The degradation efficiency of methyl orange under simulated sunlight is 2 times of pure Ti O2,and the degradation efficiency of syringol is 6.3 times of pure Ti O2.However,the photocatalytic activity of other metal-doped Ti O2 samples has not been significantly improved.The characterization results indicated that the photocatalytic activity of metal-doped Ti O2 is not only related to the band gap and light absorbance,but also affected by many factors such as grain size,specific surface area,energy band position and so on.Especially,Sn4+enters the interior of the Ti O2 lattice in the form of substitutional doping,significantly reducing the size of Ti O2 grains and particles,increasing the specific surface area,and moving the VB position down.Therefore,the photocatalytic activity of Sn-Ti O2 sample increased.?2?Using commercial 40 nm anatase Ti O2 as the titanium source and Bi?NO3?3?5H2O as the bismuth source,black[Bi6O6?OH?2]?NO3?4?2H2O/Ti O2 composite photocatalyst?denoted as B-BOHN/Ti O2?was prepared by a mild light-treatment method.Pure phase[Bi6O6?OH?2]?NO3?4?2H2O sample?denoted as BOHN?was prepared by liquid phase method.And simple mixture?denoted as BOHN/Ti O2?was prepared by grinding Ti O2 and[Bi6O6?OH?2]?NO3?4?2H2O.Four samples were characterized by XRD,DRS,PL,etc.And four samples were used for photodegradation of 10 mg/L Rhodamine B dye.The experimental results showed that the B-BOHN/Ti O2 sample had the best performance.The degradation efficiency is 6.9 times of the anatase Ti O2 and 1.9 times of the simple blending BOHN/Ti O2sample,which is because that the presence of oxygen vacancies in the B-BOHN/Ti O2 material promoted the separation of photogenerated carriers.The further application of B-BOHN/Ti O2for the photodegradation of 50 mg/L lignin solution also showed excellent photocatalytic activity.Finally the free radical quenching experiment confirmed that the superoxide radical in B-BOHN/Ti O2 material played a major role.Therefore the possible photocatalytic mechanism of B-BOHN/Ti O2was proposed. |
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