Research On Preparation And Application Of The Novel Bismuth Tungstate Heterojunction Composites

Bi2WO6has attracted extensive attentions owing to the highest photocatalyticactivity among the above Bi3+-based oxides under visible light irradiation. However,its highly efficiency of electron-holes recombination prohibits the desirable catalyticactivity under visible light irradiation. Therefore, it is essential to improve the chargeseparation efficiency of Bi2WO6and extend the spectral responsive range. But so far,most of the modified research for Bi2WO6is still stayed in the lab preparation. Still,the photocatalytic environmental purification was not realized. In this paper, it wasattempted to modify and load Bi2WO6to synthesize the novel heterojunctions withenhanced visible-light photocatalytic activity, which was applied to practicalapplication.Bi2WO6/Bi2O3heterojunction was synthesized to modify Bi2WO6. And then,Bi2WO6/Bi2O3was laoded on the scoria and applied to the self-designed continuoustype photocatalytic reactor. What is more, Bi2WO6/Bi2O3was further corrected andmodified. The novel multicomponent heterojunctions with enhanced visible-lightresponses and high photogenerated electron-holes separation were synthesized bysulfur doped and carbon loaded. The mechanisms of the forming and the enhancedphotocatalytic activities for the the novel multicomponent heterojunctions wereexplored by a series of characterization. The best multiple heterogeneous wasdetermined by the comparison of photocatalytic activity, which was applied to themultiple sections continuous photocatalytic reactor. From the above, the main worksand the relevant results are as follows:First, Bi2WO6/Bi2O3heterojunction constructed: Bi2WO6/Bi2O3heterojunction(BWO) was synthesized via a facile one-step hydrothermal route. The experimentalresults showed that the best molar ratio of sodium oleate and bismuth nitrate (SO:Bi) to synthesize Bi2WO6/Bi2O3was1.25:1for synthesis BWO4. Under visible-lightirradiation, the photodegradation rate of RhB (10-2g/L)was99.50%with BWO4(1.00g/L) in90min. It suggested that Bi2O3was synthesized due to the addition ofsodium oleate. The typical p-n heterojunction was constructed in Bi2WO6/Bi2O3,which enhanced visible-light photocatalytic activity of the photocatalyst.Second, the immobilization of Bi2WO6/Bi2O3and the application of thecontinuous type photocatalytic reactor: Bi2WO6/Bi2O3laoded scoria (BWO@S) wassynthesized via a facile one-step hydrothermal route. The experimental results showedthat Bi2WO6/Bi2O3was laoded evenly on the surface of the scoria. BWO@S exhibitedgreat photocatalytic activity for degradation of RhB. Under visiable-light irradiation,the photodegradation rate of RhB (10-2g/L) with BWO@S (30.00g/L) was98.91%in90min. Moreover, the continuous type photocatalytic reactor was applied withBWO@S. The results of the degradation of RhB (2×10-3g/L) showed that thephotodegradation rate was98.91%under the best hydraulic retention time7.46h.Hence, it determined that the photocatalytic reactor showed great photodegradationfor organic pollutants.Third, the doping S modified Bi2WO6/Bi2O3: S doped Bi2WO6/Bi2O3multicomponent heterojunction (S-BWO) was successfully synthesized via a one-stephydrothermal route. The experimental results showed that the best molar ratio ofthiourea and sodium oleate (S:SO) to synthesis S-BWO was1:4for synthesisS-BWO3. Under visible-light irradiation, the photodegradation rate of RhB (10-2g/L)was98.11%with S-BWO3(1.00g/L) in20min. It has indicated that doping S2-canenter into the crystal lattice of Bi2O3via replacing oxygen atom of the Bi–O to formthe Bi–S, which form the lattice defects. The lattice defects enhanced thephotocatalytic activity of S-BWO.Fourth, carbon loaded modified Bi2WO6/Bi2O3: Bi2WO6/Bi2O3loaded reducedgraphene oxide multicomponent heterojunction (BWO@R) was successfullysynthesized via a one-step hydrothermal route. In the synthesis process, graphene oxide was reduced into graphene, which simplified the preparation process withoutthe secondary reduction. The experimental results showed that the best additionpercent of graphene oxide (GO%) to synthesis BWO@R was2%for synthesisBWO@R2. Under visible-light irradiation, the photodegradation rate of RhB (10-2g/L)was99.60%with BWO@R2(1.00g/L) in20min. Meanwhile, BWO@R2ownedgreat adsorption, the adsorption rate reached88.2%. It was suggested by thecharacterizations that the crystal structures were not changed by RGO. Grapheneowns two dimensional structure, high conductivity and electron mobility. Hence,loaded RGO greatly enhance the photocatalytic activity of BWO@R. Moreover, theself-designed multiple sections continuous photocatalytic reactor was applied withBWO@R2. The results of the degradation of RhB (5×10-3g/L) showed that thephotodegradation rate was98.91%under the condition of the optimal hydraulicretention time was100s. Hence, it determined that the photocatalytic reactor showedgreat photodegradation for organic pollutants.