Study On Preparation Of Bismuth Vanadate-based Photocatalyst And Their Application In Photodegradation Of Trace Pollutant

Recently, more and more attentions have been paid on resistance bacteria andenvironmental ecosystems problem of trace antibiotic. It is difficult to dispose the antibioticwastewater with the traditional biological or chemical treatment, which is characterized ashigh concentration, dark color, great toxicity and biorecalcitrant. Photocatalytic oxidation hasreceived much attention as one of the most promosing technologies because it exhibits manycompelling advantages such as superior redox capabilities, chemical stability, mild reactionconditions and no secondary pollution. Currently, to find visible-light-driven photocatalystswith high activity is of utmost importance for application of photocatalytic oxidation. As anovel visible-light-driven photocatalyst, BiVO4has been extensively studied for thedegradation of organic contaminants and water splitting. Unfortunately, the high rate ofrecombination of photogenerated electron/hole pairs and a low quantum yield limit theapplication for environment remediation.The main work of this paper is focused on the modification of BiVO4, via nano-design,combination with reduce graphene oxide, forming semiconductor composites, depositingnobel metal. The samples were characterized by X-ray diffraction (XRD), scanning electronmicroscopy (SEM), transmission electron microscope (TEM), X-ray photoelectricspectroscopy(XPS) and ultraviolet and visible diffuse reflectance spectra (UV–Vis DRS). Thephotocatalytic activity of the synthesized products was evaluated by degradation ofciprofloxacin (CIP) under a xenon lamp irradiation(cut off λ≤420nm light through an opticalfilter). There are mainly four parts in this paper:(1) A highly effective visible-light-driven octahedral monoclinic BiVO4nanocrystalphotocatalyst was successfully synthesized by a facile microwave-assisted method in thepresence of sodium dodecyl benzene sulfonate (SDBS). Result shows that reaction time andSDBS play key roles in the formation of octahedral nanocrystals. The octahedral BiVO4nanocrystals possess high CIP degradation ratio (79%) under visible-light irradiation in60min. The activity enhancement of octahedral BiVO4nanocrystals can be ascribed to the fastseparation of charge-carriers caused by the smaller size and unique morphology.(2) we have successfully synthesized the RGO-BiVO4composite photocatalysts via avery facile microwave-assisted in-situ growth method. The reduction of GO into grapheneduring the microwave heating process is sufficiently proved by XRD patterns, Raman spectras and the XPS spectrum. The as-produced RGO-BiVO4composite photocatalysts showtremendous enhancements on the CIP photocatalytic degradation ratio under visible-lightirradiation in60min. The2wt%RGO-BiVO4sample exhibits the highest CIP degradationratio (68.2%). The enhancement of photocatalytic activity of RGO-BiVO4compositephotocatalysts is due to the effective separation of photo-induce electron-hole pairs by RGO.(3) The BiVO4-Bi2WO6nano-heterojunction photocatalysts were synthesized by a facilesonochemical method with microwave-assisted synthesized BiVO4nanoparticles andhydrothermally synthesized Bi2WO6nanosheets as starting materials. The results showed thatthe BiVO4nanoparticles scattered on the Bi2WO6sheets by the dispersion role of ultrasonicirradiation indicating the heterojunction structure formed. Compared with the single-phaseBiVO4and Bi2WO6counterparts, BiVO4-Bi2WO6nano-heterojunction photocatalysts showenhanced photocatalytic degradation activities in visible-light-driven CIP degradation.Particularly, when R(Bi2WO6/BiVO4)=10wt%, the products exhibit the highest CIPdegradation ratio in60min of77%under visible-light illumination. The tentative mechanismof the interface charge transfer (IFCT) effect in the BiVO4-Bi2WO6heterojunction structure isalso discussed by using the band position calculation.(4) A series of novel Pt/BiVO4photocatalyst was synthetized by microwave method andphotoreduction deposition process. The results suggested that Pt0was formed on the surfacedof BiVO4. Compared with the single-phase BiVO4, Pt/BiVO4photocatalysts showed enhancedphotocatalytic degradation activities in visible-light-driven CIP degradation. Particularly,when Rw(Pt/BiVO4)=2%, the products exhibited the highest CIP degradation ratio in60minof87.5%under visible-light. The enhanced photocatalytic activity should mainly beattributable to the presence of Pt nanoparticles, which suppressed the recombination ofphotogenerated electrons and holes and promoted the efficiency of electron-hole separation.