Visible Light Photocatalytic Activity Of Vitamin B₁₂-based Composite In The Presence Of RhB For DDT Dehalogenation

Vitamin B₁₂ and its derivatives have attracted the wide attention of researchers due to their excellent catalytic.In recent years,some researchers have immobilized vitamin B₁₂ and its derivatives on carriers with excellent properties to prepare composite catalysts and used in a series of important reactions.In this paper,Vitamin B₁₂ derivative[（CN）（H₂O）Cob（III）7COOH]Cl was immobilized on the surface of reduced graphene oxide（PIL/rGO）and P25 TiO₂ respectively and the photocatalytic activities of the obtained composites for 1,1-Bis（4-chlorophenyl）2,2,2-trichloroethane（DDT）dechlorination reaction were investigated under visible-light irradiation.The main contents are as follows:1.The photocatalytic activity for DDT dechlaorination of the nanocomposite B₁₂-PIL/rGO in the presence of the photosensitizer RhB was studied visible-light irradiation.The results proved that rGO acted not only as support but also as electron mediator between the B₁₂ catalyst and the photosensitizer RhB.In addition,rGO showed a certain catalytic activity for DDT dechlorination.In this photocatalytic system,DDT was converted completely after 60 min visible-light irridation,.The yields of the monodechlorination product DDD and the didechlorination products were 34%and 62%respectively.When the irradiation time increased to 3 h,DDD was also completely converted to didechlorinated and tridechlorinated products.The composite catalyst B₁₂-PIL/rGO can be separated by simple centrifugation and recycled for use with only a slight decrease of catalytic activity due to the loss of catalysts during the recyling.2.The novel composite RhB-TiO₂-B₁₂ was prepared successfully through immobilizing B₁₂ derivative[（CN）（H₂O）Cob（III）7COOH]Cl and RhB on the surface of commercial P25 TiO₂ nanospheres with a simple one-step reaction.Its structure and morphology were characterized by X-ray powder diffraction（XRD）,scanning electron microscopy（SEM）,diffuse reflectance UV-visible spectroscopy,Zeta potential measurement.The contents of B₁₂ derivative and RhB in the composite RhB-TiO₂-B₁₂ was 9.2×10^-5 mol·g^-1 and 9.0×10^-5 mol·g^-1,which was determined by UV-vis absorption spectra.The photocatalytic performance of the composite RhB-TiO₂-B₁₂ was investigated in the presence of TEOA as electron donor under visible light.The experimental results showed that the conversion rate of DDT can reach 100%after 60 min irradiation.The yields of the monodechlorinated product and the didechlorinated products were 70%and 14%respectively.Compared with the simple mixture catalytic system of B₁₂ derivertive and RhB,the photocatalytic activity enhanced obviously,which indicated that the introduction of semiconductor TiO₂ as support accelerated the electron transfer rate from the photosensitzer to the B₁₂ catalyst and inhibited the recombination of electrons.In this catalytic system,the B₁₂ catalyst and the photosensitizer can be separated together with the support TiO₂by simple centrifugation and reused without significant loss of catalytic activity.In general,two novel hybrid photocatalytic systems with B₁₂2 derivative as catalyst and RhB as photosensitizer for dehalogenation have been developed successfully.They all exhibited excellent photocatalytic activities for DDT dechlorination.In this work,a new research idea and method for constructing high efficient,energy-saving and environmentally friendly photocatalytic system was provided.