Study On Visible-light Photocatalyst Based On Polyacrylonitrile

The polyacrylonitrile was prepared by aqueous deposition polymerization.The viscosity average molecular weights of polyacrylonitriles were determined using the ubbelohde viscosity meter.The effects of different temperature and time on structure and property of PAN were investigated during teat-treatment process.CPAN polymers were characterized by Fourier transform infrared spectra(FT-IR),UV-Visible diffuse reflectance spectroscopy(DRS),Photoluminescence emission(PL),X-ray photoelectron spectroscopy(XPS),and thermogravimetry-differential thermal analysis(TG-DSC).Results show that the nitrile(C=N)groups of PAN were translated to-C=N groups during heat-treatment process,forming-C=N-C=N-conjugated structure.With the improvement of heat treatment time and temperature,relative cyclization rate of CPAN increased.The formation of-C=N-C=N-conjugated structure promoted the absorption of visible light of CPAN granules.With the improvement of heat treatment time and heat treatment temperature,the visible light absorptive ability of CPAN enhanced.The binding energies of Cls and Nls of CPAN indicate the conjugated structure formation.The visible light photocatalytic activity and stability of CPAN particles were evaluated by the degradation of rhodamine B in an aqueous solution under visible light.The effects of different teat-treatment temperature and time on visible light photocatalytic activity of CPAN were investigated.Results reveal that the visible light photocatalytic activity of CPAN particles was best when the viscosity average molecular weights of CPAN was 1.2x 105,heat treatment temperature was 220 ?,heat treatment time was 2.0h.The mechanism of the rhodamine B degradation was also discussed.The degradation process of rhodamine B was measured by UV-vis absorption spectroscopy and high pressure liquid chromatograph.The results show that the degradation process of rhodamine B includes N-deethylation step by step and further degradation.The redox curve of CPAN was measured using cyclic voltammetry,and the potential energy of the conduction band and valence band were also calculated.Benzoquinone(BQ)was used as an effective quencher of ·O2-.Obviously,the addition of benzoquinone most acutely depressed the degradation of RhB.It indicates that thee-is the mainly active species.Photogenerated electron can react with oxygen molecules adsorbed on the surface of CPAN particles to product ·O2-radicals,and it can degrade RhB molecular directly.In addition,the cyclic experiments show that the photocatalytic activity of the CPAN enhanced obviously with the increase of cycles,therefore,CPAN as visible light catalyst has good application prospect.