Preparation, Characterization And Photocatalytic Activity Investigation Of Visible Light-responsive Temperature Controlled Photocatalyst

Recently, environmental purification using TiO2 as a photocatalyst under solar irradiation has attracted a great deal of attention due to its non-toxic, inexpensive and highly reactive nature. Among them, with a visible light response, multi-walled carbon nanotubes(MWCNTs) /TiO2 composite photocatalyst can make photoinduced electrons(e-)-hole(h+) of wide band-gap TiO2 photocatalytic materials effective separation, effectively inhibiting the recombination of photo-generated electron-hole and making their responsive spectrum expand to the visible light, greatly enhancing the TiO2 photocatalytic reaction efficiency. However, in practical applications, ultra-fine MWCNTs/TiO2 powder can be aggregated easily in solution, but hardly separated and recovered. In addition, because of the polar surface of the TiO2, its interface compatibility with organic phase is poor, the application of MWCNTs/TiO2 is limited to a large extent in degradation of organic pollutants.Poly(NIPAM-co-MAH-β-CD) hydrogel consists of N-isopropyl acrylamide(NIPAM) unit with temperature sensitive "on-off" property and P-cyclodextrin derivatives of maleic anhydride(MAH-β-CD) unit with molecular identification ability, and in water it has good swelling, thermo-sensitive and transparent features. Besides, the polymer contains hydroxyl functional groups which can react with TiO2 to form coordination bond. This subject prepared a new type photocatalyst material of poly(NIPAM-co-MAH-β-CD) load-oriented MWCNTs/TiO2 with temperature-sensition, molecular identification, stability, uniformity properties and functions.In this paper, based on the reported literatures, NIPAM, MAH-β-CD, MWCNTs/TiO2 composite material unites first were prepared, and then, temperature responsive microspherical gels of NIPAM and P-cyclodextrin carrying vinyl carboxylic acid functional groups were synthesized by a surfactant-free emulsion polymerization method with N, N'-methylene bisacrylamide(BIS) as crosslinker, potassium peroxydisulfate(KPS) as initiator. The hydrogel's composition was determined by element analysis. Equilibrium swelling ratio(ESR) of hydrogels were tested under different temperature in water, and the effects of ratios of reactants, the amount of cross linker, the amount of initiator and reaction temperature on thermosensitivity of hydrogels were investigated thoroughly.Then, organic-inorganic composites were prepared with multi-walled carbon nanotubes (MWCNTs)/TiO2 photocatalysts embedded within colloidal particles of a cross-linked, thermally responsive poly(NIPAM-co-MAH-P-CD). The composites were characterized by X-ray diffraction(XRD), transmission electron microscope(TEM), thermo gravimetric analysis (TG) and ultraviolet-visible absorption spectra(UV-vis). Equilibrium swelling ratio(ESR) of composites were tested to show their temperature-sensitive property in water, and the effects of ratios of reactants, the amount of cross linker, the amount of MWCNTs/TiO2 on photocatalytic activity were studied. The results indicate that the prepared samples were sphericity, anatase phase with mean size of 20～25 nm, and the introduction of the hydrogels could make MWCNTs/TiO2 recovered easily, as well as inhibiting it to aggregate and lose seriously in practical process.