Studies Of Synthesis, Application Of Coated Nano-TiO₂ Composite Photocatalysts

Semiconductor photocatalysis has become increasingly promising technology in the wastewater treatment because it is low-cost and completes the hazardous organic compound mineralization. The conflict between immobilization and photoactivity of photocatalyst is one of the main problems restraining the practical application of photocatalytic technology. In this paper, the immobilization methods, the interaction of supports and photocatalyst, photocatalytic degradation property of composite catalysts have been investigated using the novel, large surface area material of different properties as supports in order to make new progresses on the effect of supports and photocatalyst, the practical applications of photocatalytic technology . Some new results have been made.Natural montorillonite and organic montorillonite supports:Using the natural montorillonite and organic montorillonite which has a strong adsorption property as supports, certain amount of titanium dioxide is immobilized onto supports with melting/calcining and TiCl₄ acid sol method under strong acidity. The composite material is characterized by X-ray diffraction (XRD) and Transmission electron microscopy (TEM). It is found that the single TiO₂ diffraction peak did not appear in the composite material. The basal spacing of (001) has been increased from 15.5 A to 29.4 A in the nature montorillonite support and the basal spacing of (001) of organic montorillonite has not changed. This result demonstrated that the insertion of species titanium hydration cation with positive charges exchange reaction occurred in the galleries of nature bentonite but organic bentonite did not. It is proved by TEM that the TiO₂ particles are well-dispersed on the surface and pass into the lattice layer of bentonite. These results indicate that the strong interaction of TiO₂ and bentonite surface restrains the TiO₂ crystal growing.The result of photo-catalytic degradation of active brilliant red (X-3B) shows that the decoloring ratio is 93.6 %, much higher than pure TiO₂ (48.2 %) in thecondition of middle or weak acidity. The decoloring ratio of organic montorillonite is the best (99.6 %) because of it's strong adsorption for organics. It can be recovered and reused owing to hydrophobicity.Nano-magnetic ferriferous oxide support:Titanium dioxide and ferriferous oxide are transition metal oxide. Their physical properties are similar and they can coexist. The core-shell magnetic nano-meter titanium dioxide/ferriferous oxide composite photocatalyst was prepared. The photoactive TiC>2 was deposited onto the surface of magnetic Fe3C>4 cores using acid sol method and homogenous precipitation coating technology. The morphological structure of the photocatalyst particles was characterized by XRD and TEM. The crystal of TiC>2 is anatase and the crystal size is 2.4³.6 nm. The composite particles with a size are 35-50 nm and 60-80 nm, respectively. The composite particle is larger than the particle using acid sol method. The photocatalyst shows the absorptive wavelength is red-shifted and the absorbance increases. The decolorization ratio of composite photocatalyst with acid sol (100 %) is higher than that of the homogenous precipitation (97.12 %).The advantages of composite photocatalyst with core-shell magnetic nano-meter is easily recovered and the material can be reused.Carbon nano-tube support:Carbon nano-tube (CNT) is a novel material accompanied by good electrical conductivity. It has greater surface area, atom-deficiency<> The nano-TiC^-CNT is prepared with acid sol method using tetrabutyl titanate as raw material. The crystal of nano-TiC?2 is anatase structure, and its crystal size is 4.2².5 nm. The crystal of T1O2 is smaller with the increase of CNT content for the composite catalysts. It shows that there is strong interaction between CNT and TiO2.The CNT-TiCVGC electrode is prepared using Nafion solution to immobilize CNT-TiO2 on glassy carbon electrode. The analysis method of photo-electrochemical catalysis was investigated. The adsorption process conforms to Langmuir adsorption law. Larger signal and higher sensitivity in the TiCh-CNT/GC electrode than those in the TiCVcarbon paste electrode means the TiCVCNT/GC electrode possesses betterphoto-electrochemical response.The research results prove that the nano-TiO2 can be immobilized on the surface of supports efficiently with structure stability and large surface area material as support. TiO2 has high active of nano-crystal and steady immobilization because of action between TiC>2 and support.It is an efficient route for semiconductor photocatalysis degradation becoming industrialization.