Experimental studies on photocatalytic oxidation of nitric oxides using titanium dioxide

In order to remove nitric oxides （NO） from flue gas, experimental studies on the photocatalytic oxidation （PCO） of NO are carried out in an efficient laboratory-scale reactor. Nano-sized TiO2 particles loading on quartz sand are prepared and used as the photocatalyst. Effects of several key operating parameters on NO conversion are investigated, including operating temperature, NO inlet concentration, oxygen percentage, relative humidity and residence time. The results illustrate that the NO inlet concentration, the oxygen percentage and the relative humidity play an important role in the oxidation of NO. A lower NO inlet concentration and a higher oxygen percentage result in a higher NO conversion efficiency. When the relative humidity is 8%, the maximum value of NO conversion efficiency is achieved. In addition, the operating temperature and the residence time have a little effect on the conversion efficiency of NO.

Preparation, Characterization and Photocatalytic Activity of Fe, La Co-doped Nanometer Titanium Dioxide Photocatalysts

A series of photocatalysts of un-doped, single-doped and co-doped nanometer titanium diox- ide （TiO2） have been successfully prepared by template method using Fe（NO3）3.9H2O, La（NO3）3.6H2O, and tetrabutyl titanate as precursors and glucan as template. Scanning electron microscopy, X-ray diffraction, and N2 adsorption-desorption measurement were employed to characterize the morphology, crystal structure and surface structure of the samples. The photo-absorbance of the obtained catalysts was measured by UV-Vis absorption spectroscopy, and the photocatalytic activities of the prepared samples under UV and visible light were estimated by measuring the degradation rate of methyl orange in an aqueous solution. The characterizations indicated that the prepared photocatalysts consisted of anatase phase and possessed high surface area of ca. 163-176 m2/g. It was shown that the Fe and La co-doped nano-TiO2 could be activated by visible light and could thus be used as an effective catalyst in photo-oxidation reactions. The synergistic effect of Fe and La co-doping played an important role in improving the photocatalytic activity. In addition, the possibility of cyclic usage of co-doped nano-TiO2 was also confirmed, the photocatalytic activity of codoped nano-TiO2 remained above 89.6% of the fresh sample after being used four times.

Preparation, Characterization and Photocatalytic Activity of Lanthanum Doped Mesoporous Titanium Dioxide

Lanthanum doped mesoporous titanium dioxide photocatalysts with different La content were synthesized by template method using tetrabutyltitanate （Ti（OC4H9）4） as precursor and Pluronic P123 as template. The catalysts were characterized by thermogravimetric dif ferential thermal analysis, N2 adsorption-desorption measurements, X-ray diffraction, and UV-Vis adsorption spectroscopy. The effect of La3＋ doping concentration from 0.1% to 1% on the photocatalytic activity of mesoporous TiO2 was investigated. The characterizations indicated that the photocatalysts possessed a homogeneous pore diameter of about 10 nm with high surface area of 165 m2/g. X-ray photoelectron spectroscopy measurements in- dicated the presence of C in the doped samples in addition to La. Compared with pure mesoporous TiO2, the La-doped samples extended the photoabsorption edge into the visible light region. The results of phenol photodecomposition showed that La-doped mesoporous TiO2 exhibited higher photocatalytic activities than pure mesoporous TiO2 under UV and visible light irradiation.

REMOVAL OF ORGANIC POLLUTANTS USING TITANIUM DIOXIDE MEDIATED PHOTOCATALYTIC OXIDATION

A simple and effective method of removing polluted organics in water is reported here.Titanium dioxide is a catalyst in photo-oxidation of monocrotophos.The mechanism of photocatalytic oxidation and the kinetics of the reaction were studied. This same principle also leads to the construction of instrument of PTR-FIA analysis for monitoring organic phosphorus and phosphate in water.

Photocatalytic degradation of Chicago Sky Blue 6B and Benzopurpurin 4B using titanium dioxide thin film

Aqueous solutions of azo dyes undergo degradation to form harmless intermediates and colorless products following irradiation by visible light in the presence of titanium dioxide thin films. The dyes that were studied in this work are： Chicago Sky Blue 6B and Benzopurpurin 4B. Results obtained indicated that complete mineralization of the dyes took place under the experimental conditions. There was an increase in conductivity after the complete mineralization experiments possibly indicating the formation of ions such as NO3^- and SO4^2-. Chemical oxygen demand（COD） measurements show a decrease in organic matter for both dyes following complete degradation. The effect of how changing experimental conditions such as pH, temperature and starting concentrations of dyes affected the rate of dye degradation was measured. There was an increase in the rate of disappearance of the dye color at lower pH. High concentrations of dye solutions reauired Iona dearadation time.

MoS_3 loaded TiO_2 nanoplates for photocatalytic water and carbon dioxide reduction

Photocatalytic water splitting and carbon dioxide reduction provide us clean and sustainable energy resources. The carbon dioxide reduction is also the redemption of the greenhouse effect. MoS/TiOphotocatalysts based on TiOnanoplates have been synthesized via a hydrothermal acidification route for water and carbon dioxide reduction reactions. This facile approach generates well dispersed Mo S3 with low crystallinity on the surface of TiOnanoplates. The as-synthesized MoS/TiOphotocatalyst showed considerable activity for both water reduction and carbon dioxide reduction. The thermal treatment effects of TiO, the loading percentage of MoSand the crystalline phase of TiOhave been investigated towards the photocatalytic performance. TiOnanoplate synthesized through hydrothermal reaction with the presence of HF acid is an ideal semiconductor material for the loading of MoSfor photocatalytic water and carbon dioxide reduction simultaneously in EDTA sacrificial solution.

Disruption of Bacterial Cells by Photocatalysis of Montmorillonite Supported Titanium Dioxide

The photo-induced antibacterial capacity of montmorillonite supported titanium dioxide （TiO2/Mmt for short） was evaluated by using Escherichia coli and Staphylococcus aureus as modal organims. The bactericidal activity of TiO2/Mmt was examined by cell viability assay under different illumination modes. Atomic force microscopy （AFM） and total organic carbon/Total nitrogen （TOC/TN） analyses were employed to investigate the mechanism of the photocatalytic bactericidal process qualitatively and quantitatively. The kinetic data show that TiO2/Mmt has excellent antibacterial performance, and about 99% of both bacteria cells are inactivated within 75 rain illumination. The AFM images demonstrate that the bacterial cells are irreversibly decomposed and some cell components are dissolved. Therefore, the content and phase of carbon and nitrogen in the solution are changed after photocatalytic reaction.

Enhanced Photoactivity of Layered Nanocomposite Materials Containing Rare Earths,Titanium Dioxide and Clay

The nanocomposite materials containing rare earths, titanium dioxide and clay (RE/TiO2/Clay) were characterized and tested for the photocatalytic decomposition of formaldehyde. The results show that nanocomposite materials prepared by doping appropriate rare earth elements have better photocatalytic properties than that prepared by doping excessive rare earth elements. The photocatalytic mechanism of composite materials was studied by integrating the theory of pho-tocatalysis with experiment results. Because the site of photocatalytic reaction was limited in the interspace of clay, photocatalytic reaction occurred by two steps: firstly, organic molecules dispersed into the interlayers of clay; secondly, organic molecules and photocatalyst of RE/TiO2 occurred photocatalytic reaction, resulting in forming carbon dioxide.

Facile synthesis of Ag_2O-TiO_2/sepiolite composites with enhanced visible-light photocatalytic properties

Ag2O-TiO 2/sepiolite heterostructure composites were synthesized by a simple two-step method at low temperatures（100–450 °C）. Acid red G aqueous solution and gaseous formaldehyde were chosen as model organic pollutants to evaluate the photocatalytic performance of the as-prepared composites. The results showed that the Ag2O-TiO 2/sepiolite exhibited enhanced photocatalytic activity over pure Ag2O-TiO 2,TiO 2/sepiolite,and Ag2O/sepiolite under visible-light irradiation（λ 420 nm）. The excellent photocatalytic efficiency of these composites can be ascribed to the synergistic effect between the heterojunction and the porous structure of the clay layers,which induced high adsorption and efficient charge separation. In addition,the active species involved in the degradation reaction have been investigated by photoluminescence spectroscopy and quenching experiments. A possible photocatalytic degradation mechanism of acid red G dye by the Ag2O-TiO 2/sepiolite composite is also discussed.

Strong visible absorption and excellent photocatalytic performance of brown TiO_2 nanoparticles synthesized using one-step low-temperature process

particle size （5.0 nm）, large specific surface area （213.45 m1 2/g）, and efficient response to broadband light over the entire ultraviolet-visible spectrum with a narrow band gap of 1.84 eV. In addition, TiO2 -180℃ exhibited the optimal reaction rate constant for the degradation of methylene blue （0.08287 mg/（Lmin））, which is six times higher than that of the mixed rutile/anatase phase TiO2 photocatalytic standard P25 （0.01342 mg/（L min））. Furthermore, cycling photodegradation ex-periments confirmed the stability and reusability of this catalyst. The unique physicochemical properties resulting from the low-temperature preparation of TiO2 -180℃, including its broadband visible absorption associated with a high concentration of oxygen vacancies, large surface area, and enriched surface -OH/H2O may be responsible for this excellent photocatalytic performance. The use of as-prepared TiO2 -180℃ for practical applications is expected after further optimization.

Photocatalytic Degradation of Phenol over MWCNTs-TiO2 Composite Catalysts with Different Diameters

Titania-based composite catalysts were prepared through a sol-gel route employing multi-walled carbon nanotubes with different diameters. The materials were characterized using thermogravimetric analysis, nitrogen adsorption-desorption isotherm, powder X-ray diffraction, scanning electron microscopy, and diffuse reflectance UV-Vis absorption spectra. The application of the catalysts to photocatalytic degradation of phenol was tested under UV-Vis irradiation. A synergetic effect on phenol removal was observed in case of composite catalysts, which was evaluated in terms of apparent rate constant, total organic carbon removal and photonic efficiency.

Novel visible-light-responding InVO_4-Cu_2O-TiO_2 ternary nanoheterostructure: Preparation and photocatalytic characteristics

A novel visible-light-responding InVO4-Cu2O-TiO2 ternary nanoheterostructure was designed on the basis of the strategy of energy gap engineering and prepared through ordinary wet chemistry methods. The as-prepared nanoheterostructure was characterized by X-ray powder diffraction（XRD）, transmission electron microscopy（TEM）, high-resolution transmission electron microscopy（HRTEM） and diffuse reflectance ultraviolet-visible spectroscopy（UV-vis/DRS）. The TEM and HRTEM images of 10%InVO4-40%Cu2O-50%TiO2 confirm the formation of nanoheterostructures resulting from contact of the nanosized TiO2, Cu2O and InVO4 in the size of 5–20 nm in diameter. The InVO4-Cu2O-TiO2 nanoheterostructure, when compared with TiO2, Cu2O, InVO4, InVO4-TiO2 and Cu2O-TiO2, shows significant enhancement in the photocatalytic performance for the degradation of methyl orange（MO） under visible-light irradiation. With a 9 W energy-saving fluorescent lamp as the visible-light source, the MO degradation rate of 10%InVO4-40%Cu2O-50%TiO2 reaches close to 90% during 5 h, and the photocatalytic efficiency is maintained at over 90% after six cycles. This may be mainly ascribed to the matched bandgap configurations of TiO2, Cu2O and InVO4, and the formations of two p-n junctions by the p-type semiconductor Cu2O with the n-type semiconductors TiO2 and InVO4, all of which favor spatial photogenerated charge carrier separation. The X-ray photoelectron spectroscopy（XPS） characterization for the used 10%InVO4-40%Cu2O-50%TiO2 reveals that only a small shakeup satellite peak appears for Cu（II） species, implying bearable photocorrosion of Cu2O. This work could provide new insight into the design and preparation of novel visible-light-responding semiconductor composites.

Photocatalytic Activity of Hierarchical Flower-Like TiO_(2) Superstructures with Dominant {001} Facets

The fabrication of well defined hierarchical structures of anatase TiO_(2) with a high percentage of reactive facets is of great importance and challenging.Hierarchically flower-like TiO_(2) superstructures(HFTS)self-assembled from anatase TiO_(2) nanosheets with exposed{001}facets(up to 87%)were synthesized by a simple alcohothermal strategy in a HF-H_(2)O-C_(2)H_(5)OH mixed solution using titanate nanotubes as precursor.The samples were characterized by X-ray diffraction,scanning electron microscopy,transmission electron microscopy,and N2 adsorption-desorption isotherms.The photocatalytic activity was evaluated by the photocatalytic oxidation decomposition of acetone in air and methyl orange in aqueous solution under UV illumination.The photocatalytic activity of HFTS was much higher than that of commercial Degussa P25 and tabular-shaped anatase TiO_(2) obtained using pure water as the synthesis medium.The enhancement in photocatalytic activity was related to several factors,including the hierarchically porous structure,exposed{001}facets,and increased light harvesting ability.The HFTS was also of interest for use in solar cells,photocatalytic H_(2) production,optoelectronic devices,sensors,and catalysis.

Synthesis and photocatalytic properties of lanthanum doped anatase TiO_2 coated Fe_3O_4 composites

A composite photocatalyst （La/TiO2/Fe3O4） with a lanthanum doped TiO2 （La/TiO2） shell and a magnetite core was prepared by coating photoactive La/TiO2 onto a magnetic Fe3O4 core. The morphological, structural, and optical properties of as-prepared samples were charac-terized by transmission electron microscopy （TEM）, X-ray diffraction （XRD） and UV-vis absorption spectroscopy. The effect of lanthanum content on the photocatalytic properties was studied, and the result revealed that 0.15 mol% La/TiO2/Fe3O4 exhibited the highest photoactiv-ity. The photocatalytic properties of the prepared photocatalyst under UV and visible light were investigated in aqueous solution using methyl orange （MO） as a target pollutant. The results showed that the prepared photocatalyst was activated by visible light and used as an ef-fective catalyst in photooxidation reactions. In addition, the possibility of cyclic usage of the prepared photocatalyst was also confirmed. Moreover, La/TiO2 was tightly bound to Fe3O4 and could be easily recovered from the medium by a simple magnetic process.

Preparation of nano-TiO_2/diatomite-based porous ceramics and their photocatalytic kinetics for formaldehyde degradation

Diatomite-based porous ceramics were adopted as carriers to immobilize nano-TiO2 via a hydrolysis-deposition technique. The thermal degradation of as-prepared composites was investigated using thermogravimetric-differential thermal analysis, and the phase and microstructure were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electron microscopy. The results indicated that the carriers were encapsulated by nano-TiO2 with a thickness of 300-450 nm. The main crystalline phase of TiO2 calcined at 650~C was anatase, and the average grain size was 8.3 nm. The FT-IR absorption bands at 955.38 cm1 suggested that new chemical bonds among Ti, O, and Si had formed in the composites. The photocatalytic （PC） activity of the composites was investigated un- der UV irradiation. Furthermore, the photodegradation kinetics of formaldehyde was investigated using the composites as the cores of an air cleaner. A kinetics study showed that the reaction rate constants of the gas-phase PC reaction of formaldehyde were k = 0.576 mg＇m3·min^-1 and K = 0.048 m3/mg.

Enhanced photocatalytic activity of (La, N) co-doped TiO_2 by TiCl_4 sol-gel autoigniting synthesis

（La, N） co-doped TiO2 photocatalysts were synthesized using TiC14 sol-gel autoignidng synthesis （SAS） starting from a complex compound system of TiCl4-La（NO3）3-citric acid-NH4NO3-NHyH2O, in which the （La, N） co-doped process was accompushed in the formation of TiO2 nanocrystals. The prepared samples were characterized by using X-ray diffraction （XRD）, X-ray photoemission spectroscopy （XPS） and UV-vis diffuse reflectance spectra. The results indicated that nitrogen and lanthanum were incorporated into the lattice and interstices of titania nanocrystals, which resulted in narrowing the band gap and promoting the separation of photoexcited hole-electron pairs, respectively, and showing expected red-shifts and enhanced photocatalytic activity under visible light. The mechanism on nitrogen doping and enhancement in photocatalyfic activity of （La, N） co-doped titania by SAS was discussed in detail.

Direct fabrication of highly porous graphene/TiO_2 composite nanofibers by electrospinning for photocatalytic application

We reported the fabrication of highly porous graphene/TiO2 composite nanofibers in the form of a nonwoven mat by electrospinning followed by calcination in air at 450°C.The graphene can uniformly disperse in highly porous TiO2 nanofibers.The highly porous graphene/TiO2 composite nanofibers exhibited excellent catalytic activities.The new method for producing graphene/TiO2 composite nanofibers is versatile and can be extended to fabricate various types of metal oxide and graphene nanocomposites.

Photocatalytic degradation of MO by complex nanometer particles WO_3/TiO_2

Complex nanometer particles WO3/TiO2 were prepared using a sol-gel process and characterized using XRD spectra. The photocatalytic activity of TiO2 can be increased by doping W^6＋ with TiO2 because the doped W^6＋ that entered into the crystal lattices of TiO2 led to the formation of defects in the crystal lattices of TiO2 and thereby improved the photocatalytic activity of TiO2.When WO3 doped in TiO2 exceeded 3%, the excess W^6＋ did not enter into the crystal lattices of TiO2 but were uniformly dispersed in TiO2 or they covered the surface of TiO2, which reduced the effective illumination area of TiO2 and thereby lowered the photocatalytic activity of TiOE.The relationship among the composition of the catalyst, the amount of photocatalyst, the illumination time, and the decolorizing rate of methyl orange （MO） were discussed. The results show that the decolorizing rate of MO can reach 82.3% using WO3/TiO2 as the photocatalyst, with the composition of WO3/TiO2 -3：97, the mass of catalyst = 0.400 g, the initial concentration of MO = 20 mg/L, pH = 6.5, and the illumina- tion time = 7 h.

Synthesis of Bimodal Mesoporous TiO_(2)-PTA/BMMS and Its Enhanced Performance in the Photocatalytic Oxidative Desulfurization

With the bimodal mesoporous silica(BMMS)acting as the support and the composite of TiO2 with phosphotungstic acid(PTA)functioning as the active constituent,TiO_(2)-PTA/BMMS was synthesized by the two-step impregnation route.This catalyst was applied in the photocatalytic oxidative desulfurization(PODS)process,with dibenzothiophene serving as the model sulfur compound.PODS proceeds in one pot,in which H_(2)O_(2) acts as the oxidant and methanol plays the role of the solvent.TiO_(2)-PTA/BMMS was characterized by XRD,N_(2) adsorption and desorption,XRF,FTIR,UV-vis,SEM,EDS and TEM techniques.It showed that the introduction of PTA contributes higher order,higher surface area and pore volume to the bimodal mesoporous support.With TiO_(2)-PTA/BMMS used as the catalyst under the UV irradiation,the desulfurization rate can reach 99.6%.This result is obviously higher than that achieved by TiO_(2)/BMMS.The catalyst also has no significant drop in catalytic activity after eight runs of reusing.In such catalytic system,the synergistic effects of this photocatalytic oxidation and the extraction with the methanol serving as the solvent played an indispensable role.

Template-free synthesis of hollow TiO2 nanospheres supported Pt for selective photocatalytic oxidation of benzyl alcohol to benzaldehyde

Heterogeneous photocatalytic system are widely applied to degrade organic pollutants or converse into high value-added chemicals. Both environmental and energy aspects should be considered to improve these chemical processes, favoring reaction conditions that involve room temperature and ambient O2 pressure. In the present work, hollow titanium dioxide nanospheres were fabricated via template-free method. The prepared samples were characterized by X-ray diffraction, N2 adsorption–desorption isotherms, transmission electron microscopy, and X-ray photoelectron spectroscopy. The photocatalytic activity was evaluated by photocatalytic oxidation of benzyl alcohol to benzaldehyde with visible light under atmospheric pressure at room temperature. The designed hollow structure(2%Pt–TiO2–5) not only exhibited a very high surface area,but also promoted photonic behavior and multiple light scattering, which as an efficient photocatalyst performed moderate conversion(about 20%) and high selectivity(> 99%) for oxidation of benzyl alcohol to benzaldehyde at room temperature with visible light in solvent of toluene.This work suggests that both hollow structure and Pt nanoparticles have great potential for execution of oxidative transformations under visible light.