TiO2 Mole Ratio Research Articles

Enhancement of TiO2 activity under visible light by N,S codoping for Pb(II) removal from water

This paper deals with a systematic study on the co-doping N,S on TiO2 photocatalyst to improve its activity under visible light on the removal of Pb(II) from the aqueous media. The co-doping TiO2 by N,S atoms was conducted in an autoclave by one-step hydrothermal of TiO2 mixed with nitric and sulfuric acids as the sources of N and S, respectively. The mole ratio of TiO2:nitric acid:sulfuric acid was varied as 1:1:0.5, 1:1:1, and 1:1:1.5 to find the best ratio toward the activity. The co-doped photocatalysts obtained were characterized by specular reflectance UV/Vis (SRUV), X-ray diffraction (XRD), and fourier transform infrared (FTIR) instruments. A batch experiment was carried out for oxidation of Pb(II), driven by a combination of visible light and TiO2-N,S photocatalyst. The research results attribute that co-doping N,S into TiO2 has remarkably narrowed the gap in the TiO2 structure, emerging in the visible region. It was also proven that the co-doped in TiO2 can considerably enhance its activity in the removal of Pb(II) under visible light, and the highest activity was owned by TiO2-N,S (1:1:1). Furthermore, the most effective removal of Pb(II) 10 mg/L (98%) could be reached by employing 500 mg L-1 of the TiO2-N,S (1:1:1) dose, 45 min of the time, and the solution pH at 7. The Pb(II) removed is due to the photo-oxidation induced by OH radicals to form the handleable PbO2.

Production of titanium powder by metallothermic reduction of TiO2 in cold pressed pellets

In order to produce low-cost titanium (Ti) with high productivity, fundamental studies on producing metallic Ti from titanium dioxide (TiO2) in the cold pressed pellets were conducted by metallothermic reduction with an indirect contact method. This paper focuses on discussing the mechanism of the reduction process and the relationships of RM (a revised reduction index) with reduction temperature, reduction time, and mole ratio of TiO2 to CaCl2 ( $${n_{{\rm{Ti}}{{\rm{O}}_2}}}/{n_{{\rm{CaC}}{{\rm{l}}_2}}}$$ ) in the pellets. The results show that metallic Ti was obtained from the reduction of TiO2 in the pellets by calcium (Ca) vapor; pellets were reduced homogenously and Ca vapor diffused into the porous pellets by Knudsen diffusion or the mixing diffusion of molecular diffusion and Knudsen diffusion at 1273 K; RM increased with the increases of temperature and reduction time and was 96.34% when TRedu=1273 K, tRedu=6 h, and $${n_{{\rm{Ti}}{{\rm{O}}_2}}}/{n_{{\rm{CaC}}{{\rm{l}}_2}}} = 4$$ ; the reasonable nTiO2/nCaCl2 value is 3–5 for the pellets with enough strength and high RM.

High photocatalytic activity of TiO2/Fe2O3 nanocomposite prepared by impregnation method for degradation of indigo carmine

The photocatalytic degradation of indigo carmine (IC) dye was carried out by using TiO2/Fe2O3 nanocomposite prepared by impregnation method under UV light irradiation. The effect of TiO2 to Fe2O3 mole ratio on the properties and photocatalytic activity of TiO2/Fe2O3 nanocomposite was studied by the prepared three series of TiO2/Fe2O3 nanocomposites with TiO2 to Fe2O3 mole ratio of 1:3, 1:1 and 3:1. The characterization of TiO2/Fe2O3 nanocomposite by XRD showed that the iron (III) oxide extracted from iron ore and calcined at 700°C was in hematite phase (a-Fe2O3). The photocatalytic activity of TiO2/Fe2O3 nanocomposites was determined by using 6 W UV lamps with the wavelength 365 nm and the degradation efficiency of indigo carmine was determined based on UV-Vis spectrophotometer data. The TiO2/Fe2O3 nanocomposite with the the mole ratio of TiO2 to Fe2O3 1:3 showed higher photocatalytic activity than other mole ratio and bare Fe2O3. Degradation efficiency also was highly affected by the initial pH of IC solution, photocatalyst dosage and initial IC concentration. The maximum experimental degradation efficiency of IC was achived at pH value 1 using 0.35 g of photocatalyst and at 20 ppm of initial IC concentration after being irradiated by UV light for 120.

Stability Investigation of a Supported TiO2–Pd Bifunctional Catalyst over the One-Pot Liquid-Phase Synthesis of Methyl Isobutyl Ketone from Acetone and H2

The one-pot liquid-phase synthesis of methyl isobutyl ketone (MIBK) from acetone and H2 is a significant process in the fine-chemicals industry. In this paper, we fabricated a series of TiO2–SiO2/SiO2(F)&Pd/Cor bifunctional catalysts and optimized the ratio of TiO2 to SiO2 to be 1. The catalyst with the optimal mole ratio of TiO2 to SiO2 was further investigated in a long-term operation in a trickle-bed reactor, which delivered a stable MIBK selectivity of 83–93% at 26–36% acetone conversion for 300 h. The characterizations of Fourier transform infrared spectra, Raman spectra, thermogravimetric analysis, X-ray diffraction, X-ray photoelectron spectroscopy, temperature-programmed desorption of CO2 and NH3, and pyrolysis infrared spectra reveal that the active sites of acetone condensation and dehydrogenation could be attributed to the Ti–O–Si bonds. Deactivation of the catalyst resulted from a decrease of the active sites because of the aggregation of TiO2 and carbonaceous accumulation on the catalyst surface.

Preparation of TiO2/ZnO composite catalysts and their photocatalytic activity for degradation of pentachlorophenol

PurposeThis paper aims to report a novel preparation method of titanium dioxide (TiO2)/zinc oxide (ZnO) composites with different mole ratios of TiO2:ZnO and their photocatalytic activity.Design/methodology/approachTiO2/ZnO composites are prepared by a facile route. X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and ultra-violet–visible diffuse reflectance spectra (UV-vis DRS) are used to characterize the products. Photocatalytic activity of the samples is evaluated by degradation of persistent organic pollutant pentachlorophenol under ultra-violet (UV) irradiation.FindingsIt is found that all the as-prepared TiO2/ZnO composites not only have good catalytic activity under UV light irradiation, but also have excellent circulation stability. The optimal mole ratio of TiO2:ZnO is 0.75:1.Originality/valueThis report presents a simple and rapid method for the preparation of TiO2/ZnO composites with excellent photocatalytic activity. Experimental results could provide useful reference for the treatment of chlorophenols in the future.

Photoreduction of CO2 on TiO 2/SrTiO 3 Heterojunction Network Film.

Nanotube titanic acid (NTA) network film has a porous structure and large BET surface area, which lead them to possessing high utilization of the incident light and strong adsorption ability. We used NTA as the precursor to fabricate a TiO2/ SrTiO3 heterojunction film by the hydrothermal method. In the process of the reaction, part of NTA reacted with SrCl2 to form SrTiO3 nanocubes, and the remainder dehydrated to transform to the rutile TiO2. The ratio of TiO2 and SrTiO3 varied with the hydrothermal reaction time. SEM and TEM images indicated that SrTiO3 nanocubes dispersed uniformly on TiO2 film, and the particle size and crystallinity of SrTiO3 nanocubes increased with the reaction time prolonging. The TiO2/SrTiO3 heterojunction obtained by 1 h showed the best activity for CO2 photoreduction, where the mole ratio of TiO2 and SrTiO3 was 4:1. And the photo-conversion efficiency of CO2 to CH4 improved remarkably after the foreign electron traps of Pt and Pd nanoparticles were loaded. The highest photocatalytic production rate of CH4 reached 20.83 ppm/h cm2. In addition, the selectivity of photoreduction product of CO2 was also increased apparently when Pd acted as the cocatalyst on TiO2/SrTiO3 heterojunction film.

다양한 상용 TiO<sub>2</sub> 담체의 물리화학적 특성과 Ce/Ti 촉매의 SCR 반응활성과의 상관성 연구

Ceria supported on various commercial TiO2 catalysts were prepared by wet-impregnation method. We confirmed that the correlation between physicochemical properties of TiO2 supports and SCR activities. Physicochemical properties of the various TiO2 were evaluated using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area, X-ray photoelectron spectro- scopy (XPS), and pH analysis. Ce/Ti catalyst exhibited different SCR activities with respect to physicochemical properties of TiO2. An excellent activity was obtained as the surface area of TiO2 increased. In the case of CeOx surface density, the excellent activity in a range of 2.5∼14.5 CeOx/nm 2 was achieved and the activity tended to decrease above 14.5 CeOx/nm 2 . The O/Ti mole ratio of TiO2 in the range of 1.32 to 1.79 showed an excellent SCR activity. It was also confirmed that the pH of the TiO2 has no effects on the SCR activity. In order to achieve excellent SCR activities, ceria oxide should be sup- ported on TiO2 possessing a high specific surface area and certain O/Ti mole ratio. In addition, the catalyst with the low CeOx surface density resulted from the high dispersed ceria oxide should be prepared.

Efficient visible-light photocatalytic hydrogen evolution over platinum supported titanium dioxide nanocomposites coating up-conversion luminescence agent (Er3+:Y3Al5O12/Pt–TiO2)

In this work, a novel up-conversion luminescence agent (Er3+:Y3Al5O12) was synthesized by sol-gel method and then for visible-light photocatalytic hydrogen evolution a corresponding visible-light photocatalyst, platinum supported titanium dioxide nanocomposites coating up-conversion luminescence agent (Er3+:Y3Al5O12/Pt–TiO2 nanocomposite particles), was successfully prepared by sol-gel and calcination methods. Er3+:Y3Al5O12, Pt–TiO2 and Er3+:Y3Al5O12/Pt–TiO2 were all characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM) and energy dispersive X-ray spectroscopy (EDX). The visible-light photocatalytic activity of Er3+:Y3Al5O12/Pt–TiO2 nanocomposites was examined through photocatalytic hydrogen evolution from methanol splitting under visible-light irradiation. The influence factors such as Er3+:Y3Al5O12 and Pt–TiO2 mole ratio, heat-treated temperature and heat-treated time on the visible-light photocatalytic hydrogen evolution activity of Er3+:Y3Al5O12/Pt–TiO2 nanocomposites were also studied. Particularly, Er3+:Y3Al5O12/Pt–TiO2 nanocomposites with 1.5:1.0 M ratio heat-treated at 500 °C for 60 min showed the highest visible-light photocatalytic activity in hydrogen evolution from methanol splitting.

Pure ZnO and composite ZnO/TiO2 catalyst plates: A comparative study for the degradation of azo dye, pesticide and antibiotic in aqueous solutions

Photocatalytic degradations of azo dye (RR 180), pesticide (2,4-D) and antibiotic (enrofloxacin) in aqueous solutions were performed and compared by using pure ZnO and ZnO/TiO2 composite (at 1:1 ZnO to TiO2 mole ratio) catalysts in a self-supporting plate form. The plates were produced by tape casting of the constituent powder slurries and sintering at 600°C. Photocatalytic degradations of these pollutants were carried out under UVA and UVC irradiations for 120min. Maximum degradation was obtained for 2,4-D solution using pure ZnO plates under UVC. Due to the photolysis effect, UVC wavelength yielded higher efficiency values for all the chemicals than UVA. The discrepancy in the photocatalytic performances of the pure ZnO and the ZnO/TiO2 composite plates were not found to be significant. The plates were found to be effective for the consecutive degradation tests which indicated their potentiality in extended applications.

Visible-light photocatalytic activity of Pt supported TiO2 combined with up-conversion luminescence agent (Er3+:Y3Al5O12) for hydrogen production from aqueous methanol solution

In this paper, a high effective up-conversion luminescence agent (Er3+:Y3Al5O12) is synthesized by sol–gel method, and then its corresponding visible-light photocatalyst (Er3+:Y3Al5O12/Pt–TiO2) is successfully prepared by direct mixing and calcination methods. For comparison, Er3+:Y3Al5O12, Pt–TiO2 and Er3+:Y3Al5O12/Pt–TiO2 are all characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). At first, the up-conversion luminescence properties of Er3+:Y3Al5O12 are reviewed by excitation spectrum in visible-light region and emission spectrum in ultraviolet-light region. And then, under visible-light irradiation the visible-light photocatalytic activity of Er3+:Y3Al5O12/Pt–TiO2 is examined through photocatalytic hydrogen production from aqueous methanol solution. Lastly, the influence factors such as Er3+:Y3Al5O12 and Pt–TiO2 mole ratio, heat-treated temperature and heat-treated time on the visible-light photocatalytic hydrogen production activity of Er3+:Y3Al5O12/Pt–TiO2 are studied. Particularly, Er3+:Y3Al5O12/Pt–TiO2 with 6:100 M ratio heat-treated at 550 °C for 90 min shows the highest photocatalytic activity in hydrogen production from aqueous methanol solution.

N-TiO<SUB>2</SUB>/<I>γ</I>-Al<SUB>2</SUB>O<SUB>3</SUB> Granules: Preparation, Characterization and Photocatalytic Activity for the Degradation of 2,4-Dichlorophenol

Nitrogen doping TiO2 and gamma-Al2O3 composite oxide granules (N-TiO2/gamma-Al2O3) were prepared by co-precipitation/oil-drop/calcination in gaseous NH3 process using titanium sulphate and aluminum nitrate as raw materials. After calcination at 550 degrees C in NH3 atmosphere, the composite granules showed anatase TiO2 and gamma-Al2O3 phases with the granularity of 0.5-1.0 mm. The anatase crystallite size of composite granules was range from 3.5-25 nm calculated from XRD result. The UV-Vis spectra and N 1s XPS spectra indicated that N atoms were incorporated into the TiO2 crystal lattice. The product granules could be used as a photocatalyst in moving bed reactor, and was demonstrated a higher visible-light photocatalytic activity for 2,4-dichlorophenol degradation compared with commercial P25 TiO2. When the mole ratio of TiO2 to Al2O3 equal to 1.0 showed the highest catalytic activity, the degradation percentage of 2,4-chlorophenol could be up to 92.5%, under 60 W fluorescent light irradiation for 9 hours. The high visible-light photocatalytic activity might be a synergetic effect of nitrogen doping and the form of binary metal oxide of TiO2 and gamma-Al2O3.

Studies on Structural, Microwave Dielectric Properties, and Low-Temperature Sintering of 1.52Li<sub>2</sub>O-0.36Nb<sub>2</sub>O<sub>5</sub>-1.34TiO<sub>2</sub> Ceramic

The structure, microwave dielectric properties and low-temperature sintering of a new Li2O-Nb2O5-TiO2 system ceramic with the Li2O: Nb2O5: TiO2 mole ratio of 1.52: 0.36: 1.34 have been investigated in this study. The 1.52Li2O-0.36Nb2O5-1.34TiO2 (LNT) ceramic is composed of two phases, the “M-Phase” and Li2TiO3 solid solution (Li2TiO3ss) phase. This new microwave dielectric ceramic has low intrinsic sintering temperature ( ~ 1100 oC ) and good microwave dielectric properties of middle permittivity (εr ~38.6), high Q×f value up to 7712 GHz, and near zero τf value (~ 4.64 ppm/oC). In addition, the sintering temperature of the LNT ceramics could be lowered down effectively from 1100 oC to 900 oC by adding 1 wt.% B2O3. Good microwave dielectric properties of εr = 42.5, Q*f =6819 GHz and τf = 2.7 ppm/oC could be obtained at 900 oC, which indicate the ceramics would be promising candidates for low-temperature co-fired ceramics (LTCC) applications.

Photoconductivity and trap-related decay in porous TiO2/ZnO nanocomposites

Photoconductivity and trap-related decay were investigated in porous TiO2/ZnO nanocomposites. Photoconductivity responses of TiO2 and ZnO were completely different, which were attributed to electron-scavenging effect and hole trapping effect, respectively. When the mole ratio of TiO2:ZnO was from 9:1 to 6:4, the photoconductivity responses were consistent with TiO2. On the contrary, when the mole ratio of TiO2:ZnO was from 4:6 to 1:9, the photoconductivity responses were controlled by ZnO. Time constants were obtained by fitting the experiment data with an exponential function. We found that they tended to get larger with the percentage of ZnO while a turning point appeared at TiO2:ZnO = 1:9. The pattern was assigned to different carrier trapping mechanisms as well as carrier separation. Composition effect was defined by a quantitative formula to evaluate the recombination processes of composite materials. A mechanism was proposed to explain this phenomenon.

Microwave dielectric properties of the 5.5Li2O–Nb2O5–7TiO2 ceramics

A new Li2O–Nb2O5–TiO2 (LNT) ceramic with the Li2O:Nb2O5:TiO2 mole ratio of 5.5:1:7 was prepared by solid state reaction route. The phase and structure of the ceramic were characterized by X-ray diffraction and scanning electron microscopy (SEM). The microwave dielectric properties of the ceramics were studied using a network analyzer. The microwave dielectric ceramic has low sintering temperature (∼1075°C) and good microwave dielectric properties of er=42, Q×f=16900 GHz (5.75 GHz), and τf=63.7 ppm/°C. The addition of B2O3 can effectively lower the sintering temperature from 1075 to 875°C and does not induce degradation of the microwave dielectric properties. Obviously, the LNT ceramics can be applied to microwave low temperature-cofired ceramics (LTCC) devices.

Microwave dielectric properties of 3Li2O–Nb2O5–3TiO2 ceramics with Li2O–V2O5 additions

A new Li2O–Nb2O5–TiO2 (LNT) ceramic with the Li2O:Nb2O5:TiO2 mole ratio of 3:1:3 has been investigated. The compound is composed of two phases, the Li2TiO3 and “M-phase” solid solution phase. The microwave dielectric ceramic has low sintering temperature (∼1100 °C) and good microwave dielectric properties of a relatively high permittivity (∼51), high Q × f value up to 8700, and small temperature coefficient (∼37 ppm/°C). The low-amount doping of 0.83Li2O–0.17V2O5 (LV) can effectively lower the sintering temperature from 1100 to 900 °C and induce no obvious degradation of the microwave dielectric properties. Typically, the 1 wt.% LV-doped ceramic sintered at 900 °C has better microwave dielectric properties of er = 51.3, Q × f = 7235 GHz, τf = 22 ppm/°C, which suggests that the ceramics can be applied in microwave LTCC devices.

Photocatalytic Activities for Carbon Dioxide Reduction of TiO2Microcrystals Prepared in SiO2Matrices Using a Sol–Gel Method

The size of TiO2 microcrystals embedded in SiO2 matrices, which were prepared using a mixed sol of TiO2 and SiO2 in ethanol, decreased with a decrease of the mole ratio of TiO2 to SiO2 in the sol. The prepared TiO2 microcrystals showed activities for photoreduction of CO2 to formate, methane and ethylene, and the quantum efficiencies for the production of these were increased with decreasing the size of the TiO2 microcrystals.

Crystallization of Glasses Containing BaO and TiO<sub>2</sub>

In order to make barium titanate ceramics having high dielectric constant by a process of crystallization of glass, a series of glasses with the general composition (100-x-y) BaO⋅TiO2+xSiO2+yAl2O3, in which x and y are within the range of 10 to 60 and 0 to 20 mole per cent, respectively, was investigated, especially with respect to their glass formation tendencies, crystallization behaviors during reheating and dielectric properties of their crystallized products.The glasses were melted, in all cases, in platinum crucibles at 1450°C for one hour and formed into plate of about 2mm thick. They were crystallized by reheating up to 1100°C at a rate of 5°C/min.The results of the experiments are summerized as follows:1) A glass formation region was determined (cf. Fig. 1).2) In general, crystallization of the glasses in this region starts at about 850°C, and is almost completed at 1100°C (cf. Fig. 3 and 5). The resulting crystallized products show flaws such as cracks and surface unevenness when the parent glasses contain BaO⋅TiO2 or Al2O3 in excess (cf. Fig. 2).3) Major constituents of the crystallized products are BaTiO3 (tetragonal), BaAl2Si2O8 (hexagonal), BaTiSiO5 and some unidentified crystalline phases (cf. Table 2).4) For the crystallized products with Al2O3 held constant, their dielectric constant decreases with increasing the SiO2/BaO⋅TiO2 mole ratio. For those with BaO⋅TiO2 held constant, it reaches a maximum when the Al2O3/SiO2 mole ratio is set to 35/65 (cf. Fig. 7). Generally, it increases with increasing the amount of barium titanate crystals separated out in the crystallized products. The composition of the crystallized product which shows a maximum dielectric constant (about 500 at 106c) in the present experiments is BaO⋅TiO2 60, SiO2 26, Al2O3 14 mole per cent.5) On the basis of Bruggeman's theory the crystallized products obtained were assumed to have the structure of prophyritic mixture in which lamellar barium titanate crystals are dispersed in matrix consisting of glass phase and crystal phases of BaAl2Si2O8 and BaTiSiO5 etc. (cf. Fig. 8).

Effect of BaO, TiO<sub>2</sub> Mole Ratio on the Remanent Polarization and Dielectric Properties of BaTiO<sub>3</sub> Ceramics

Barium titanate ceramics were prepared in laboratory in order to know how the remanent polarization and dielectric properties of BaTiO3 ceramic elements were effected by firing temperature and BaO, TiO2 mole ratio used making BaTiO3.Test pieces were prepared from the lots in which BaO, TiO2 mol ratio were changed from 0.990:1.000 to 1.020:1.000, and fired to the temperature ranging from 1350°C to 1460°C.The results obtained may be summarized as follows. (1) In general, bodies deficient TiO2 gave the test disks with increasing abnormal polarization phenomenon and dielectric loss (2) BaTiO3 ceramics of 1 mole % excess TiO2 did not show the abnormal polarization pheomenon, but the test pieces of decreasing more or less the total remanent polarization. (3) It was found that the abnormal polarization phenomenon resulted from the remains of hexagonal BaTiO3 or Ba2TiO4, BaTi4O9, etc.