TiO2 Loading Research Articles

Photocatalytic Template Removal by Non-Ozone-Generating UV Irradiation for the Fabrication of Well-Defined Mesoporous Inorganic Coatings.

The processing of mesoporous inorganic coatings typically requires a high-temperature calcination step to remove organic precursors that are essential during the material assembly. Lowering the fabrication energy costs and cutting back on the necessary resources would provide a greater scope for the deployment in applications such as architectural glass, optical components, photovoltaic cells, and energy storage, as well as further compatibilize substrates with low temperature stability. Organic removal methods based on UV–ozone treatment are increasing in popularity, but concerns remain regarding large-scale ozone generation and usage of mercury-containing UV lamps. To this end, we present a method that relies on non-ozone-generating UV radiation at 254 nm (UV254) and incorporation of small amounts of photocatalytic material in the formulation, here demonstrated with TiO2 nanocrystals. At concentrations as low as 5 wt % relative to the main inorganic aluminosilicate material, the TiO2 nanocrystals catalyze a “cold combustion” of the organic components under UV254 irradiation to reveal a porous inorganic network. Using block copolymer-based co-assembly in conjunction with photocatalytic template removal, we produce well-defined mesoporous inorganic thin films with controlled porosity and refractive index values, where the required processing time is governed by the amount of TiO2 loading. This approach provides an inexpensive, flexible, and environmentally friendly alternative to traditional organic removal techniques, such as UV–ozone degradation and thermal calcination.

Photothermal catalytic effect of Pd-TiO2/CNFs composite catalyst in Suzuki coupling reaction

This paper reported a method for loading TiO2 and Pd atoms onto carbon nanofibers (CNFs) under a simple mild conditions. The catalyst prepared by the method greatly improved the reaction efficiency of Suzuki under the illumination of xenon lamp and reduced the difficulty of the reaction conditions. Compared with the previous catalysts, the catalysts developed in this paper have the characteristics of simple preparation method, easy recovery, good reaction performance, etc. The use of light energy reflected the importance of the catalyst in terms of resource utilization and environmental protection.

Reaction kinetics of mesotrione removal catalyzed by TiO2 in the presence of different electron acceptors

Many parameters influence the reaction kinetics of photocatalytic degradation of organic pollutants and their effects need to be evaluated. In this work, a full factorial experimental design was used to study the main parameter effects in detail and their interactions on the kinetics of mesotrione removal using TiO2 Hombikat (TiO2) suspension under simulated sunlight. The parameters which affect the efficiency of mesotrione photocatalytic degradation such as the loading of TiO2, concentration of KBrO3, absence/presence of fullerenol (FNP), as well as O2 purging were investigated. The photocatalytic degradation efficiency of mesotrione (%) in the range from 43.3 to 96.7% and apparent rate constants (kapp), obtained by exponential fitting, in the range from 1.849 × 10−2 min−1 to 6.228 × 10−2 min−1 with coefficient of determination ~ 0.99 are used as responses. From the statistical analysis in the case of both responses, the highest influence on the system has parameter loading of TiO2. The highest percentage of mesotrione removal was achieved with all parameters at high level, while the highest value of kapp was obtained under the same experimental conditions but in the absence of fullerenol.

Hydrogen Production from Glycerol Photoreforming on TiO2/HKUST-1 Composites: Effect of Preparation Method

Coupling metal-organic frameworks (MOFs) with inorganic semiconductors has been successfully tested in a variety of photocatalytic reactions. In this work we present the synthesis of TiO2/HKUST-1 composites by grinding, solvothermal, and chemical methods, using different TiO2 loadings. These composites were used as photocatalysts for hydrogen production by the photoreforming of a glycerol-water mixture under simulated solar light. Several characterization techniques were employed, including X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), infrared spectroscopy (FTIR), and time-resolved microwave conductivity (TRMC). A synergetic effect was observed with all TiO2/HKUST-1 composites (mass ratio TiO2/MOF 1:1), which presented higher photocatalytic activity than that of individual components. These results were explained in terms of an inhibition of the charge carrier (hole-electron) recombination reaction after photoexcitation, favoring the electron transfer from TiO2 to the MOF and creating reversible Cu1+/Cu0 entities useful for hydrogen production.

Photocatalytic degradation performance of La3+/Y3+/Eu3+ co-doped TiO2 loading on nickel foam

The band structure of TiO2 nanoparticles doped with La3+, Y3+ and Eu3+ rare earth ions, respectively, was calculated by CASTEP inmaterials Studio software. La3+/Y3+/Eu3+ co-doped TiO2 nano powder was prepared by sol-gel method and loaded on nickel foam by dropping method. Photocatalytic degradation performances of methyl orange under ultraviolet light and visible light were studied. The result indicates that La3+/Y3+/Eu3+ co-doped TiO2 is constituted by anatase phase which is single and stable, and its average grain size is 8 nm. The metallic ion doping changes the forbidden bandwidth of TiO2 nanoparticles. Its absorption coefficient is enhancement compared with pure TiO2 under visible light and the red shift phenomenon appears. The photocatalytic degradation of La3+/Y3+/Eu3+ co-doped TiO2 loading on nickel foam for methyl orange solution is 49% after 60 mins under visible light, which increases 345% compared with pure TiO2.

Ultra-desulfurization of sulfur recovery unit wastewater using thin film nanocomposite membrane

Herein, to meet the requirement of the stringent sulfur emission and discharge rate standards based on World Health Organization (WHO) and Environmental Protection Agency (EPA), polyamide/titanium dioxide (PA/TiO2) thin film nanocomposite (TFN) membranes were synthesized to remove sulfur compound from sulfur recovery unit (SRU) wastewater. The experiments were designed to appraise the effects of three independent factors including TiO2 nanoparticle concentration, transmembrane pressure (TMP), and operating temperature on membrane performance. Surface physiochemical and morphological properties of the resultant membranes were characterized with analytical techniques. The membrane characterizations revealed that the nanocomposite selective layer was formed on the surface of the substrate and its morphology and surface charge were affected by TiO2 loading. The performance test showed that TFN membrane was highly effective in sulfur removal as the minimum and maximum rejections with this type of membrane in the design space were 92.56% and 99.94%, respectively. In addition, the responses were predicted by the model equations designed via response surface methodology (RSM). Accordingly, the main effects and their interactions were statistically validated by the analysis of variance (ANOVA). In conclusion, the resulting TFN membranes demonstrated not only a very outstanding reduction in sulfur content (more than 97% below the aforementioned global surveillance standards’ level), but also overcame the trade-off effect between permeability and selectivity of the reference TFC membranes.

De-pollution efficacy of photocatalytic roofing granules

Photocatalytic building surfaces can harness sunlight to reduce urban air pollution. The NOx abatement capacity of TiO2-coated granules used in roofing products was evaluated for commercial product development. A laboratory test chamber and ancillary setup were built following conditions prescribed by ISO Standard 22197-1. It was validated by exposing reference P25-coated aluminum plates to a 3 L min−1 air flow enriched in 1 ppm NO under UVA irradiation (360 nm, 11.5 W m−2). We characterized prototype granule-surfaced asphalt shingles and loose granules prepared with different TiO2 loadings and post-treatment formulations. Tests performed at surface temperatures of 25 and 60 °C showed that NOx abatement was more effective at the higher temperature. Preliminary tests explored the use of 1 ppm NO2 and of 1 ppm and 0.3 ppm NO/NO2 mixtures. Specimens were aged in a laboratory accelerated weathering apparatus, and by exposure to the outdoor environment over periods that included dry and rainy seasons. Laboratory aging led to higher NO removal and NO2 formation rates, and the same catalyst activation was observed after field exposure with frequent precipitation. However, exposure during the dry season reduced the performance. This inactivation was mitigated by cleaning the surface of field-exposed specimens. Doubling the TiO2 loading led to a 50–150% increase in NO removal and NOx deposition rates. Application of different post-treatment coatings decreased NO removal rates (21–35%) and NOx deposition rates (26–74%) with respect to untreated granules. The mass balance of nitrogenated species was assessed by extracting granules after UV exposure in a 1 ppm NO-enriched atmosphere.

One-step in-situ preparation of N-doped TiO2@C derived from Ti3C2 MXene for enhanced visible-light driven photodegradation

As the most promising environment-friendly photocatalyst, titanium dioxide admittedly has two shortcomings of low sunlight utilization efficiency and poor quantum yield. Nitrogen doping and TiO2 loading on carbon materials can improve the above two problems, respectively. But a facile synthetic method for titanium dioxide composites with stable structure and high visible-light-driven photocatalytic activity is still desired by researchers. Herein we obtained two-dimensional layered nitrogen-doped carbon-supported titanium dioxides (N-TiO2@C) via a one-step in-situ fabrication way from a novel two-dimensional layered transition metal carbide Ti3C2 MXene as carbon skeleton and homologous titanium source. Based on the negatively charged and easily oxidized property of Ti3C2 MXene, it was assembled with nitrogen-containing cationic compound via electrostatic interactions and then in-situ transformed into nitrogen-doped carbon-supported TiO2 in a CO2 atmosphere at 550 °C. The obtained composites of porous 2D layered N-TiO2@C with high stability, outstanding electron transfer performance and excellent visible-light photocatalytic activity exhibits the high efficiency of phenol degradation with the apparent rate constant k of 1.646 × 10−2 min−1. It provides a facile new method for the preparation of visible-light-driven titanium dioxide with excellent catalytic performance, structural stability and good application prospects in the environmental purification.

Effect of TiO2 loading on the morphology and CO2/CH4 separation performance of PEBAX-based membranes

Membranes have attracted much attention as economical methods for industrial chemical processes. The effects of the titanium dioxide nanoparticle load on the morphology and CO2/CH4 separation performance of poly (ether-block-amide) (PEBAX-1657) mixed matrix membranes (MMMs) were investigated from pressures of 3–12 bar and temperatures of 30°C–60°C. The PEBAX membranes were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, thermal gravimetric analysis, atomic force microscopy and tensile strength analysis. The incorporation of TiO2 nanoparticles into the polymeric MMMs improved the CO2/CH4 gas separation performance (both the permeability and selectivity) of the membranes. The CO2 permeability and ideal CO2/CH4 selectivity values of the nanocomposite membrane loaded with 8 wt-% TiO2 were 172.32 Barrer and 24.79, respectively whereas those of the neat membrane were 129.87 Barrer and 21.39, respectively.

Solvent-controlled deposition of titania on silica spheres for the preparation of SiO2@TiO2 core@shell nanoparticles with enhanced photocatalytic activity

Controlled synthesis of SiO2@TiO2 core@shell particles is important for effectively exploiting the unique properties associated with core@shell architecture and obtaining photocatalysts with enhanced photoactivity. Herein, we propose an alternative, simple and rational solvent-based synthetic strategy for the reproducible and controlled coating of anatase nanocrystals (˜ 5 nm) over submicron SiO2 spheres. This strategy is based on the fact that titanium (IV) isopropoxide (TiP), the TiO2 precursor, exists in oligomeric (less reactive) and monomeric (more reactive) forms in ethanol-rich and isopropanol-rich solvent, respectively. The different reactivity of TiP in mixed solvents with varying ethanol/isopropanol ratio thus allows a precise control over the rate of titania deposition or TiO2 loading as well as the resultant particle morphology through simple manipulation of isopropanol/ethanol ratio of the solvent mixture used in the sol-gel process. Based on a detailed characterization of the samples using an array of complementary characterization techniques, a comprehensive discussion on the relationship between solvent composition, particle morphology and their photoactivity is presented. Photocatalytic dye degradation assays reveal that SiO2@TiO2 particles with uniform morphology obtained by solvent-controlled deposition show enhanced activity per mass unit of TiO2, thus confirming the importance of controlled deposition of titania for the design of efficient core@shell photocatalytic systems. The solvent-based synthetic strategy proposed here is facile, general and effective in controlling the structure and composition of the SiO2@TiO2 particles which, in turn, allows one to tune the photocatalytic properties and obtain core@TiO2 composite photocatalysts with improved photocatalytic activity.

Antifouling behaviour of PVDF/TiO2 composite membrane: a quantitative and qualitative assessment

The composite membranes of PVDF/TiO2 were prepared by a phase-inversion technique. Different amounts of TiO2 with respect to the weight of the polymer were incorporated in the casting solution to study qualitatively and quantitatively the antifouling property of the membrane. The membrane morphology was studied using a high-resolution scanning electron microscopy and atomic force microscopy, whereas the crystalline nature was studied using X-ray diffraction method. The interfacial interactions between foulants and TiO2 immobilized membranes were also evaluated using the extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) approach. The XDLVO theory revealed an increase in repulsive interactive energy barrier with an increase in TiO2 loading, thus causing to improve the antifouling property of the membrane. Intercalation of TiO2 nanoparticles efficiently improved the porosity and wettability of the polymeric membranes, which could be confirmed by the contact angle analyzer analysis. The modified PVDF membranes exhibited excellent antimicrobial properties against Gram-negative Escherichia coli as confirmed from the halo zone and activity test. The permeation experimental results also showed high protein rejection of bovine serum albumin and humic acid (foulant) for membranes with optimum TiO2 loading of 0.01 g/g of PVDF polymer. However, at a concentration of 0.02 g TiO2/g of PVDF a negative effect on the membrane property was observed due to the former non-uniform distribution.

Photocatalytic effects on the quality of pork packed in the package combined with TiO2 coated nonwoven fabrics

AbstractThe ability of titanium dioxide (TiO2) to generate reactive oxygen species (ROS) offers new opportunity to decontaminate perishable foods. The current study was aimed to prepare a TiO2 coated nonwoven fabric photocatalytic package (TiO2/NWF package) and assess the effects of in‐package photocatalysis on pork. In this study, layer by layer self‐assembly method was chosen to coat TiO2 nanoparticles on the NWF and eight layers TiO2 loading showed the higher photoactivity. A selected TiO2/NWF composite was combined with a package to form TiO2/NWF package. Pork was stored in the TiO2/NWF package, the antibacterial effects of TiO2 photocatalysis (TPC) on total viable count and Escherichia coli in pork were achieved. TPC treatment provided better antibacterial efficiency as compared with UV treatment alone. Moreover, TPC treatment significantly (p < .05) influenced pH and lipid oxidation after exposure for 45 min. These results indicate that TiO2/NWF package has the potential for preserving fresh foods.Practical applicationsTraditional thermal treatment can adversely affect the sensory and nutritional quality of foods, titanium dioxide (TiO2) photocatalysis as a nonthermal disinfection technology can provide a low cost and convenient approach to reduce the risk of microbial contamination and enhance the safety of fresh products. The current study developed a TiO2 coated nonwoven fabric photocatalytic package (TiO2/NWF package) and evaluated effects of in‐package photocatalysis on pork samples. Results showed that photocatalytic reactions took place in the TiO2/NWF package and the generated active ROS contributed to the inactivation of microbes. Therefore, TiO2 photocatalysis has great potential for ensuring food safety for the food industry.

Recyclable Xanthan/TiO2 Composite Cryogels towards the Photodegradation of Cr(VI) Ions and Methylene Blue Dye

Composite cryogels were prepared from xanthan gum (XG) precursor gels at 20 g L-1 containing TiO2 load at 5, 10, and 20 wt% and citric acid, as crosslinker. The effect of the pH over precursor gel on the properties of the resulting cryogels was evaluated. The characterization of the XG/TiO2 cryogels comprised compression tests, swelling degree (SD) determination, Fourier transform infrared vibrational spectroscopy in the attenuated total reflectance mode (FTIR-ATR), scanning electron microscopy (SEM), and X-ray microtomography (CT) analyses. The largest compressive modulus (E) was observed for XG/TiO2 10% cryogels prepared at pH 4.0, which amounted to 100±7 kPa, whereas the E value determined for bare XG cryogels was 29±3 kPa. XG/TiO2 10% cryogels presented larger pores and thicker walls than bare XG cryogels, as evidenced by SEM and CT analyses. FTIR-ATR spectra evidenced the ester bonds stemming from the esterification among carboxylic acid groups and/or XG hydroxyl groups. XG/TiO2 10% cryogels presented SD of (61±2) gwater/gcryogel, long-term stability in water, and outstanding photocatalytic properties in the presence of Cr(VI) ions and methylene blue (MB). The photocatalytic processes for the reduction of Cr(VI) to Cr(III) and for the photobleaching of MB fitted the first-order kinetic model, yielding rate constants of 0.019 varying min-1 and 0.0096 min-1, respectively. For both processes, the XG/TiO2 10% cryogels could be recycled five times without losing shape or efficiency.

Box-Behnken design to optimize the synthesis of new crosslinked chitosan-glyoxal/TiO2 nanocomposite: Methyl orange adsorption and mechanism studies.

A crosslinked chitosan-glyoxal/TiO2 nanocomposite (CCG/TNC) was synthesized by loading different ratios of TiO2 nanoparticles into polymeric matrix of crosslinked chitosan-glyoxal (CCG) to be a promising biosorbent for methyl orange (MO). Box-Behnken design (BBD) in response surface methodology (RSM) was applied to optimize various process parameters, viz., loading of TiO2 nanoparticles into CCG polymeric matrix (A: 0%-50%), adsorbent dose (B: 0.04-0.14 g/50 mL), solution pH (C: 4-10), and temperature (D: 30-50 °C). The highest MO removal efficiency of 75.9% was observed by simultaneous interactions between AB, AC, and BC. The optimum TiO2 loading, adsorbent dosage, solution pH, and temperature were (50% TiO2: 50% chitosan labeled as CCG/TNC-50), 0.09 g/50 mL, 4.0, and 40 °C. The adsorption of MO from aqueous solution by using CCG/TNC-50 in batch mode was evaluated. The kinetic results were well described by the pseudo-first order kinetic, and the equilibrium data were in agreement with Langmuir isotherm model with maximum adsorption capacity of 416.1 mg/g. The adsorption mechanism included electrostatic attractions, n-π stacking interactions, dipole-dipole hydrogen bonding interactions, and Yoshida H-bonding.

Enhanced photocatalytic decolorization of methyl orange dye and its mineralization pathway by immobilized TiO2/polyaniline

An immobilized TiO2/polyaniline (TiO2/PANI) bilayer photocatalyst was fabricated to decolorize methyl orange (MO) dye in aqueous solution. The synergistic decolorization of MO occurred via photocatalysis by TiO2 top layer and adsorption by PANI sub-layer. The fabrication of the photocatalyst was pertaining to the loading of TiO2 (0.32–2.24 mg cm−2) and PANI (0.32–1.92 mg cm−2). Increasing the loading would increase the thickness of the layer whereas an increment in the adsorption rate constant would essentially increase the synergistic photocatalytic–adsorption in the decolorization of MO. The TiO2 and PANI layer loading was optimized at 1.27 and 0.63 mg cm−2, respectively. The optimized TiO2/PANI photocatalyst removed MO dye by four and three times more effectively than the TiO2 and PANI single layer, respectively. The aeration, which supplied the dissolved oxygen, was optimized at 40 mL min−1 of flow rate. The photocatalytic degradation mechanism of MO was initiated by the demethylation followed by the aromatic ring opening and ended with a complete oxidation of the aliphatic chain to become CO2 and H2O. The TOC and IC analyses confirmed the mineralization of MO.

Novel Crayfish Shell Biochar Nanocomposites Loaded with Ag-TiO2 Nanoparticles Exhibit Robust Antibacterial Activity

A fast sol-dipping-gel method was applied to load Ag and TiO2 nanoparticles on the surface of crayfish shell biochar to make an inexpensive and novel nanocomposite. Tetra-n-butyl titanate (Ti(OC4H9)4) and silver nitrate (AgNO3) were used as the nanoparticle precursors. Crayfish shell was pyrolyzed to produce the biochar host. Paper-disk diffusion method was applied to measure antibacterial activities of the nanocomposites to E. coli. The maximum loading rate of TiO2 and Ag nanoparticles on the biochar reached 7.54% and 3.20%, respectively. Results of long-term antibacterial effect experiment showed that the Ag-TiO2-biochar had robust antibacterial activity and could be reused for multiple times. The inactivation of E. coli of initial concentration of 105 CFU/mL by Ag-TiO2-biochar under solar light reached around 99% of sterilization ratio in 5 min. In addition, the antibacterial ability of the nanocomposite was better in light than that in dark due to the presence of TiO2. Findings of this study suggest that the novel nanocomposite is a promising material for water treatment units and household water purifiers.

Effect of titanium dioxide on some mechanical, thermal, and surface properties of wood-plastic nanocomposites

The effects of TiO2 (titanium dioxide) loading were evaluated relative to mechanical, thermal, and surface properties of the wood-plastic nanocomposites (WPNs). Pine wood flour, mixed with maleic anhydride polypropylene (MAPP), TiO2 nanoparticles (0 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, and 5 wt%), and polypropylene, was compounded in a twin screw co-rotating extruder. The mass ratio of the wood flour to polypropylene (PP) was 50/50 (w/w) in all compounds. Test specimens were produced using injection molding machine from the pellets. Flexural and tensile properties, thermogravimetric analysis, surface roughness, wettability, and morphology of the manufactured nanocomposites were evaluated. Flexural and tensile properties of the wood-plastic nanocomposites increased with the increasing content of the TiO2. The surface roughness of the wood-plastic nanocomposites was reduced by increasing the content of TiO2. Increasing the loading of TiO2 increased the amount of residual ash and thermal stability.

Improved mechanical and antimicrobial properties of zein/chitosan films by adding highly dispersed nano-TiO2

Highly dispersible TiO2 nanoparticles were prepared through the hydrolysis of titanium alcohol, and a series of TiO2-modified zein/chitosan (CS) films were prepared through a process involving blending, solution casting and evaporation. The mechanical properties and the antibacterial capacity of the zein/CS/TiO2 films were characterized to explore the effects of different TiO2 nanoparticle contents. Results showed that the addition of nanoscale TiO2 remarkably improved the mechanical properties and thermal stability of the zein/CS/TiO2 film. The tensile strength of the zein/CS/TiO2 films significantly increased (p<0.05) with the increasing TiO2 loadings in films, reaching a maximum of 28.33 ± 1.53 MPa at 0.15 wt % TiO2 nanoparticles. The antibacterial effect of the composite films on Gram-positive bacteria (S. aureus) was more significant than that of Gram-negative bacteria (E. coli and S. enteritidis), and the antibacterial effect of UV light was better than that of dark conditions. In particular, the inhibition zones of zein/CS/TiO2 (0.15%) film against E. coli, S. enteritidis and S. aureus under UV light condition increased by 21.78%, 21.45%, and 26.44%, respectively, compared with the control. This study suggested that adding highly dispersible TiO2 nanoparticles is an effective method for improving the mechanical and antimicrobial properties of zein/CS films for various applications, such as medical and food packaging.

Thermal Properties and Non-Isothermal Crystallization Kinetics of Poly (δ-Valerolactone) and Poly (δ-Valerolactone)/Titanium Dioxide Nanocomposites

New poly (δ-valerolactone)/titanium dioxide (PDVL/TiO2) nanocomposites with different TiO2 nanoparticle loadings were prepared by the solvent-casting method and characterized by Fourier transform infra-red, differential scanning calorimetry, X-ray diffraction and scanning electron microscopy, and thermogravimetry analyses. The results obtained reveal good dispersion of TiO2 nanoparticles in the polymer matrix and non-formation of new crystalline structures indicating the stability of the crystallinity of TiO2 in the composite. A significant increase in the degree of crystallinity was observed with increasing TiO2 content. The non-isothermal crystallization kinetics of the PDVL/TiO2 system indicate that the crystallization process involves the simultaneous occurrence of two- and three-dimensional spherulitic growths. The thermal degradation analysis of this nanocomposite reveals a significant improvement in the thermal stability with increasing TiO2 loading.

UV-assisted surface modification of polyethersulfone (PES) membrane using TiO 2 nanoparticles

In this research commercial polyethersulfone (PES) membrane was modified using TiO2 nanoparticles (P-25 Degussa) and further irradiated using UV light to overcome the hydrophobicity and fouling nature of the membrane. Further the membranes were characterized using SEM and FTIR. Contact angle measurements study confirmed the hydrophilic tendency of the modified membrane by decreasing the contact angle from 73 degree to 20.28 degree. The modified membranes showed higher flux and better anti-fouling properties as compared to the unmodified counterparts. The optimum conditions were found to be 0.5 wt% TiO2 loading with 60 min membrane immersion and 10 min UV light illumination. The effect of different pH conditions of feed was analysed. Real wastewater filtration experiments also indicated better performance of modified membranes as opposed to neat PES membranes.