Commercial nano-TiO2 Research Articles

NOx degradation by cement mortar containing B-TiO2/MgAl-CLDH under visible light: Experimental and modeling

In this paper, an advanced photocatalyst, B-TiO2/MgAl-CLDH, was synthesized and applied in cement mortar. The photocatalytic NOx degradation ability of cement mortar containing B-TiO2/MgAl-CLDH under different initial NOx concentrations and flow rates was investigated. The results show that B-TiO2/MgAl-CLDH has stronger visible light absorption, lower recombination rate of electron-hole pairs and narrower optical band gap than commercial nano-TiO2 (P25), resulting in enhanced NOx removal efficiency. Specifically, the maximum NOx degradation ratio of B-TiO2/MgAl-CLDH is 23.4% within 30 min, which is about 5 times that of P25. For photocatalytic mortar, the initial NOx concentration (from 1.0 ppm to 2.0 ppm) and flow rate (from 1 L/min to 3 L/min) were positively correlated with NOx removal amount, while negatively correlated with NOx removal ratio. Based on the internal molecular diffusion properties of NOx, Langmuir-Hinshelwood and the power law kinetic models were used to predict the NOx degradation ability of photocatalytic mortar. The modeling of NOx degradation process presents a reliable prediction of the NOx removal ability of photocatalytic mortar, serving as a valuable tool for assessing the mortar’s NOx removal effectiveness for policymakers and engineers.

Pb(II) Uptake from Polluted Irrigation Water Using Anatase TiO2 Nanoadsorbent.

The adsorption characteristics of titanium dioxide nanoparticles (nano-TiO2) for the removal of Pb(II) from irrigation water were investigated in this work. To accomplish this, several adsorption factors, such as contact time and pH, were tested to assess adsorption efficiencies and mechanisms. Before and after the adsorption experiments, commercial nano-TiO2 was studied using X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM), energy dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The outcomes showed that anatase nano-TiO2 was remarkably efficient in cleaning Pb(II) from water, with a removal efficiency of more than 99% after only one hour of contact time at a pH of 6.5. Adsorption isotherms and kinetic adsorption data matched the Langmuir and Sips models quite well, showing that the adsorption process occurred at homogenous sites on the surface of nano-TiO2 by forming a Pb(II) adsorbate monolayer. The XRD and TEM analysis of nano-TiO2 following the adsorption procedure revealed a non-affected single phase (anatase) with crystallite sizes of 9.9 nm and particle sizes of 22.46 nm, respectively. According to the XPS data and analyzed adsorption data, Pb ions accumulated on the surface of nano-TiO2 through a three-step mechanism involving ion exchange and hydrogen bonding mechanisms. Overall, the findings indicate that nano-TiO2 has the potential to be used as an effective and long-lasting mesoporous adsorbent in the treatment and cleaning of Pb(II) from water bodies.

Synthesis of CuO x /TiO2 Photocatalysts with Enhanced Photocatalytic Performance.

CuO x /TiO2 co-photocatalysts with various Cu loading contents were synthesized by an impregnation method, and their photocatalytic activities were evaluated by photodegradation of organic pollutants under visible light illumination. The as-prepared CuO x /TiO2 composites exhibited a unique structure, in which CuO x clusters with about 2-3 nm nanocrystals were uniformly distributed on the TiO2 cube. The mesoporous Ti3+/TiO2 substrate with a uniform pore structure greatly improved the uniformity of the loaded Cu, wherein Ti3+ acted as a reducing agent for reducing Cu2+ to Cu+ and Cu0. The reversible process of the Cu species between Cu+ and Cu0 markedly enhanced the photocatalytic activity of the CuO x /TiO2 co-photocatalyst, by promoting the transfer of photogenerated electrons and suppressing the recombination of photogenerated electron and hole pairs. The synergistic effect between CuO x and TiO2 also played an important role in enhancing the photocatalytic activity of the CuO x /TiO2 co-photocatalyst. The results indicated that CuO x /TiO2-1 had the highest photocatalytic efficiency, which was 1.5 times higher than that of the commercial nano-TiO2 P25 under visible light, and demonstrated a good stability even after five recycles. This structural design and the valence control strategy for the Cu atom provide an idea that facilitates the utilization of visible light and the improvement of the photocatalytic activity of TiO2, promoting the practical application of the TiO2 photocatalyst.

Preparation of fly ash supporting nano-TiO2 composite photocatalyst by a wet mechanical grinding method

In this study, nano-TiO2 and FACs were used to prepare a composite photocatalyst (FACs-TiO2) by a wet mechanical grinding method. FACs-TiO2 was fabricated by using nano-TiO2 that was uniformly loaded on the surface of FACs, and the TiO2 particles were 20–30 nm in size. The degradation effect of FACs-TiO2 was comparable to that of commercial nano-TiO2 (P25). The reduction in TiO2 dosage in FACs-TiO2 could markedly reduce TiO2 application costs; thus, it shows promise for practical application.

Selenate Se(VI) reduction to elemental selenium on heterojunctioned rutile/brookite nano-photocatalysts with enhanced charge utilization

Newly synthesized nanocrystalline TiO2 mixed-phase photocatalysts are shown to surpass in Selenium (VI) reduction effectiveness the commercial P25 nanoTiO2 photocatalyst Heterojunctioned rutile (63 %)/brookite (37 %) (designated as R/b) nanoTiO2 is found to be the most effective photocatalyst achieving 95 % photo-assisted reductive deposition vs. 25 % only by the benchmark P25 composed of anatase (80 %) and rutile (A/r). This is attained at very high photocharge utilization with at least 5-fold less formic acid as hole scavenger. The superior performance of R/b is attributed to a favorable band alignment at the heterojunction and its 1D-dominated nanocrystal orientation enabling efficient co-adsorption and enhanced charge separation. The deposition of elemental Se further “auto-catalyzes” the photocatalytic process by enabling visible light activity with simultaneous suppression of charge recombination. In-depth probing of the R/b photocatalyst after selenium removal provides evidence of a 2-step mechanism involving (a) reductive adsorption of Se(VI)aq → Se(IV)surf with the participation of co-adsorbed formate and Ti3+ defects, and photoreduction of Se(IV)surf → Se(0)surf.

Transport of nanoparticulate TiO2 UV-filters through a saturated sand column at environmentally relevant concentrations

The fate of sunscreen residues released during bathing activities around recreational areas is an emerging concern regarding the potential ecotoxicity of some of their ingredients, including nanoparticulate TiO2 UV-filters. To assess the extent of contamination in the natural medium, sand-packed column experiments were carried out with bare TiO2 engineered nanoparticles (ENPs) and two commercial nano-TiO2 UV-filters coated with either SiO2 (hydrophilic) or a combination of Al2O3 and simethicone (amphiphilic). The high sensitivity of (single particle)ICPMS online monitoring of the breakthrough curves made it possible to inject the ENPs at trace levels (2–100 μg L−1) in eluents composed of 10−3 and 10−2 M NaCl and pHs of 5.7 and 7.8. The deposition of all ENPs in the sand increased with the ionic strength and decreased with the pH of the carrier. Both bare and SiO2-coated ENPs showed a clear control by the electrostatic interactions between the particles and the quartz grains surfaces, in partial agreement with classical DLVO theory. Unexpectedly high rates of transfer were observed with the amphiphilic UV-filter, which could be explained by the addition of a contribution to the DLVO model to account for the steric repulsion between the sand collector and the polysiloxane surface layer of this ENP. These results demonstrate the major role played by the coating of UV-filters regarding their fate in porous media like soils, sediments and aquifers.

Visible-Ultraviolet Upconversion Carbon Quantum Dots for Enhancement of the Photocatalytic Activity of Titanium Dioxide.

Visible–ultraviolet upconversion carbon quantum dots (CQDs) are synthesized with a hydrothermal method using l-glutamic acid (l-Glu) and m-phenylenediamine (MPD) and then combined with commercial nano-TiO2 to prepare CQDs/TiO2 composites. The fluorescence spectra prove that the prepared CQDs can convert approximately 600 nm visible light into 350 nm ultraviolet light. In photocatalysis experiments, CT-1, a CQDs/TiO2 composite with 1:1 molar ratio of l-Glu to TiO2, has the best degradation efficiency for methyl orange (MO). Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) experiments confirm that CT-1 is composed of quasi-spherical nano-TiO2 and CQDs with a crystal plane of graphitic carbon. CT-1 can degrade 70.56% of MO (40 ppm) within 6 h under the irradiation of a 600 nm light source, which is close to its degradation rate of 78.75% under 365 nm ultraviolet light. The apparent rate constant of CT-1 degradation equation is 12.7 times that of TiO2. Free radical scavenging experiments and electron spin resonance (ESR) tests show that the degradation ability should be attributed to the existence of h+ and •OH under visible light. Therefore, we provide a simple and low-cost solution with heavy-metal-free products to improve the photocatalytic performance of TiO2.

Self-cleaning and air purification performance of Portland cement paste with low dosages of nanodispersed TiO2 coatings

The strong agglomeration potential and poor re-dispersibility of nano TiO2 particles in powder form seriously affect the depollution and self-cleaning performances. The nano TiO2 particles in hydrosol form can be stably dispersed in aqueous solution, but the synthetic temperature influences the crystal pattern, stability, and hydrodynamic diameter of nano TiO2 particles. In this study, a stable and nano dispersed anatase TiO2 hydrosol is synthesized by hydrolysis of titanium isopropoxide, and the effects of synthetic temperature on physicochemical properties and stability of TiO2 hydrosol are discussed. The photocatalytic and self-cleaning performances of synthetic TiO2 hydrosol coating are characterized by the colour change rate of Rhodamine B and NOx conversion UV irradiation. Compared with a commercial nano TiO2 powder (Degussa P-25), the TiO2 hydrosol coating with very low dosages shows better photocatalytic and self-cleaning performances under the same experimental conditions.

Sustainable development of inexpensive visible-range CuO[sbnd]TiO2 nano-photocatalysts deploying in situ recovered glass fiber and Cu(CH3COO)2 from waste printed wiring board: Optimal lignin photo-degradation for valuable products

Inexpensive glass fiber (GF) support as well as copper acetate precursor recovered in situ from waste printed wiring boards (WPWB) have been utilized for preparation of GF supported CuO-TiO2nano-photocatalyst (NP) through sequential sol-gel and wet-impregnation methodology deploying solar-resembling quartz-halogen radiation (SRQHR) (wavelength: 0.32–1.1 μm).The optimal NP (QGF-CuO-TiO27.5) possessed finer nano TiO2 and CuO crystalline phases (7.31 nm) and higher BET surface area (62.107 m2.g−1) compared to conventionally prepared NP (crystallite size: 33.38 nm, surface area: 42.170 m2.g−1); thus, advocating the supremacy of SRQHR over conventional thermal-energy. Furthermore, UV–Vis-NIR diffuse spectroscopy revealed that QGF-CuO-TiO27.5 was capable of absorbing light in the visible spectrum, owing to its low bandgap energy (2.26 eV). Taguchi orthogonal design was used to investigate and optimize the efficacy of the prepared NPs in lignin (rice straw extracted) photo-degradation process employing an energy-efficient SRQHR assisted rotating batch reactor (RBR). The optimal QGF-CuO-TiO27.5 rendered a significantly higher lignin photo-degradation (89.73%) compared to the conventionally prepared NP (54.53%) at optimal conditions (70 °C; 50 min; 200 rpm). Moreover, lignin photo-degradation in RBR exhibited higher degradation percentage (89.73%) compared to that (67.78%) achieved in a conventionally agitated reactor. Overall sustainability of lignin photo-degradation process for production of lignin-derivatives (vanillin, syringaldehyde, vanillic acid) analysed via life cycle assessment (LCA) study evidently revealed that the QGF-CuO-TiO27.5 catalysed process resulted less environmental impacts in comparison with its conventional counterpart and commercial nano-TiO2 catalyst.

Evaluation of nano-TiO2 on properties of cementitious mortars

This work deals with the effect in fresh and hardened properties of nano-TiO2 as addition in cement-based mortars. Three commercial nano-TiO2 powders were characterized by laser granulometry, XRD, FRX, zeta potential, BET and SEM. Two cementitious mortars were produced with nano-TiO2, an industrialized and a non-industrialized type; then, these mortars were characterized by flowability, surface roughness, flexural strength and surface fracture. The results showed that the nano-TiO2 addition reduced the flowability in terms of spread on table of the mortars. For surface roughness, in the industrialized mortars, the nanoparticles resulted in a smoother surface, while in the non-industrialized mortars, the nanoparticles formed a rougher surface. For flexural strength, in the non-industrialized mortars, the higher the nanoparticles amount, the higher the strength, while in the industrialized mortars no tendency was verified. In addition, from SEM analysis, it was noted that the fracture of the samples presented a tortuous aspect and growth through the region between cement paste and aggregates. Keywords: nano-TiO2; cementitious mortar, flowability; flexural strength

A sustainable and cost effective surface functionalization of cotton fabric using TiO2 hydrosol produced in a pilot scale: Condition optimization, sunlight-driven photocatalytic activity and practical applications

This paper aimed to develop a successful multi-functional finishing of cotton fabric with TiO2 hydrosol produced on a pilot-scale as a sustainable and cost-effective alternative to the market dominating nano TiO2 powders. The surface morphology, crystalline phase and photocatalytic activity of the finished fabric was evaluated and compared with those finished with two commercial nano TiO2 powders. The finished fabric was tested for its ability to decompose indoor formaldehyde and to self-clean three different stains under illumination. The results indicated that 130 °C is the optimal curing temperature to obtain the finished fabric with higher TiO2 loading and catalytic activity. Increasing the pH of the TiO2 hydrosol enhanced the TiO2 loading, however, led to a lower activity. The catalytic activity of the TiO2 hydrosol finished fabric was similar to or higher than that of finished fabric with nano TiO2 powders. The catalytic activity of the hydrosol finished fabric was found to be sunlight-driven and greatly dependent on weather conditions. This finished fabric shows excellent decomposition of indoor formaldehyde and self-cleaning performance on different stains under compact fluorescent or solar irradiation.

Crystallization of microporous TiO2 through photochemical deposition of Pt for photocatalytic degradation of volatile organic compounds.

The photocatalytic mineralization efficiency of volatile organic compounds (VOCs) is determined by adsorption of reactants, separation of charge carriers, and reaction activity of catalyst surface. Herein, we provide a strategy to synthesize a novel catalyst, namely, PhPt-Micro, which is characterized by high adsorption ability, charge separation efficiency, and surface reaction activity. Toluene was chosen as the model VOC. The effects of photochemical deposition of Pt on the physical properties of microporous amorphous TiO2 (Micro) and toluene mineralization were studied using N2 adsorption/desorption, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, GC-flame ionization detection, and surface photovoltage spectroscopy (SPS) analyses. After photochemical treatment, the structure of Micro was optimized, and Pt nanoparticles were successfully deposited at the outlet of electrons on the catalyst surface. SPS result proved that the optimized structure enhanced the separation efficiency of charge carriers and the migration of photo-generated electrons to the PhPt-Micro surface. The quasi-equilibrium adsorption amount of toluene over PhPt-Micro was two times higher than that with commercial nano TiO2 (P25). The micropores concentrated toluene on the catalyst surface and hindered intermediate desorption. The mineralization efficiency of toluene over PhPt-Micro was 2.4 and 5.9 times higher than those over Micro and P25, respectively.

The decolourisation of Methyl Orange and textile effluent under UV using commercial and synthesized nano-TiO2

The efficiency of the nanophotocatalysts was determined in a laboratory prepared solutions of model dye compound methyl orange (MO), which is a dyestuff typically applied on textiles. The reduction in the concentration of the dye over time was measured by using UV-VIS spectrophotometry. The decolourisation of MO solutions was characterized at the onset and after exposure to 9W germicidal UV lamps at various time intervals, viz. 30, 60, 120, 180, 300 and 420 minutes. The color transformation from dark-orange, (MO) to a transparent clear solution or a slightly colored solution is an indication of the decomposition of the organic dye contaminants into lower molecular weight organics and innocuous CO2 and water. The results show that the commercial nano-TiO2 is more efficient in decolourising the model dye and the textile effluents.

Removal of Waterborne Pathogen by Nanomaterial-Membrane Coupling System.

The waterborne pathogenic viruses threaten human health. And the nanomaterial-membrane coupling system is promising in virus removal. In this study, phage MS2 was selected as the model virus to investigate the removal of virus with the coupling system. Results revealed that commercial nano TiO2 (Degussa Aeroxide P25) showed both of excellent adsorption and photocatalysis performance for virus removal compared with nano ZnO, nano Fe3O4, carbon nanotube, graphene, nano Ni and Nano TiO2 (anatase). In P25 photocatalysis process, the removal efficiency of phage MS2 increased with the increase of P25 concentration (0~1000 mg L-1), virus initial concentration (102~106 PFU mL-1), UV irradiation doses (5~120 mJ cm-2) and UV light intensity (0.126~0.742 mW cm-2). However, when the P25 concentration increased to over 1000 mg L-1, the virus removal efficiency would remain stable with the increase of P25 concentration. The nanomaterial-membrane coupling system showed excellent performance for virus removal, which was mainly attributed to the adsorption and photocatalysis of P25, and the intercept of membrane. When the P25 concentration was 100 mg L-1, UV irradiation dose was 20 mJ cm-2 and transmembrane pressure was 20 kPa, the phage MS2 removal efficiency could be up to 100%.

Size-Dependent Level Alignment between Rutile and Anatase TiO2 Nanoparticles: Implications for Photocatalysis.

Motivated by the enormous importance of nanoscale TiO2 in a wide range of photocatalytic applications and the ill-understood high activity of the commercial nano-TiO2 photocatalysts, we provide a predictive map of how the anatase-rutile level alignment varies from the smallest nanoparticles (NPs) to the bulk. Specifically, we compute the size dependence of the energies of vacuum-referenced electronic levels in a range of realistically structured rutile and anatase TiO2 NPs employing accurate all-electron density functional calculations. In agreement with most recent work, a staggered type II anatase level alignment is predicted for the bulk phases, which we further find to persist into the regime of large NPs. We predict that other level alignments will emerge when the diameter of the TiO2 NPs is reduced below ∼15 nm. Our results suggest how experiment could test the widely debated importance of the bulk-like type II anatase level alignment for enhanced photoactivity of nano-TiO2.

Microwave Treated Bentonite Clay Based TiO2 Composites: An Efficient Photocatalyst for Rapid Degradation of Methylene Blue.

The composites of TiO₂ and bentonite were synthesized under microwave conditions. Formation of anatase TiO₂ nanoparticles was achieved within 10 minutes by microwave treatment at 180 °C on the clay surface. Phase composition, particle morphology, specific surface area, chemical bonding etc. of these samples were characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), nitrogen gas adsorption method (BET) and fourier transform infrared spectroscopy (FTIR). The photo catalytic activity of the as prepared material to degrade methylene blue resulting in complete photomineralization to CO₂ and H₂O was monitored by UV-Vis spectroscopy and gas chromatography. The effect of TiO2 content on the photocatalytic activity was also investigated. Bentonite containing 50% TiO₂ by weight showed the highest photocatalytic activity because of its relatively large specific surface area and pore volume. Overall our findings show that the photocatalytic activity of resulting composite is more efficient than commercial nano-TiO₂ and thus could therefore be an economic competitive candidate for contaminated water remediation.

Application of sonochemical technique for sustainable surface modification of polyester fibers resulting in durable nano-sonofinishing

In this study firstly we aimed at introducing the effects of ultrasound and sonochemistry in surface modification of polyester fibers. For this purpose, surface modification of polyester fibers was achieved by ultrasound, and contact angle and water spreading time measurements were used to confirm the treatment efficiency. Hydroxylation of terephthalate was occurred by hydroxyl radicals formed during water sonolysis, forming functional groups on polyester surface, as confirmed by XPS analysis, improving the wettability. Creation of hydroxyl groups under sono surface modification was further assessed by dyeing the samples with reactive dye. Secondly, we investigated the durable nano-sono-finishing of polyester fibers by nano TiO2 particles under ultrasonic bath. Washing durability of the sono-synthesized TiO2 nanoparticles was evaluated confirming the effective role of sonochemical technique in polyester surface modification. Thirdly, the self-cleaning activity of sono-synthesized nano TiO2 treated samples toward degradation of Methylene Blue stain was superior to coating of fabric with commercial nano TiO2 using identical procedure.

Effect of Au content on the enhanced photocatalytic efficiency of mesoporous Au/TiO2 nanocomposites in UV and sunlight

Detoxification of harmful dyes through nonconventional catalytic processes is getting thrust in light of environmental remediation. Current work reveals synthesis of gold–titania (Au/TiO2) mesoporous nanostructure and its enhanced photocatalytic performance for degradation of alizarin dye. Optically, Au/TiO2 shows a characteristic surface plasmonic absorption band at 520 nm, whereas X-ray diffraction (XRD) pattern reveals the anatase phase of TiO2 with fcc unit cell structure and tetragonal geometry. X-ray photon spectroscopy depicts (Au 4f 7/2 at 84.0 and Au 4f 5/2 at 87.7 eV) the elemental state of gold (Au0). Specific surface area was witnessed to decrease with increase of Au content (169, 141, 130, and 119 m2/g for 1, 2, 3, and 4 wt%, respectively). The mesoporous Au/TiO2 nanocomposite showed higher catalytic performance in comparison to commercial nano-TiO2 (P25), which is credited to better charge delocalization at metal semiconductor interface. The reusability studies of the photocatalyst exhibited more than 98% degradation of the dye even after 10 consecutive cycles.

TiO2 preparation by improved homogeneous precipitation and application in SCR catalyst

Ultrasonic treatment and hydrothermal method were applied in the traditional homogeneous precipitation for nano-TiO2 preparation, which was used as carrier material for the production of honeycomb selective catalytic reduction (SCR) catalyst. The influence rules of the two improved methods on characterization of TiO2 samples, denitration activity and mechanical strength of honeycomb SCR catalyst samples were mainly focused on. The results indicate that the specific surface area, particle size and uniformity of TiO2 samples are significantly improved by both of the ultrasonic and hydrothermal treatments compared with the traditional homogeneous precipitation. Also, the denitration activities of catalyst samples are enhanced by the two improved methods (the NOx reduction ratio increases from 88.89% to 95.45% by ultrasonic homogeneous precipitation process, and to 94.12% by hydrothermal homogeneous precipitation process). On the other hand, because of good spherical shape and high particle distribution of TiO2 sample from hydrothermal homogeneous precipitation process, the corresponding honeycomb catalyst samples get the best mechanical strength, which is even higher than that of the reference sample from commercial nano-TiO2. So, it is concluded that the hydrothermal homogeneous precipitation can be a feasible and effective preparation method of TiO2 carrier for the honeycomb SCR catalyst production.

Effect of silica/titania ratio on enhanced photooxidation of industrial hazardous materials by microwave treated mesoporous SBA-15/TiO2 nanocomposites

In this study microwave assisted technique has been adopted for the synthesis of different weight ratios of TiO2 dispersed on Santa barbara amorphous-15 (SBA-15) support. Morphological study revealed TiO2 particles (4–10 nm) uniformly distributed on SBA-15 while increases in SBA-15 content results in higher specific surface area (524–237 m2/g). The diffraction intensity of 101 plane of anatase polymorph was seen increasing with increase in TiO2 ratio. All the photocatalysts were having a mesoporous nature and follow the Langmuir IV isotherm, SBA-15 posses the highest pore volume (0.93 cm3 g−1) which consistently decreased with TiO2 content and was lowest (0.50 cm3 g−1) in case of 5 wt% of TiO2 followed by P25 (0.45 cm3 g−1) while pore diameter increased after TiO2 incorporation due to pore strain. The photocatalytic activity of the nanocomposites were analysed for the photodegradation of alizarin dye and pentachlorophenol under UV light irradiation. The reaction kinetics suggested the highest efficiency (98 % for alizarin and 94 % for PCP) of 5 wt% TiO2 compared to other photocatalysts, these nanocomposites were reused for several cycles, which is most important for heterogeneous photocatalytic degradation reaction. This study demonstrates the synthesis of silica embedded TiO2 nanocomposites by microwave assisted technique and their catalytic influence on degradation of organic dyes and pollutants. Higher loading of titania (SBA-15/TiO2, 1:5) results better catalytic performance than commercial nano TiO2 (P25).