P25 Titania Research Articles

In situ synthesis of the mesoporous C–TiO2 microspheres derived from partial hydrolysis tetrabutyl titanate for enhanced photocatalytic degradation under visible light

C–TiO2 microspheres were prepared in situ through microwave-assisted solvothermal method followed by low-temperature heat treatment in this study. Different carbon content doping samples were obtained through different temperatures of heat treatment. The characterization results indicate that C–TiO2 samples are exclusively composed of anatase crystallites, and also the interstitial carbon and the surface carbonate species are confirmed existed in the samples, which could significantly enhance the photocatalytic activity under visible light. When irradiated for 60 min under 5 W visible-light, the degradation efficiency of 40 mg/l methylene blue (200 mg catalyst) and 10 mg/l methyl orange (100 mg catalyst) can reach 92.59% and 98.42%, respectively, which is significantly higher than that of commercial titania P25 (5.74% and 24.53%, respectively). In addition, the sample exhibits excellent recyclability and stability, which might be considered as a novel and facil scheme for modification of titania photodegradation driven by visible light.

Optimization of Photo-Fenton Catalyst Preparation Based Bamboo Carbon Fiber by Response Surface Methodology

In this paper, the residue from bamboo factory has been used to design photo-Fenton catalyst, which has the advantages of low cost and magnetic recycling. The photo-Fenton catalytic performance of the biocarbon-based catalyst was excellent and its optimal preparation process was also explored by response surface methodology. First, bamboo-carbon fiber was selected as the photo-Fenton catalyst carrier. Subsequently, the surface of the carbon fiber was modified, with which dopamine, nano-Fe3O4 and nano-TiO2 were successively loaded by hydrothermal method. After examined single factor tests, four factors including dopamine concentration, ferric chloride mass, P25 titanium dioxide mass and liquid-solid ratio were selected to the characteristic values. The degradation efficiency of photo-Fenton catalyst to methylene blue (MB) solution was treated as the response value. After the analysis of the response surface optimization, it was showed that the significance sequence of the selected 4 factors in terms of the MB degradation efficiency was arranged as following: dopamine concentration > liquid-solid ratio > P25 titanium dioxide quality > ferric chloride quality. The optimal process parameters of fiber-carbon catalyst were affirmed as following: the 1.7 mg/mL concentration of dopamine, the 1.2 g mass of ferric chloride, the 0.2 g mass of P25 titanium dioxide and the liquid-solid ratio of 170 mL/g. The experiment-measured average MB degradation efficiency performed by the optimized catalyst was 99.3%, which was nearly similar to the model-predicted value of 98.9%. It showed that the prediction model and response surface model were accurate and reliable. The results from response surface optimization could provide a good reference to design bamboo-based Fenton-like catalyst with excellent catalytic performance.

Tuning the morphology, stability and optical properties of CsSnBr3 nanocrystals through bismuth doping for visible-light-driven applications.

In this investigation, we have demonstrated the synthesis of lead-free CsSnBr3 (CSB) and 5 mol% bismuth (Bi) doped CSB (CSB'B) nanocrystals, with a stable cubic perovskite structure following a facile hot injection technique. The Bi substitution in CSB was found to play a vital role in reducing the size of the nanocrystals significantly, from 316 ± 93 to 87 ± 22 nm. Additionally, Bi doping has inhibited the oxidation of Sn2+ of CSB perovskite. A reduction in the optical band gap from 1.89 to 1.73 eV was observed for CSB'B and the PL intensity was quenched due to the introduction of the Bi3+ dopant. To demonstrate one of the visible-light-driven applications of the nanocrystals, photodegradation experiments were carried out as a test case. Interestingly, under UV-vis irradiation, the degradation efficiency of CSB'B was roughly one order lower than that of P25 titania nanoparticles; however, it was almost five times higher when driven by visible light under identical conditions. The water stability of CSB'B perovskite and suppression of the oxidative degradation of Sn were confirmed through XRD and XPS analyses after photocatalysis. Moreover, by employing experimental parameters, DFT-based first-principles calculations were performed, which demonstrated an excellent qualitative agreement between experimental and theoretical outcomes. The as-synthesized Bi-doped CSB might be a stable halide perovskite with potential in visible-light-driven applications.

Evaluation of Antifungal Properties of Titania P25.

Commercial titania photocatalyst—P25 was chosen for an antifungal property examination due to it exhibiting one of the highest photocatalytic activities among titania photocatalysts. Titania P25 was homogenized first (HomoP25) and then annealed at different temperatures. Additionally, HomoP25 was modified with 0.5 wt% or 2.0 wt% of platinum by a photodeposition method. The obtained samples were characterized by diffuse-reflectance spectroscopy (DRS), X-ray photoabsorption spectroscopy (XPS), X-ray diffraction (XRD) and Raman spectroscopy. Moreover, photocatalytic activity was tested for methanol dehydrogenation under UV/vis irradiation. The spore-destroying effect of photocatalysts was investigated against two mold fungal species, i.e., Aspergillus fumigatus and Aspergillus niger. Both the mycelium growth and API ZYM (estimation of enzymatic activity) tests were applied for the assessment of antifungal effect. It was found that annealing caused a change of surface properties of the titania samples, i.e., an increase in the noncrystalline part, a growth of particles and enhanced oxygen adsorption on its surface, which resulted in an increase in both the hydrogen evolution rate and the antifungal effect. Titania samples annealed at 300−500 °C were highly active during 60-min UV/vis irradiation, inhibiting the germination of both fungal spores, whereas titania modification with platinum (0.5 and 2.0 wt%) had negligible effect, despite being highly active for hydrogen evolution. The control experiments revealed the lack of titania activity in the dark, as well as high resistance of fungi for applied UV/vis irradiation in the absence of photocatalysts. Moreover, the complete inhibition of 19 hydrolases, secreted by both tested fungi, was noted under UV/vis irradiation on the annealed P25 sample. It is proposed that titania photocatalysts of large particle sizes (>150 nm) and enriched surface with oxygen might efficiently destroy fungal structures under mild irradiation conditions and, thus, be highly promising as covering materials for daily products.

Alkaline hydrothermal treatment of P25 titanium dioxide for low temperature sintering of Li2TiO3 tritium breeding ceramics

• The structural properties of Ti sources affect the sintering activity of Li 2 TiO 3 . • P25-AHT is superior to anatase TiO 2 in reducing sintering temperatures of Li 2 TiO 3 . • The prepared Li 2 TiO 3 ceramics have high crushing load and thermal conductivity. For solid tritium breeding materials, a high sintering temperature is essential to achieve satisfactory density, high crushing load, favorable physical and chemical properties, while lithium volatilization and grain coarsening occur at higher sintering temperature, which are not conducive to tritium production and release. Therefore, low temperature sintering of lithium containing ceramics needs to be studied. In this work, P25 titanium dioxide was hydrothermally treated in alkaline solution, and then used as titanium source to prepare Li 2 TiO 3 ceramics. The prepared Li 2 TiO 3 ceramics exhibit uniform and dense microstructure and extremely high crushing load (a.v. 78.93 ∼ 83.98 N) at a relative low sintering temperature (750 ∼ 800 °C). The thermal conductivity of Li 2 TiO 3 ceramic sintered at 800 °C is calculated to be 3.48 W/m•K at room temperature, retaining 2.50 W/m•K at 773 K, which is comparable to the values in literatures. The results suggest the sintering activity of Li 2 TiO 3 is greatly enhanced when alkaline hydrothermally treated P25 is used as titanium source.

Microwave-assisted synthesis of Ag-Cu co-modified TiO2 catalyst for efficient photocatalytic oxidation of M-cresol

In this study, the photocatalytic oxidation of toxic industrial compound m-cresol by Ag-Cu/-TiO2 P25 catalyst under UV light irradiation has been studied. Photocatalysts of P25 titanium dioxide modified with copper and silver are prepared by a new cost-effective microwave-assisted method. By varying the molar ratio Cu:Ag (1:1, 1:2, 2:1), X-ray diffraction analysis manifested a change in anatase/rutile amounts ratio and the appearance new phases Ag2O and Cu3Ti besides metallic Ag. The photocatalytic activity has been examined as a function of catalyst dose, the initial concentration of m-cresol, and the addition of airflow. The highest photocatalytic degradation performance is achieved for 2 g/L of 1:1 Ag/Cu-TiO2 P25 catalyst and 50 mg/L m-cresol in air, much better than TiO2 P25 catalyst, with good stability and reused after recovery. The improved catalyst gives any industries that use m-cresol as an element in fabricating other products the possibility of controlling the rejected concentrations of MC in wastewater and minimizing its harmful impact on the environment.

Antimicrobial properties of pristine and Pt-modified titania P25 in rotating magnetic field conditions

Effective and cheap water purification is one of the most important tasks facing humanity. Among various methods of water treatment, heterogeneous photocatalysis is probably most recommended. However, the application of artificial sources of irradiation results in high investment and operating costs. Accordingly, either vis-responsive photocatalysts or different ways of photocatalyst activation should be developed. In the present study, rotating magnetic field (RMF) has been tested to inactivate gram-positive (Staphylococcus epidermidis) and gram-negative (Escherichia coli) bacteria in the presence of pristine and Pt-modified titania P25 photocatalyst. Liquid cultures of the bacteria have been exposed to the titania and RMF (RMF frequency of 1–50 Hz, RMF magnetic induction of ca. 19.92 mT, 180 min exposure time, temperature of incubation at 37 °C). It has been found that highly active titania photocatalyst might also work in the absence of photoirradiation but under RMF. Moreover, its modification with platinum besides highly improved photocatalytic activity (tested for two model reactions of oxidative decomposition of acetic acid and anaerobic dehydrogenation of methanol under UV/vis irradiation) results in significant enhancement of antimicrobial effect under RMF. Additionally, photocatalysts with larger content of oxidized forms of platinum show higher antimicrobial activity, and thus it is proposed that platinum oxides are more active than zero-valent platinum under RMF. This study provides evidence of antimicrobial effect of titania without photoirradiation, indicating that RMF might efficiently activate photocatalyst.

In silico ecotoxicity assessment of photoinduced imidacloprid degradation using HPLC–HRMS, QSAR and ecotoxicity equivalents

BackgroundImidacloprid is among the most widely used insecticides and today is found in surface and ground water worldwide. It has been registered in the EU watchlist for monitoring. To prevent imidacloprid from entering water bodies, advanced oxidation processes (AOP) have been intensely researched. Photo-irradiation proved one of the most efficient methods to degrade and eliminate anthropogenic micropollutants from waters. The ecotoxicity assessment of photoinduced degradation and transformation products especially in the absence of reference standards is still heavily explored.ResultsIn this study, UVA and UVC irradiation in combination with titanium dioxide P25 as photocatalyst were investigated for their degrading and eliminating effects and effectiveness on imidacloprid. Humic acid was used as natural organic matter additive. High-performance liquid chromatography coupled with high-resolution mass spectrometry allowed to identify and monitor imidacloprid and its degradation intermediates yielding seven new structures and concentration–time (c–t) profiles. The correlation of structures and the application of radical scavengers and photocatalyst helped distinguish between direct photoinduced and indirect hydroxyl radical-induced degradation mechanisms. The identification of hydroxylated products and intermediates indicated the indirect degradation pathway, which could be suppressed by addition of a radical scavenger. The absence of hydroxylated intermediates and fragments pointed towards the direct absorption-induced degradation. Two degradations products were traced back to the direct mechanism, whereas all other products followed the indirect mechanism. The ecotoxicity of the identified compounds was assessed by quantitative structure–activity relationship (QSAR) analysis. Most products were predicted as less ecotoxic. Ecotoxicity equivalents (ETEs) were introduced allowing a classified ranking of the products and an assessment of the overall hazardous potential of the irradiated solution at a given moment. Generally, the number of hydroxyl substituents was inversely correlated to ecotoxicity. From the c-t curves, time-dependent ETE profiles were established.ConclusionsStructure elucidation and c-t profiles from liquid chromatography–high-resolution mass spectrometry allowed to distinguish between direct and indirect degradation mechanisms. Structure specific ecotoxicity assessment could be achieved through QSAR analysis. Ecotoxicity hazard was ranked based on ETEs. The time-dependent ETE profile proved suitable to reflect the effect of irradiation duration and allow to estimate the irradiation time required to eliminate ecotoxicity, which may be relevant for potential applications in wastewater treatment plants.

A Light(er) Approach for the Selective Hydrogenation of 5-Hydroxymethylfurfural to 2,5-Bis(hydroxymethyl)furan without External H2.

The selective conversion of 5-hydroxymethyfurfural (HMF), a biomass-derived platform molecule, to value added chemicals can ease the burden on petroleum-based fine chemical synthesis. The active contribution of renewable energy sources along with low cost, environmental friendliness, and a simple reaction system must be adopted for better sustainability. In this context, photocatalytic selective hydrogenation of HMF to 2,5-bis(hydroxymethyl)furan (BHMF) was achieved over P25 titania nanoparticles without chemical squander. Simultaneously the photo-oxidation of p-methoxybenzyl alcohol (MeOBA) to p-methoxybenzaldehyde (MeOBaL), similar to biomass-derived vanillin, was carried out, abolishing the need of additional redox reagents. This system put forward the competent employment of photogenerated excitons for the valorization of lignocellulosic biomass to fine chemicals, which is an urgent requirement for sustainable chemical synthesis.

Experimental and theoretical insight into DSSCs mechanism influenced by different doping metal ions

Mesoporous TiO2 doped with Cu2+, Mn2+, and Ni2+ ions nanomaterials with 0.4% content of dopant ions were synthesized via the optimized sol-gel method. Experimental results were compared with an extensive theoretical study of doped-TiO2 nanoparticles using density functional theory extended by Hubbard correction. Structural analyses performed indicate anatase structure (with minor impurity of brookite) of spherical-shaped nanoparticles with a size below 15 nm. Further, XPS and EPR analyses confirmed the doping of metal ions into TiO2 and the formation of oxygen vacancies. The characteristic narrowing of the energy bandgap was observed with a higher concentration of dopants than 0.4%. Nanomaterials were used to fabricate solar cells sensitized with N3 dye. Comprehensive analysis of photovoltaic results combined with theoretical calculations has been provided to propose a working principle mechanism of electron transport in the investigated nanomaterials. Each metal ion used during the nanomaterials' synthesis caused a different effect on the DSSC performance resulting from the structure of their energy bandgap. TiO2 doped with Cu2+ and Mn2+ indicates a remarkable decrease in conductivity instead of TiO2:Ni2+. Therefore, the most effective nanomaterial for DSSC application turned out to be TiO2:0.4 %Ni2+ with a photoconversion efficiency improvement compared to standard P25 titania.

Nanostructured DyCrO3-rGO for efficient photocatalytic dye degradation and hydrogen generation

Dysprosium chromite (DyCrO3) nanoparticles and dysprosium chromite-reduced graphene oxide (DyCrO3-rGO) nanocomposite were synthesized by using a hydrothermal technique. The rGO incorporated DyCrO3-rGO photocatalyst demonstrated up to 87% efficiency to degrade rhodamine B dye which is higher than those of DyCrO3 and commercial Degussa P25 titania nanoparticles. DyCrO3-rGO also generated approximately 3 times greater amounts of hydrogen via water splitting compared to that produced by the P25 titania nanoparticles. The outcome of this investigation might be helpful for synthesizing rGO-based nanocomposite heterostructures for superior solar energy-driven applications.

Photodegradation of Congo Red by Modified P25-Titanium Dioxide with Cobalt-Carbon Supported on SiO2 Matrix, DFT Studies of Chemical Reactivity

Congo red is a hazardous material in the environment. The present work describes the synthesis of TiO2/CoC@SiO2-bipy (1) and TiO2/CoC@SiO2-phen (2) nanocomposites for the photodegradation of azo-dye Congo red (CR) dye in aqueous solution, by combining pure TiO2 with CoC@SiO2-bipy (s1) and CoC@SiO2-phen (s2) nanoparticles. The prepared nanocomposites were evaluated in term of photocatalytic activity rates in aqueous solution using CR. The nanocomposites TiO2/CoC@SiO2-bipy (1) and TiO2/CoC@SiO2-phen (2) were prepared from TiO2 (75%) and CoC@SiO2-bipy (s1) or CoC@SiO2-phen (s2) (25%) (weight ratio). Ultra-sonication and milling were used to prepare the heterogeneous nano catalysts. The pH, initial dye concentration, and catalyst dosage appeared to have a significant impact on the photocatalytic degradation performance. Molecular oxygen and other active species played a significant role in the photocatalyst degradation of CR with sunlight energy (UV-index 5.0). The chemical reactions were accelerated depending upon electrophilicity (ω) and energy gap (Eg) of azo dye species CR-N=N, CR-N=NH and CR=N-NH species which were calculated by density function theory (DFT). It can be concluded that the rate of electron–hole recombination of the TiO2 catalyst, when adding CoC@SiO2-bipy (s1) or CoC@SiO2-phen (s2), not only enhances the degradation but also effectively removes toxic dye molecules and their by-products. The newly prepared TiO2/CoC@SiO2-bipy (1) nanocomposites showed increased photocatalytic efficiency at low catalyst dose and faster rate of degradation of Congo red compared to TiO2/CoC@SiO2-phen (2) and TiO2 catalysts. The novel catalysts (1) and (2) can be easily separated by centrifugation and filtration, from the reaction mixture compared to TiO2.

Platinum-Decorated TiO2: One Step Fast Monometallic Impregnation and Plasma Effect on Nanoparticles

In the present work, N-TiO2−x/Pt was synthesized using a homemade nitrogen plasma (AC) discharge system. The overall procedure use of low-power nitrogen plasma (100 watts) with 1 and 2 h of plasma discharge to successfully impregnate platinum nanoparticles on P25 titanium dioxide. The obtained samples were characterized using X-ray diffraction (XRD), UV–Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscopy (HRTEM). The results reveal the incorporation of metallic Pt up to 2.9% on the surface of TiO2 by increasing the duration of plasma discharge by up to two hours with a constant power of 100 watts. Likewise, the incorporation of nitrogen atoms into a lattice crystal was also favored, confirming a direct relationship between the amount of Pt and nitrogen atoms introduced in TiO2 as a function of the duration of plasma treatment. By characterizing nanoparticles loaded on a N-TiO2−x/Pt surface, we show that joined platinum nanoparticles have two different patterns, and the boundary between these two regions coalesces. The results demonstrate that the use of nitrogen plasma to impregnate platinum nanoparticles on the surface of TiO2 to obtain N-TiO2−x/Pt allows wide and relevant physics and chemistry applications.

Synthesis of Thin Titania Coatings onto the Inner Surface of Quartz Tubes and Their Photoactivity in Decomposition of Methylene Blue and Rhodamine B

An evaporation-deposition coating method for coating the inner surface of long (>1 m) quartz tubes of small diameter has been studied by the introduction of two-phase (gas-liquid) flow with the gas core flowing in the middle and a thin liquid film of synthesis sol flowing near the hot tube wall. The operational window for the deposition of continuous titania coatings has been obtained. The temperature range for the deposition of continuous titania coatings is limited to 105–120 °C and the gas flow rate is limited to the range of 0.4–1.0 L min−1. The liquid flow rate in the annular flow regime allows to control the coating thickness between 3 and 10 micron and the coating porosity between 10% and 20%. By increasing the liquid flow rate, the coating porosity can be substantially reduced. The coatings were characterized by X-ray diffraction, N2 chemisorption, thermogravimetric analysis, and scanning electron microscopy. The coatings were tested in the photocatalytic decomposition of methylene blue and rhodamine B under UV-light and their activity was similar to that of a commercial P25 titania catalyst.

Photocatalytic water splitting ability of Fe/MgO-rGO nanocomposites towards hydrogen evolution

Photocatalytic water splitting has greatly stimulated as an ideal technique for producing hydrogen (H2) fuel by employing two renewable sources, i.e., water and solar energy. Here, we have adopted a facile hydrothermal approach for the successful synthesis of reduced graphene oxide (rGO) incorporated Fe/MgO nanocomposites followed by thermal treatment at inert atmosphere to investigate their ability for photodegradation and photocatalytic hydrogen evolution via water splitting. Transmission Electron Microscopy images of Fe/MgO-rGO nanocomposite ensured the distribution of Fe/MgO nanoparticles throughout rGO sheets. Notably, all rGO supported nanocomposites, especially the one, thermally treated at 500 °C at Argon (Ar) atmosphere has demonstrated significantly higher photocatalytic efficiency towards the photodegradation of a toxic textile dye, rhodamine B, than pristine MgO and commercially available Degussa P25 titania nanoparticles as well as other composites. Under solar irradiation, Fe/MgO-rGO (500) nanocomposite exhibited 86% degradation of rhodamine B dye and generated almost four times higher H2 via photocatalytic water splitting compared to commercially available P25 titania nanoparticles. This promising photocatalytic ability of the Fe/MgO-rGO(500) nanocomposite can be attributed to the improved morphological and surface features due to heat treatment at inert atmosphere as well as escalated charge carrier separation with increased light absorption capacity imputed to rGO incorporation.

Catalyst Recovery, Regeneration and Reuse during Large-Scale Disinfection of Water Using Photocatalysis

The deployment of photocatalysis for remediation of water has not yet been realized, although laboratory-scale studies have demonstrated promise. Accomplishing this requires the development of photocatalysis as a process, including studying its efficiencies in remedying water when high volumes of water are processed, and addressing the recovery, possible regeneration and reuse of the photocatalysts. To that end, this work is aimed at demonstrating the use of a custom-built mobile platform for disinfecting large quantities of water. The benchtop platform built is capable of processing 15.14 L (4 gallons) per minute of water, with possibility for further scale-up. Preliminary studies on the catalyst recovery, regeneration and reuse via gravity-assisted settling, centrifugation and air plasma treatment indicated that 77% of Aeroxide® P25 titania (TiO2) nanoparticle and 57% of porous TiO2 nanowire photocatalysts could be recovered and regenerated for further use. Overall, this study indicated that process improvements, including increasing the kinetics of the photocatalysis, and optimization of the efficacies of the catalyst recovery and regeneration processes will make it useful for water remediation on any scale. More importantly, the portable and flexible nature of the benchtop photocatalysis system makes it amenable for use in conjunction with existing technologies for remedying large quantities of water.

Rare-Earth-Modified Titania Nanoparticles: Molecular Insight into Synthesis and Photochemical Properties.

A molecular precursor approach to titania (anatase) nanopowders modified with different amounts of rare-earth elements (REEs: Eu, Sm, and Y) was developed using the interaction of REE nitrates with titanium alkoxides by a two-step solvothermal–combustion method. The nature of an emerging intermetallic intermediate was revealed unexpectedly for the applied conditions via a single-crystal study of the isolated bimetallic isopropoxide nitrate complex [Ti2Y(iPrO)9(NO3)2], a nonoxo-substituted compound. Powders of the final reaction products were characterized by powder X-ray diffraction, scanning electron microscopy–energy-dispersive spectroscopy, Fourier transform infrared, X-ray photoelectron spectroscopy, Raman spectroscopy, and photoluminescence (PL). The addition of REEs stabilized the anatase phase up to ca. 700 °C before phase transformation into rutile became evident. The photocatalytic activity of titania modified with Eu3+ and Sm3+ was compared with that of Degussa P25 titania as the control. PL studies indicated the incorporation of Eu and Sm cations into titania (anatase) at lower annealing temperatures (500 °C), but an exclusion to the surface occurred when the annealing temperature was increased to 700 °C. The efficiency of the modified titania was inferior to the control titania while illuminated within narrow wavelength intervals (445–465 and 510–530 nm), but when subjected to a wide range of visible radiation, the Eu3+- and Sm3+-modified titania outperformed the control, which was attributed both to doping of the band structure of TiO2 with additional energy levels and to the surface chemistry of the REE-modified titania.

Does Symmetry Control Photocatalytic Activity of Titania-Based Photocatalysts?

Decahedral anatase particles (DAPs) have been prepared by the gas-phase method, characterized, and analyzed for property-governed photocatalytic activity. It has been found that depending on the reaction systems, different properties control the photocatalytic activity, that is, the particle aspect ratio, the density of electron traps and the morphology seem to be responsible for the efficiency of water oxidation, methanol dehydrogenation and oxidative decomposition of acetic acid, respectively. For the discussion on the dependence of the photocatalytic activity on the morphology and/or the symmetry other titania-based photocatalysts have also been analyzed, that is, octahedral anatase particles (OAP), commercial titania P25, inverse opal titania with and without incorporated gold NPs in void spaces and plasmonic photocatalysts (titania with deposits of gold). It has been concluded that though the morphology governs photocatalytic activity, the symmetry (despite its importance in many cases) rather does not control the photocatalytic performance.

Advantages of the Incorporation of Luffa-Based Activated Carbon to Titania for Improving the Removal of Methylene Blue from Aqueous Solution

This research aims to study the possible improvement of methylene blue (MB) removal from aqueous solution by hybrid adsorbent-catalysts (AdsCats) prepared through the incorporation of activated carbon derived from Luffa cylindrica fibers (LAC) to TiO2 photocatalysts. LAC with a specific surface area of 1170 m2/g was prepared by chemical activation with phosphoric acid at 500 °C. TiO2/LAC composites with 70 and 90 wt.% Degussa P25 titania content were prepared. The materials were characterized by N2 physical adsorption, XRD, FTIR, and XPS. The AdsCats displayed a very good dispersion of TiO2 over LAC, a surface area of close to 200 or 400 m2/g, depending on the composition, and high crystallinity, showing the presence of anatase and rutile phases. MB removal was studied in two different scenarios: under UV-light after reaching adsorption equilibrium, and under UV-light once the liquid effluent and the AdsCats were in contact. The MB removal by LAC has proved to be very efficient, highlighting the predominant role of adsorption over photodegradation. The prepared AdsCats have also been compared with their components. The results showed that TiLAC hybrids have superior photocatalytic performance than P25, showing TiLAC-7/3 90% MB removal with respect to the initial concentration just after 30 min of UV light irradiation for both studied scenarios.

Low levels of TiO2-nanoparticles interact antagonistically with Al and Pb alleviating their toxicity

The contamination and bioavailability of deleterious metals in arable soils significantly limits crop development and yield. Aiming at mitigating Pb- and Al-induced phytotoxicity, this work explores the use of P25 titanium dioxide nanoparticles (nTiO2) in soil amendments. For that, Lactuca sativa L. plants were germinated and grown in the presence of 10 ppm Pb or 50 ppm Al, combined or not with 5 ppm nTiO2. Growth parameters, as well as endpoints of the redox state [cell relative membrane permeability (RMP), thiobarbituric acid reactive substances content, total phenolic content and photosynthesis (sugars and pigments levels, chlorophyll a fluorescence and gas exchange), were evaluated. Concerning Al, nTiO2 treatment alleviated the impairments induced in germination rate, seedling length, water content, RMP, stomatal conductance (gs), intercellular CO2 (Ci), and net CO2 assimilation rate (PN). It increased anthocyanins contents and effective efficiency of photosystem II (ΦPSII). In Pb-exposed plants, nTiO2 amendment mitigated the effects in RMP, PN, gs, and Ci. It also increased the pigment contents and the transpiration rate (E) comparatively to the control without nTiO2. These results clearly highlight the high potential of low doses of nTiO2 in alleviating metal phytotoxicity, particularly the one of Pb. Additionally, further research should explore the use of these nanoparticles in agricultural soil amendments.