Presence Of nano-TiO2 Research Articles

Treatment of malachite green dye using combined oxidation techniques based on different irradiation

We investigated the treatment of malachite green (MG) dye using sonocatalytic, photocatalytic and sonophotocatalytic techniques. The percentage of decolorization for sonophotolysis (65.5±3.3%) was much higher than the individual effects of sonolysis (55.2±2.4%) and photolysis (52.1±2.6%). The efficiency of the sonophotocatalytic process increased in the presence of photocatalysts such as anatase TiO2 (82.2±4.1%) and ZnO (75.7±3.8%). The decolorization rate further enhanced in the presence of nano-TiO2 (anatase, rutile ratio 75: 25 and particle size ≤100 nm). The enhancement in decolorization was marginal for sonophotocatalysis (95.9±4.8%) as compared to sonocatalysis (93.0±4.3%) and photocatalysis (93.2±4.6%). The intensification of decolorization in the presence of nano-TiO2, due to lower recombination of hydroxyl ions on the photocatalytic surface and nano-particle size of a catalyst, increased cavitational activity. The total organic carbon was found to be maximum for sonophotocatalytic in the presence of nano-TiO2 (67.1±3.3%).

Effect of Nano-TiO2 Additions on the Densification and Properties of Magnesite–Dolomite Ceramic Composites

Nano-titania, up to 8 wt%, was added to magnesite–dolomite refractory matrix. The phase and microstructure analyses of samples heated up to 1650 °C for 3 h were studied by XRD and SEM/EDS, respectively. The physical properties are reported in terms of bulk density, apparent porosity, and hydration resistance. In addition, the mechanical behavior was studied by a cold crushing strength (CCS), and flexural strength at 1200 °C test. As a result, it was found that the presence of nano-TiO2 in the magnesite–dolomite matrix induced titanates formation (Mg2TiO4 and CaTiO3), which improved the sintering process. Nano-titania influenced the bonding structure through a direct bonding enhancement. In general, the addition of 6 wt% of nano-TiO2 contributed to reach a maximum increment in physical and mechanical properties.

Nano-TiO2 affects Cu speciation, extracellular enzyme activity, and bacterial communities in sediments

In aquatic ecosystems, titanium dioxide nanoparticles (nano-TiO2) coexist with heavy metals and influence the existing forms and toxicities of the metal in water. However, limited information is available regarding the ecological risk of this coexistence in sediments. In this study, the effect of nano-TiO2 on Cu speciation in sediments was investigated using sequential extraction. The microcosm approach was also employed to analyze the effects of the coexistence of nano-TiO2 and Cu on extracellular enzyme activity and bacterial communities in sediments. Results showed that nano-TiO2 decreased the organic matter-bound fraction of Cu and increased the corresponding residual fraction Cu. As a result, speciation of exogenous Cu in sediments changed. During the course of the 30-day experiment, the presence of nano-TiO2 did not affect Cu-induced changes in bacterial community structure. However, the coexistence of nano-TiO2 and Cu restrained the activity of bacterial extracellular enzymes, such as alkaline phosphatase and β-glucosidase. The degree of inhibition also varied because of the different properties of extracellular enzymes. This research highlighted the importance of understanding and predicting the effects of the coexistence of nanomaterials and other pollutants in sediments.

Arsenate Accumulation, Distribution, and Toxicity Associated with Titanium Dioxide Nanoparticles in Daphnia magna.

Titanium dioxide nanoparticles (nano-TiO2) are widely used in consumer products. Nano-TiO2 dispersion could, however, interact with metals and modify their behavior and bioavailability in aquatic environments. In this study, we characterized and examined arsenate (As(V)) accumulation, distribution, and toxicity in Daphnia magna in the presence of nano-TiO2. Nano-TiO2 acts as a positive carrier, significantly facilitating D. magna's ability to uptake As(V). As nano-TiO2 concentrations increased from 2 to 20 mg-Ti/L, total As increased by a factor of 2.3 to 9.8 compared to the uptake from the dissolved phase. This is also supported by significant correlations between arsenic (As) and titanium (Ti) signal intensities at concentrations of 2.0 mg-Ti/L nano-TiO2 (R = 0.676, P < 0.01) and 20.0 mg-Ti/L nano-TiO2 (R = 0.776, P < 0.01), as determined by LA-ICP-MS. Even though As accumulation increased with increasing nano-TiO2 concentrations in D. magna, As(V) toxicity associated with nano-TiO2 exhibited a dual effect. Compared to the control, the increased As was mainly distributed in BDM (biologically detoxified metal), but Ti was mainly distributed in MSF (metal-sensitive fractions) with increasing nano-TiO2 levels. Differences in subcellular distribution demonstrated that adsorbed As(V) carried by nano-TiO2 could dissociate itself and be transported separately, which results in increased toxicity at higher nano-TiO2 concentrations. Decreased As(V) toxicity associated with lower nano-TiO2 concentrations results from unaffected As levels in MSFs (when compared to the control), where several As components continued to be adsorbed by nano-TiO2. Therefore, more attention should be paid to the potential influence of nano-TiO2 on bioavailability and toxicity of cocontaminants.

Does the presence of titanium dioxide nanoparticles reduce copper toxicity? A factorial approach with the benthic amphipod Gammarus fossarum

In aquatic ecosystems, titanium dioxide nanoparticles (nano-TiO2) may adsorb co-occurring chemical stressors, such as copper (Cu). This interaction has the potential to reduce the concentration of dissolved Cu due to surface binding to the nanoparticles. The subsequent sedimentation of nano-TiO2 agglomerates may increase the exposure of benthic species towards the associated Cu. This scenario was assessed by employing the amphipod Gammarus fossarum as model species and taking advantage of a 2×2-factorial design investigating absence and presence of 2mg nano-TiO2/L and 40μg Cu/L (n=45; t=24d) in darkness, respectively. Nano-TiO2 alone did not affect mortality and leaf consumption, whereas Cu alone caused high mortality (>70%), reduced leaf consumption (25%) and feces production (30%) relative to the control. In presence of nano-TiO2, Cu-induced toxicity was largely eliminated. However, independent of Cu, nano-TiO2 decreased the gammarids’ assimilation and weight. Hence, nano-TiO2 may be applicable as Cu-remediation agent, while its potential long-term effects need further attention.

The reduced bioavailability of copper by nano-TiO₂ attenuates the toxicity to Microcystis aeruginosa.

Nano-TiO2 is a widely applied nanoparticle (NPs) and co-exists with other pollutants such as heavy metals in aquatic environments. However, minimal knowledge is available concerning the ecological risk of these mixtures. Our study reported that at no toxic effect concentrations of TiO2 nanoparticles (5 mg/L), the toxicity of Cu ions to the algae Microcystis aeruginosa was significantly attenuated by TiO2 nanoparticles. Specifically, the concentration of photosynthetic pigments (i.e., concentration of Chla) increased 37% when comparing only Cu ions treated and the nano-TiO2-Cu co-incubation. The levels of phycocyanin (PC), allophycocyanin (APC), phycoerythrin (PE), and phycobiliprotein (PBPs) were also recovered at levels ranging from 23 to 35% after 72 h. For oxidative indexes, the decreased activities of the superoxide dismutase (SOD), peroxidase (POD) content, and malondialdehyde (MDA) with the existence of nano-TiO2 displayed a lower level compared to Cu ions treatment only at 24 and 48 h. This toxicity attenuation can be confirmed by subcellular structures because the impairment to cellular membranes and organelles reduced with the presence of nano-TiO2. The potential mechanisms of the antagonism between the nano-TiO2 and Cu ions can be partially attributed to the sorption of copper onto TiO2 nanoparticles, which fitted the Freundlich isotherm (coefficient = 0.967). The decreased bioavailability of Cu ions protected algae cells from being attacked by free Cu ions. Given the abundance of released nanoparticles and unique physicochemical property of nanoparticles, our results elucidated the ecosafety of nanoparticles and co-substrates in aquatic systems.

Fabrication of nano-TiO2/carbon nanotubes and nano-TiO2/nanocarbon black on alkali hydrolyzed polyester producing photoactive conductive fabric

In this paper, the alkali hydrolyzed polyester fabric was treated with functional single-wall and multi-wall carbon nanotubes, nanocarbon black without and with nano-TiO2 and citric acid as a cross-linking agent through exhaustion method and post-curing. Electrical conductivity, methylene blue degradation, UV protection, and thermal stability of the treated fabrics were investigated. The loading of various carbon nanostructures and nano-TiO2 on the polyester fabric confirmed with SEM images and energy-dispersive X-ray spectroscopy. Further, X-ray diffraction, remaining ash percentage via furnace and thermogravimetric analysis, proved the presence of nano-TiO2 on the polyester fabric. The UV protection verified with UV–Vis reflection spectra indicated the highest protection on the nanocarbon black/nano-TiO2/CA-treated fabric. The highest discoloration of methylene blue solution and electrical conductivity obtained on the treated fabric with functional single-wall carbonnano tube/nano-TiO2/citric acid and functional nanocarbon black/nano-TiO2/citric acid. This is related to enhance photocatalytic activities of nano-TiO2 with cooperation of single-wall carbon nanotubes and more surface coating of nanocarbon black on the polyester fabric.

Influence of titanium dioxide nanoparticles on 2,3,7,8-tetrachlorodibenzo-p-dioxin bioconcentration and toxicity in the marine fish European sea bass (Dicentrarchus labrax)

The present study investigated the influence of nano-TiO2 (1 mg L−1) on 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) (46 pg L−1) bioconcentration and toxicity in the European sea bass (Dicentrarchus labrax) during 7 days in vivo exposure. A multimarkers approach was applied in different organs: detoxification in liver; innate immunity and pro-inflammatory response and adaptive immunity in gills and spleen; genotoxicity in peripheral erythrocytes and muscle. Bioconcentration of 2,3,7,8-TCDD in presence of nano-TiO2 was investigated in liver, skin and muscle as well as interaction between nano-TiO2 and organic pollutants in artificial sea water (ASW). Nano-TiO2 negatively influenced immune response induced by 2,3,7,8-TCDD in spleen but not in gills and reduced the DNA damage induced by 2,3,7,8-TCDD in erythrocytes. nano-TiO2 did not interfere with 2,3,7,8-TCDD detoxification and bioconcentration according to the observed no interaction of the nano-TiO2 with organic pollutants in ASW.

Synthesis of 8-acetoxytetracyclo[4.4.12.5.17.10.01.6]dodec-3-ene and diesters of C1-C5 acids on its basis

Reaction of vinyl acetate with tricyclo[5.2.12.5.1.02.6]deca-3,8-diene in the presence of nano-TiO2 (20 nm) catalyst was studied. 8-Acetoxytetracyclo[4.4.12.5.17.10.01.6]dodec-3-ene was obtained in 88.5% yield. Addition of saturated monobasic acids C1-C5 to the obtained unsaturated monoester in the presence of the boron trifluoride etherate catalyst was investigated. Corresponding diesters were obtained in 68.1–93.0% yield. They can be used as the additives to synthetic oils and as components of perfumes.

Chemical interactions between Nano-ZnO and Nano-TiO2 in a natural aqueous medium.

The use of diverse engineered nanomaterials (ENMs) potentially leads to the release of multiple ENMs into the environment. However, previous efforts to understand the behavior and the risks associated with ENMs have focused on only one material at a time. In this study, the chemical interactions between two of the most highly used ENMs, nano-TiO2, and nano-ZnO, were examined in a natural water matrix. The fate of nano-ZnO in Lake Michigan water was investigated in the presence of nano-TiO2. Our experiments demonstrate that the combined effects of ZnO dissolution and Zn adsorption onto nano-TiO2 control the concentration of dissolved zinc. X-ray absorption spectroscopy was used to determine the speciation of Zn in the particulate fraction. The spectra show that Zn partitions between nano-ZnO and Zn2+ adsorbed on nano-TiO2. A simple kinetic model is presented to explain the experimental data. It integrates the processes of nano-ZnO dissolution with Zn adsorption onto nano-TiO2 and successfully predicts dissolved Zn concentration in solution. Overall, our results suggest that the fate and toxicity potential of soluble ENMs, such as nano-ZnO, are likely to be influenced by the presence of other stable ENMs, such as nano-TiO2.

Influence of Titanium Dioxide Particle Size on the Photostability of the Chemical UV-Filters Butyl Methoxy Dibenzoylmethane and Octocrylene in a Microemulsion

Sunscreen products often contain combinations of ultraviolet (UV)-filters in order to achieve broad spectrum protection from exposure to sunlight. The inclusion of both chemical and physical UV-filters in these products, however, increases the possibility for both photolytic and photocatalytic reactions to occur. This study investigated the effect of titanium dioxide (TiO2) particle size on the photostability of the chemical UV-filters butyl methoxy dibenzoylmethane (BMDM) and octocrylene (OC) formulated in a microemulsion. The International Conference on Harmonisation (ICH) Guideline Q1B for photostability testing of new active substances and medicinal products was applied. BMDM and OC in the microemulsion were irradiated with simulated sunlight in the presence of nano- (&lt;25 nm) and micro-TiO2 (~0.6 μm) and their concentrations determined using a validated high performance liquid chromatography (HPLC) method. For the combination of BMDM and OC, the photodegradation for BMDM was found to be 12% higher in the presence of nano-TiO2 as compared to that of the micro-TiO2. This enhanced photodegradation is attributed to the larger surface area of the nano-TiO2 and the increased generation of reactive oxygen species (ROS). Because of these findings, sunscreen products containing chemical UV-filters and nano-TiO2 should be regarded with caution, due to the potential loss of photoprotection.

Species sensitivity and dependence on exposure conditions impacting the phototoxicity of TiO₂ nanoparticles to benthic organisms.

Toxicity of titanium dioxide nanoparticles (nano-TiO2 ) to aquatic organisms can be greatly increased after exposure to ultraviolet (UV) radiation. This phenomenon has received some attention for water column species; however, investigations of nano-TiO2 phototoxicity for benthic organisms are still limited. In the present study, bioassays of 3 representative benthic organisms (Hyalella azteca, Lumbriculus variegatus, and Chironomus dilutus) were conducted to evaluate nano-TiO2 phototoxicity. When exposed to 20 mg/L of nano-TiO2 and various light intensities (0-30 W/m(2)), H. azteca was the most sensitive, with a median lethal dose of 40.7 (95% confidence interval, 36.3-44.7) Wh/m(2), and hence is a potential model organism in future toxicological guidelines for photoactive nanomaterials to freshwater benthos. Without the presence of nano-TiO2 , no mortality was observed in L. variegatus and C. dilutus exposed to UV intensity ranging from 0 W/m(2) to 41 W/m(2). However, a sharp drop of H. azteca survival was observed when UV intensity was higher than 9.4 W/m(2), demonstrating the importance of UV-only effects on the ultimate phototoxicity of nanomaterials. Furthermore, both bioavailability and surface attachment of nano-TiO2 onto organisms were affected by the exposure scenario, supported by the exposure scenario-dependent phototoxicity seen in H. azteca and C. dilutus. Overall, the present study demonstrates the importance of species sensitivity and exposure scenarios in future test guidelines of nano-phototoxicity.

Nano-TiO&lt;sub&gt;2&lt;/sub&gt; as a novel and efficient catalyst for the synthesis of pyridine dicarbonitriles

Pyridine dicarbonitriles have been synthesized in good yields via a one-pot multi–component reaction of aldehyde, malononitrile, and thiol in the presence of nano-TiO2 as a catalyst in ethanol. KEY WORDS: Pyridine dicarbonitriles, Multi–component reaction, One-pot, Nano-TiO2 Bull. Chem. Soc. Ethiop. 2014, 28(1), 149-153.DOI: http://dx.doi.org/10.4314/bcse.v28i1.18

“Protective” Effects of Titanium Dioxide Nano-particles on Daphnia magna Exposed to UV Radiation

Aims: Titanium dioxide nano-particles (nano-TiO2) have been used in sunscreen creams to protect skin againstultra violet (UV) radiation; other applications are polarized glasses, wall paints, etc., however, the ecological risks when nano-TiO2 residues reach aquatic ecosystems is not well documented; therefore, the objective of this study is to give some insight on the attenuating effects of nano-TiO2 against UV radiation on Daphnia magna and the toxicity of nano-TiO2 on this organism. Study Design: Exposing Daphnis to UV radiation in presence and absence of nano-TiO2. Place and Duration of Study: Biotechnology Institute, CNR, Canada and Toxicology laboratory, Faculty of Marine Sciences, University of Sinaloa Mexico; between April and July 2012. Methodology: Daphnis (adults and neonates) were exposed to UV light for varying periods in the absence and presence of nano-TiO2. After 48 h incubation, mortalities were recorded for each experiment. Similar experiments were performed using bulk TiO2 instead of nano-TiO2, to know if protective effect is related to particles size. Finally, to Original Research Article British Journal of Applied Science & Technology, 4(12): 1858-1868, 2014 1859 know if protective effect is outer (blocking UV radiation) or interior (by cellular processes), Daphnis were pre-treated with nano-TiO2, then exposed to UV radiation, and mortalities recorded. Results: The mortalities were significantly lower in presence than in absence of nanoTiO2. Alsomortalities were significantly higher in bulk TiO2 than in nano-TiO2, indicating that nano-TiO2has a protective effect against UV radiation on Daphnis. Also, results indicate that protective effect is exterior, by blocking of UV rather than cellular repair mechanisms (cellular processes). However, at 100mg/L nanoTiO2 concentration, 15% mortality was observed. Conclusion: Nano-TiO2 is a nanomaterial blocking UV radiation; however if residues reach aquatic ecosystems, could be a risk (toxic) for aquatic organisms, because the highest concentration used in this work caused mortalities in Daphnia magna.

Sonochemical degradation of chlorobenzene in the presence of additives

The present work deals with establishing the pathway for the selection of additives for intensification of the sonolytic degradation of chlorobenzene. The degradation of chlorobenzene has been investigated in the presence of different additives such as CuO, TiO2, nano-TiO2 and NaCl. The reaction has been monitored in terms of the concentration of the parent pollutant as well as the extent of mineralization. The first-order kinetic rate constant for the removal of chlorobenzene has been evaluated for different loadings of additives. It has been observed that the extent of degradation and mineralization was maximum in the presence of nano-TiO2 and minimum in the presence of CuO. A three-step mechanism has been developed for the degradation of chlorobenzene based on the identification of intermediates. The removal of chloride from the benzene ring due to pyrolysis was the dominant mechanism with minimal contribution from the attack of hydroxyl radical present in the bulk of solution. The oxidation products also react subsequently with the hydroxyl radicals resulting in mineralization. The rate of mineralization has been quantified in terms of total organic carbon removal. The observed trends for the mineralization confirm that the extent of mineralization depends on the ease of generation of hydroxyl radicals.

Incorporation of nano TiO2 in black rice husk ash mortars

In this study, untreated black rice husk ash (BRHA) was employed as cement replacement in fractions of 10%, 20% and 30%. Dosages of 0.5%, 1.0% and 1.5% nano TiO2 were added into blended cement to study the mechanical properties and microstructural changes in mortars. The mechanical properties were studied using compressive and ultrasonic pulse velocity tests. XRD, SEM, TGA and DSC were conducted to investigate the chemical composition and microstructural changes of BRHA mortars with the presence of nano TiO2. The results showed that nano TiO2 in BRHA blended cement improved the mechanical properties and microstructure of BRHA mortars.

Synergistic effects of nano-sized titanium dioxide and zinc on the photosynthetic capacity and survival of Anabaena sp.

Anabaena sp. was used to examine the toxicity of exposure to a nano-TiO2 suspension, Zn2+ solution, and mixtures of nano-TiO2 and Zn2+ suspensions. Typical chlorophyll fluorescence parameters, including effective quantum yield, photosynthetic efficiency and maximal electron transport rate, were measured by a pulse-amplitude modulated fluorometer. Nano-TiO2 particles exhibited no significant toxicity at concentrations lower than 10.0 mg/L. The 96 h concentration for the 50% maximal effect (EC50) of Zn2+ alone to Anabaena sp. was 0.38 ± 0.004 mg/L. The presence of nano-TiO2 at low concentrations (<1.0 mg/L) significantly enhanced the toxicity of Zn2+ and consequently reduced the EC50 value to 0.29 ± 0.003 mg/L. However, the toxicity of the Zn2+/TiO2 system decreased with increasing nano-TiO2 concentration because of the substantial adsorption of Zn2+ by nano-TiO2. The toxicity curve of the Zn2+/TiO2 system as a function of incremental nano-TiO2 concentrations was parabolic. The toxicity significantly increased at the initial stage, reached its maximum, and then decreased with increasing nano-TiO2 concentration. Hydrodynamic sizes, concentration of nano-TiO2 and Zn2+ loaded nano-TiO2 were the main parameters for synergistic toxicity.

Efficient preparation of 9-aryl-1,8-dioxo-octahydroxanthenes catalyzed by nano-TiO2with high recyclability

9-Aryl-1,8-dioxo-octahydroxanthene derivatives are synthesized by the reaction of arylaldehydes with dimedone (5,5-dimethyl-1,3-cyclohexanedione) in the presence of nano-TiO2 as an efficient and heterogeneous catalyst under solvent-free conditions. Simple methodology, easy workup procedure, clean reaction, short reaction time, reusability of the catalyst up to 12 times and high yields are some advantages of this work.

The influence of ZnO and TiO2nanoparticles on the toxicity of sewage sludges

More and more often sewage sludges become the place of deposition of nanoparticles (NPs), the use of which in consumer products is increasing. In turn, the increasing amount of sewage sludges enforces the need for their utilization (e.g. through the application of sludges to the soil). Therefore, the presence of NPs in sewage sludges may create a new threat to the environment. Thus it becomes important to perform evaluation of the toxicity of sewage sludges in the context of their content of NPs. The objective of the study was to estimate the effect of nanoparticles of ZnO (nano-ZnO) and TiO2 (nano-TiO2) and their bulk counterparts (bZnO and bTiO2) on the toxicity of sewage sludges in relation to selected organisms (plants – Lepidium sativum and Sinapis alba, and microorganisms – Vibrio fischeri and 11 different strains from Microbial Assay for Risk Assessment – MARA). The study also involved the estimation of other factors that may have an effect on the phytotoxicity of NPs in sewage sludge: the size of the particles, the dose of the sewage sludge, the time of NP–sewage sludge contact and light conditions. The effect of both nano-ZnO and nano-TiO2 on the toxicity of the sludges is dependent on the kind of NPs and their concentration. Sludges containing NPs displayed a different level of toxicity from their bulk counterparts. All of the factors estimated (size of particles, dose of sludge, contact time and light conditions) had a significant effect on the phytotoxicity of NPs which was dependent both on the kind of the NPs and on that of the sewage sludge. Estimation of the leachate toxicity indicated a greater sensitivity of plants to the presence of NPs as compared to the sensitivity of microorganisms. Leachates caused a greater reduction of bioluminescence of V. fischeri in the presence of nano-TiO2 than nano-ZnO. Nano-ZnO caused a reduction of the toxicity of the sewage sludge leachates.

Performance of dimethyl dioxirane/nano-TiO2 on epoxidation of polybutadiene and hydroxyl terminated polybutadiene

Polybutadiene and hydroxyl terminated polybutadiene (HTPB) were epoxidized using in situ-generated dimethyl dioxirane (DMD) as an oxidant in the presence of nano-TiO2 at 25°C. Reaction time and different percentages of catalyst/Oxone® (w/w) were also examined. The capability of different kinds of double bonds to be epoxidized was studied in detail at various reaction times, and the products were characterized using nuclear magnetic resonance (1HNMR), 13CNMR, and Fourier transform infrared (FT-IR) techniques, with no side reaction being detected. The results indicate that using nano-TiO2 as a catalyst increases the epoxidation yield, especially of cis double bonds.