Concentration Of TiO2 Nanoparticles Research Articles

Improving the stability of nanofluids via surface-modified titanium dioxide nanoparticles for wettability alteration of oil-wet carbonate reservoirs

The main challenge of the application of nanofluids for enhanced oil recovery (EOR) in oil-wet carbonate reservoirs is maintaining their stability under high-temperature and high-salinity which is normally seen in reservoir conditions. In this work, surface-modified TiO2 nanoparticles were synthesized by N-(2-Aminoethyl)−3-Aminopropyltrimethoxysilane (AEAPTMS) as a coupling agent for surface modification of nanoparticles. Zeta potential and dynamic light scattering analyses were used to evaluate the stability of the prepared nanofluids. Results indicated that nanofluids had high stability in 90 °C and 20 wt% salinity. The influence of nanofluids on wettability alteration of carbonate rocks was studied by measuring the contact angle value. Untreated rock samples were strongly oil-wet, with water advancing and receding contact angles of 165.1° and 166.2°, respectively. After treatment with 3wt% concentration of surface-modified TiO2 nanoparticles, the rock plate wettability changed to a water-wet state, with water advancing and receding contact angles of 37.6° and 48.2°, respectively. Suggested surface-modified TiO2 nanoparticles were more effective in wettability alteration of the rock surfaces compared to the un-modified TiO2 nanoparticles. Furthermore, higher concentration of nanoparticles, higher the ability of the nanoparticles on changing the rock wettability.

Titanium dioxide nanoparticles as a risk factor for the health of Neotropical tadpoles: a case study of Dendropsophus minutus (Anura: Hylidae)

The production and use of titanium dioxide (TiO2) nanoparticles are increasing worldwide. The release of this substance into the environment can induce toxic effects in aquatic invertebrates and vertebrates, although the exact nature of its impacts on Neotropical amphibians is still poorly understood. In this context, the present study evaluated the toxicity of TiO2 nanoparticles and their counterpart-dissolved titanium dioxide (TiO2)-in the tadpoles of Dendropsophus minutus. The biometric parameters, DNA damage, and behavioral changes were verified in tadpoles exposed to three different concentrations (0.1mg·L-1, 1.0mg·L-1, and 10mg·L-1) of TiO2 nanoparticles and dissolved TiO2 for 7days. We verified significant DNA damage in the D. minutus tadpoles exposed to both forms of Ti, in comparison with the control group. We also identified a reduction in total size, body length, and width, and the height of the musculature of the tail of the tadpoles exposed to all concentrations of both substances in comparison with the control. In the behavioral test, the tadpoles exposed to nanoparticles and dissolved TiO2 presented reduced mobility and a tendency to be less aggregated than normal. Here, the simultaneous use of multiple biomarkers was fundamental for the reliable assessment of the adverse effects of nanomaterials on anuran amphibians and the establishment of a systematic approach to the biomonitoring of aquatic ecosystems. The present study expands our understanding of the genotoxic, morphological, and behavioral effects of TiO2 nanoparticles and dissolved TiO2 on anuran amphibians, and contributes to the establishment of further research for the more systematic assessment of the environmental risk of nanomaterials.

Assessment of Thermophysical Performance of Ester-Based Nanofluids for Enhanced Insulation Cooling in Transformers

Nanotechnology provides an effective way to upgrade the thermophysical characteristics of dielectric oils and creates optimal transformer design. The properties of insulation materials have a significant effect on the optimal transformer design. Ester-based nanofluids (NF) are introduced as an energy-efficient alternative to conventional mineral oils, prepared by dispersing nanoparticles in the base oil. This study presents the effect of nanoparticles on the thermophysical properties of pure natural ester (NE) and synthetic ester (SE) oils with temperature varied from ambient temperature up to 80 °C. A range of concentrations of graphene oxide (GO) and TiO2 nanoparticles were used in the study to upgrade the thermophysical properties of ester-based oils. The experiments for thermal conductivity and viscosity were performed using a TC-4 apparatus that follows Debby’s concept and a redwood viscometer apparatus that follows the ASTM-D445 experimental standard, respectively. The experimental results show that nanoparticles have a positive effect on the thermal conductivity and viscosity of oils which reduces with an increase in temperature.

Influence of different concentrations of titanium dioxide and copper oxide nanoparticles on water sorption and solubility of heat-cured PMMA denture base resin.

ObjectivesThis study aimed to evaluate the effect of different concentrations of titanium dioxide (TiO2) and copper oxide (CuO) nanoparticles on the water sorption and solubility of heat‐cured polymethyl methacrylate (PMMA).Materials and MethodsFifty disc‐shaped specimens (10 × 2 mm) of heat‐cured PMMA were prepared and divided into five groups (n = 10) to be modified with 2.5 wt.% or 7.5 wt.% of either TiO2 or CuO nanoparticles. One group was left unmodified, serving as the control group. Water sorption and solubility were measured by weighing the specimens before and after immersion in distilled water and desiccation. The data were analyzed by using one‐way ANOVA and Tukey's post hoc test (α = .05).ResultsThe 2.5 wt.% CuO nanoparticles significantly decreased the water sorption (p = .016), but did not change the water solubility (p = .222) compared with the control group. The 7.5 wt.% CuO and both concentration of TiO2 nanoparticles did not change the water sorption, but significantly increased the solubility of heat‐cured PMMA (p ≤ .05).ConclusionAdding 2.5 wt.% CuO nanoparticles to heat‐cured PMMA decreases the water sorption; although, it has no significant effect on the solubility. Likewise, 2.5 and 7.5 wt.% TiO2 and 7.5 wt.% CuO do not affect the water sorption, but increase the water solubility of heat‐cured PMMA.Clinical SignificanceReinforcing the heat‐cured PMMA denture base resin materials with the right concentration and type of nanoparticles can decrease the water sorption of resin base materials, and consequently can influence the durability of dentures.

Combined effects of nanoparticles and ultrasonic field on thermal energy storage performance of phase change materials with metal foam

To further improve the performance of thermal energy storage (TES) system with phase change materials (PCMs), this paper proposed a novel method, i.e. combining the additions of TiO2 nanoparticles, metal foam and the provision of ultrasonic field, investigated its synergetic effects in enhancing conduction and convection heat transfer. The thermal characteristics, including the TES time distributions and the energy consumption of the TES system, were discussed to evaluate the combined effects of TiO2 nanoparticles and ultrasonic field on the TES rate and TES efficiency. The results showed that the latent TES time reduction index reached 46.50%, when the TiO2 nanoparticles concentration was 5.0 wt% and the ultrasonic power was 100 W, while the TES efficiency dropped to 10.66%. Increasing TiO2 nanoparticles concentration and ultrasonic power positively improved the TES rate due to conduction heat transfer enhanced by nanoparticles and convection heat transfer enhanced by the acoustic streaming effect and the cavitation effect of the ultrasonic field, but which negatively reduced the TES efficiency mainly due to the energy consumption of the ultrasonic field. Therefore, the effects of the ultrasonic field introduced at four action stages on the TES rate and TES efficiency were compared, and it confirmed that introducing ultrasonic field at the latent TES stage was better than that in the sensible TES stage. Additionally, the proposed novel combined method needed to consider the priority relationship between TES rate and TES efficiency for designing the TES system, favoring the potentials for further advances in TES applications.

Experimental study on the absorption enhancement of CO2 by MDEA‐MEA based nanofluids

AbstractNanofluids promote the application of nanotechnology in the mass transfer process, which can effectively reduce mass transfer resistance and increase the gas–liquid mass transfer rate. A bubbling absorption system was used to explore the CO2 absorption performance of methyldiethanolamine (MDEA) and monoethanolamine (MEA) blended nanofluids. TiO2 nanoparticles and sodium polyacrylate (ASAP) surfactant were added to MDEA‐MEA aqueous solutions to prepare nanofluids. The effects of MDEA concentration, MEA concentration, blended amine ratio, and nanoparticle solid content on CO2 capture performance were investigated, respectively. The study found that, compared with single‐component MEA/MDEA solutions, nanofluids have a more significant enhancement in CO2 absorption of blended amines. The increase of MEA concentration in blended amine has a negative effect on the enhanced CO2 absorption of TiO2 nanoparticles. The enhancement factor of MDEA‐MEA nanofluids at each solid content is higher than that of two single‐component nanofluids. The best solid content of TiO2 nanoparticles in the MDEA‐MEA system is 0.6 g/L, while the enhancement factor E in 25% MDEA + 5% MEA nanofluids can reach up to 1.36. Finally, a new empirical formula was proposed to predict the enhancement factor and optimum solid content of TiO2‐MEA/MDEA nanofluids.

Effect of the Lubrication on the Friction Characteristics of EN AW-2024-T3 Aluminium Alloy Sheets

The article presents the results of friction tests conducted on EN AW-2024 Alclad aluminium alloy sheets. The lubrication efficiency of oleic acid, mineral and vegetable oils with the addition of SiO2 and TiO2 nanoparticles was determined using the strip drawing test to assess the friction conditions in the flange area in the deep drawing process. The samples in the form of sheet metal strips were pulled between countersamples with a rounded surface at a speed of 2.5 mm/s. Gear oil and oleic acid demonstrated the lowest value of the coefficient of friction (COF) in the whole range of nominal pressures investigated. The lowest efficiency in reducing the COF was shown by hydraulic oil, olive oil and machine oil. A high content of TiO2 nanoparticles (0.5-0.9%wt%) is beneficial in the friction process involving oleic acid.

3D Laser Nanoprinting of Optically Functionalized Structures with Effective-Refractive-Index Tailorable TiO2 Nanoparticle-Doped Photoresin.

The advanced direct laser printing of functional devices with tunable effective index is a key research topic in numerous emerging fields, especially in micro-/nano-optics, nanophotonics, and electronics. Photosensitized nanocomposites, consisting of high-index materials (e.g., titanium dioxide, TiO2) embedded in polymer matrix, are emerging as attractive platforms for advanced additive manufacturing. Unfortunately, in the currently applied techniques, the preparation of optically functionalized structures based on these photosensitized nanocomposites is still hampered by many issues like hydrolysis reaction, high-temperature calcinations, and, especially, the complexity of experimental procedures. In this study, we demonstrate a feasible strategy for fabricating micro-/nanostructures with a flexibly manipulated effective refractive index by incorporating TiO2 nanoparticles in the matrix of acrylate resin, i.e., TiO2-based photosensitized nanocomposites. It was found that the effective refractive index of nanocomposite can be easily tuned by altering the concentration of titanium dioxide nanoparticles in the monomer matrix. For TiO2 nanoparticle concentrations up to 30 wt%, the refractive index can be increased over 11.3% (i.e., altering from 1.50 of pure monomer to 1.67 at 532 nm). Based on such a photosensitized nanocomposite, the grating structures defined by femtosecond laser nanoprinting can offer vivid colors, ranging from crimson to magenta, as observed in the dark-field images. The minimum printing width and printing resolution are estimated at around 70 nm and 225 nm, indicating that the proposed strategy may pave the way for the production of versatile, scalable, and functionalized opto-devices with controllable refractive indices.

Titanium dioxide nanoparticles affect somatic embryo initiation, development, and biochemical composition in Paulownia sp. seedlings

Paulownia is a fast-growing tree with multiple uses. The present study was conducted to determine the most appropriate concentration of TiO2 nanoparticles (titanium dioxide) for the induction of somatic embryogenesis and regeneration, reduction of free radicals, and the increase of antioxidant enzymes. Variables examined included explants (leaf and petiole), Paulownia species (Paulownia shantung, Paulownia elongate and Paulownia fortune), and concentrations of TiO2 nanoparticle. The results showed significant effect of TiO2 on callus induction for all the three species. For Paulownia shantung, the callus formation for the samples in the medium containing 60 mg/L of TiO2 was 100% while for the samples in the control condition (without TiO2) it was 25%. The highest of somatic embryogenesis was observed for Paulownia shantung. However, the highest levels of flavonoids, anthocyanins, carotenoids, and chlorophyll a, b, and total chlorophyll were observed in induced and regenerated embryos at a concentration of 60 mg/L titanium dioxide nanoparticles. By increasing the concentration of TiO2, the amount of leaf soluble protein decreased. At the concentration of 60 mg/L TiO2 the density, number and regeneration of somatic embryo induction increased compared to the studied treatments. The largest ratio of seedling rooting was observed in ½MS (Reduction to half the entire MS medium content) supplemented with 1.5 mg/L IBA. The results can introduce lead to a novel protocol to proliferate healthy plantlets of Paulownia in a short time. Therefore, the present study led to the development of an effective and useful protocol for somatic embryo induction, regeneration, and increase of antioxidants in regenerated seedlings in the shortest time applying titanium dioxide concentration in the culture medium.

Evaluation Flexural Strength of PMMA Resins with the Addition of Nanoparticles

The flexural strength of heat cure acrylic resin was investigated by adding different concentrations of TiO2 and ZrO2 nanoparticles to increase its mechanical properties. ZrO2 and TiO2 nanoparticles were added at 1, 3, and 5% concentrations to the powder portion of heat polymerized acrylic resins. A total of 49 samples were prepared in 65 × 10 × 3 mm size. The structural characterisations of all experimental groups were determined by Fourier transform infrared spectroscopy. Flexural strength of the resin specimens was evaluated with a three-point bending test in a universal test machine and then examined under by scanning electron microscope to assess its topographic characteristics. The highest flexural strength value was obtained for 3% TiO2, while the lowest values were obtained for 1% and 5% TiO2. 1% ZrO2 and 3% TiO2 groups showed statistically higher flexural strength values than the control group. The addition of 3% and 5% ZrO2 and 1% and 5% TiO2 showed statistically lower flexural strength than the control group. The addition of ZrO2 and TiO2 nanoparticles for strengthening acrylic resin is directly related to the amount of concentration. The addition of 1% ZrO2 and 3% TiO2 is recommended to strengthen heat cure acrylic resin due to its high flexural strength values.

Experimental investigation on the effect of TiO2 nanoparticles on the performance of NH3 – H2O - LiBr absorption refrigeration system

The newly NH3 – H2O – LiBr working fluid can decrease the power wasted in the generator, thus improves the COP of the ammonia absorption refrigeration system. But the applying of NH3 – H2O – LiBr working fluid decreases the ammonia absorption efficiency, so the COP of the system is still unsatisfactory. To further enhance the COP of the NH3 – H2O - LiBr absorption refrigeration system, TiO2 nanoparticles are added to the NH3 – H2O - LiBr working fluid in this study. And the effects of TiO2 nanoparticles concentration on the performances of the generator, absorber, evaporator, condenser, and solution heat exchanger are tested in an ARS experimental system. The experimental results indicate that the addition of TiO2 nanoparticles increases the Pg, Pe, Pa, and Pc, meaning that the value of ammonia produced in the generator increases. Therefore, the COP and iCOP of the system are improved by adding TiO2 nanoparticles, and the COP is maximum improved by 18.96% compared with the ammonia-water absorption refrigeration system. When the xTiO2 is increased from 0.3% to 0.5%, the increase rate of the COP decreases because the newly added nanoparticles do not disperse well. So 0.3% is a better choice for the TiO2 nanoparticles concentration when comprehensively considering the dispersion stability of nanoparticles and the COP.

Entomotoxicity of TiO2 and ZnO Nanoparticles Against Adults Tribolium Castaneum (Herbest) (Coleoptera: Tenebrionidae)

The red flour beetle Tribolium castaneum is one of the common pests of stored grains distributed worldwide. In this study, testing the effect of TiO2 and ZnO nanoparticles as insecticides on adults of T. castaneum was achieved. Results showed that the high concentration of TiO2 and ZnO nanoparticles recorded high cumulative mortality of the adult insects after exposure time 1, 3, and 5 days from treatments 15.30, 23.57, and 29.85% respectively of TiO2 nanoparticles compared with 20.42, 27.08, and 33.96 % respectively of ZnO nanoparticles. The result showed that TiO2 and ZnO nanoparticles are effective in controlling and can be introduced in the future in integrated pest management of T. castaneum.

New Understanding of the Difference in Filtration Performance between Anatase and Rutile TiO2 Nanoparticles through Blending into Ultrafiltration PSF Membranes

The blending of nanomaterials into a polymeric matrix is a method known for its ability, under certain circumstances, to lead to an improvement in membrane properties. TiO2 nanoparticles have been used in membrane research for the last 20 years and have continuously shown promise in this field of research. Polysulfone (PSf) membranes were obtained through the phase inversion method, with different TiO2 nanoparticle concentrations (0, 0.1, 0.5, and 1 wt.%) and two types of TiO2 crystalline structure (anatase and rutile), via the addition of commercially available nanopowders. Research showed improvement in all studied properties. In particular, the 0.5 wt.% TiO2 rutile membrane recorded an increase in permeability of 139.7% compared to the control membrane. In terms of overall performance, the best nanocomposite membrane demonstrated a performance index increase of 71.1% compared with the control membrane.

Enhanced Electrical Properties of Crystalline Silicon Solar Cells via Nano-Composite Polyvinyl-Alcohol/Titanium Dioxide

Reflection loss and solar cell temperature both have a significant impact on solar cell efficiency and, consequently, on power generation. Herein, the aim is to investigate into the impact of Nanocomposite Titanium Dioxide (TiO2)/Polyvinyl Alcohol (PVA) on polycrystalline silicon solar cells. The solvent casting method is employed to prepare nanocomposite TiO2/PVA for deposition on the front side of the solar cell. The Tauc plot is used to investigate the influence of TiO2 nanoparticle concentration (10-20nm) on the energy bandgap of a nanocomposite. To test the optical properties of the solar cell after depositing the Nanocomposite coating film and to confirm the suspension of TiO2 in PVA and construct a Nanocomposite, an ultraviolet-visible spectrometer and a Fourier transform infrared spectrometer are provided. The results show that increasing the TiO2 in the TiO2/PVA Nanocomposite increases the energy bandgap. The Ultraviolet-Visible spectrometer observes that the Nanocomposite films absorb the Ultraviolet wavelength and transmittance at the visible wavelength. Finally, it found the lowest reflection obtained was 3.9% for 0.2wt% TiO2 in TiO2/PVA nanocomposite and the enhancement of the solar cell efficiency was (+2.3%).

Improved mechanical and electrochemical properties of PVDF/PEO/LiClO4 based solid polymer electrolyte by using TiO2 and MgO nanoparticles

The poly (vinylidene fluoride) PVDF and poly (ethylene oxide) PEO-based solid polymer electrolytes are gaining popularity due to their good electrochemical and mechanical characteristics. In the present work the polymer electrolyte is prepared by taking 80% PVDF, 20% PEO, and 20% LiClO4 through rigorous mixing. Further, the properties of PVDF/PEO/LiClO4 based electrolyte are improved by adding TiO2 and MgO nanoparticles in different proportions. The results show that the addition of TiO2 and MgO nanoparticles has a significant effect on the electrochemical characteristics and mechanical properties of the electrolyte. The maximum current onset potential of 4.97 V is observed with a 4% concentration of TiO2 nanoparticles. Also, the mechanical properties such as ultimate stress and failure stress are increased with the addition of nanoparticles. The ionic conductivity of the electrolyte first increases with an increase in the concentration of nanoparticles but it starts decreasing after 2% concentration.

Functionalization of PMMA/TiO2 nanocomposites: Synthesis, characterization and their antioxidant and antibacterial evaluation

AbstractThe present work reports the functionalization of PMMA and its nanocomposites were synthesized via simple solution mixing method. Functionalization of PMMA with different amino containing groups, that is, ethylene diamine (ED) and 4‐amino benzoic acid (PA) and used with low dosage (1 wt% and 3 wt%) of TiO2 nanoparticles (NPs) to form nanocomposites. The morphology was determined by SEM, average particle size (50 nm) of TiO2 NPs was measured by TEM. The pore radius (14.47 A°) and specific surface area (157.89 m2/g) of TiO2 NPs were measured by BET analysis. FT‐IR and NMR analysis confirms the functionalization of PMMA. The antioxidant activity of functionalized PMMA and its nanocomposites have been analyzed by using 2,2 diphenyl‐1‐picryhydrazyl (DPPH) assay. The antibacterial activity against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) of functionalized polymer nanocomposites were investigated. The result revealed that functionalized PMMA (PMPA) shows maximum antioxidant activity. The increase in concentration of TiO2 NPs efficiently augments the bacterial inhibition against Gram‐negative and Gram‐positive bacteria. The maximum zone of inhibition (ZOI) was recorded against E. coli ATCC 25922 (30 mm) and S. aureus ATCC 29213 (31 mm) and minimum inhibitory concentration (MIC) over E. coli (64 μg/ml) and S. aureus (32 μg/ml) by PMPA2. The synthesized functionalized PMMA nanocomposites can be considered as promising material for biological applications.

Antimicrobial Effect of Titanium Oxide (Tio2) Nano Particles in Completely Edentulous Patients. A Randomized Clinical Trial.

Objective: to investigate the effect of addition different concentration of TiO2 nanoparticles on acrylic resin polymethyl methacrylate to improve the anti-microbial properties of denture base material Subjects and Methods: 24 completely edentulous patients were selected to be enrolled in of the following groups: Group I: 8 patients were rehabilitated with complete dentures had no nanoparticle (Control group),Group II: 8 patients were rehabilitated with complete dentures had a 1% concentration of titanium oxide nanoparticles and Group III: 8 patients were rehabilitated with complete dentures had a 3% concentration of titanium oxide nanoparticles . Microbiological evaluation was done from the fitting surface of dentures after one week, two weeks, and one month of denture use. Results: Regarding staphylococcus aureus and candida albicans colonization, the result revealed that between one week, two weeks , and one month follow up periods for each group and between different groups for each follow up period, there was a statistically significant difference between all groups. Regarding staphylococcus epidermis colonization , there was negative colonization of staphylococcus epidermis . Conclusion: Addition of TiO2 nano particles with 1% and 3% concentrations to PMMA has a great anti-microbial effect with reduction of the colonization of S. aureus, S. epidermis and C. albicans than the conventional dentures

Effect of long-term low concentrations of TiO2 nanoparticles on dewaterability of activated sludge and the relevant mechanism: the role of nanoparticle aging.

Nanoparticles can undergo aging phenomena in sewage treatment systems, which alter their physical and chemical properties. However, the effect of aged nanoparticles on the dewatering performance of activated sludge under long-term low concentrations is yet to be reported in sewage treatment systems. Here, we compared the chronic effects of pristine and aged TiO2 nanoparticles on the sludge dewatering index, which includes specific resistance to filtration (SRF) and bound water (BW) in a sequencing batch reactor (SBR) at μg/L concentration levels, and analyzed the relevant mechanisms. The results indicated that aging in the sludge supernatant altered the photosensitivity and water stability of nanoparticles, which was mainly due to the changes in the zeta potential and energy band of the particle and was ultimately attributed to the combined effect of particle surface inclusions such as organic matter and inorganic salt. At 10 μg/L, nanoparticles reduced the sludge dewaterability, which observed an improvement at 100 μg/L. This is because 10 μg/L promoted the secretion of extracellular polymeric substances (EPS), which regulated the structure of sludge flora and increased the abundance of secreted quorum sensing-acyl-homoserine lactones (QS-AHL) and EPS genera, while the corresponding exposure results for 100 μg/L were the opposite, owing to the damage and necrosis effects caused by exposure under long-term light, which reduced EPS production and increased sludge density. Interestingly, aging could alleviate the effects of two exposure concentrations on sludge dewatering, mainly because of the decrease in the photoactivity of the nanoparticles. The results of this study show that environmental aging could delay, but not reverse the results of exposure to specific concentrations of nanoparticles. However, the significantly different ecological effects of photosensitive nanoparticles with two environmentally relevant concentration should be refined and confirmed again in freshwater environments to provide a basis for subsequent scientific management and control of photosensitive nanoparticles.

Ecotoxicological effects of dietary titanium dioxide nanoparticles on metabolic and biochemical parameters of model organism Galleria mellonella (Lepidoptera: Pyralidae)

Nanoparticles (NPs) are now being used in many industrial activities, such as mining, paint and glass industries. The frequent industrial use of NPs contributes to environmental pollution and may cause cellular and oxidative damage in native organisms. In this study, the toxic effects of titanium dioxide nanoparticles (TiO2 NPs) were investigated using Galleria mellonella larvae as a model insect species. Alterations in cell damage indicators, such as alanine transferase, aspartate transferase, lactate dehydrogenase, non-enzymatic antioxidants and biochemical parameters, were determined in the hemolymph of G. mellonella larvae exposed to TiO2 NPs at different concentrations (5, 50, 250 and 1250 μg/mL) in their diets. TiO2 NPs caused concentration-dependent cellular damage in the hemolymph of G. mellonella larvae and increased the levels of the non-enzymatic antioxidants uric acid and bilirubin. In addition, total protein in hemolymph significantly decreased at the highest concentration (1250 μg/mL) of TiO2 NPs. Level of the urea increased at the highest concentration (1250 μg/mL) of TiO2 NPs, whereas the amount of glucose was not affected. These findings demonstrated that TiO2 NPs caused concentration-dependent toxic effects on G. mellonella larvae.

Influence of wastewater type in the effects caused by titanium dioxide nanoparticles in the removal of macronutrients by activated sludge.

The imminent arrival of nanoparticles (NPs) to the wastewater treatment plants (WWTP) brings concern about their effects, which can be related to the wastewater composition. In this work, the effects of titanium dioxide (TiO2) NPs in the removal of carbon, nitrogen, and phosphorus by activated sludge bioreactors during the treatment of synthetic, raw, and filtered wastewaters were evaluated. Floc size, compaction of sludge, and morphological interactions between sludge and NPs were also determined. The main effect of TiO2 NPs was the inhibition of up to 22% in the removal of ammonia nitrogen for all types of wastewaters. This effect is strong dependent on combined factors of TiO2 NPs concentration and content of organic matter and ammonia in wastewater. The removal of dissolved organic carbon was affected by TiO2 NPs in lower level (up to 6%) than nitrogen removal for all types of wastewaters. Conversely to adverse effects, the removals of orthophosphate in the presence of TiO2 NPs were improved by 34%, 16%, and 55% for synthetic, raw, and filtered wastewater, respectively. Compaction of the sludge was also enhanced as the concentrations of NPs increased without alterations in the floc size for all types of wastewaters. Based on TEM and STEM imaging, the main interaction between TiO2 NPs and the activated sludge flocs was the adsorption of NPs on cell membrane. This means that NPs can be attached to cell membrane during aerobic wastewater treatment, and potentially disrupt this membrane. The effects of TiO2 NPs on macronutrient removal clearly depended on wastewater characteristics; hence, the use of realistic media is highly encouraged for ecotoxicological experiments involving NPs.