Evaluation of the adsorption potential of titanium dioxide nanoparticles for arsenic removal

The adsorption potential of titanium dioxide （TiO2） nanoparticles for removing arsenic from drinking water was evaluated. Pure and iron-doped TiO2 particles are synthesized via sol-gel method. The synthesized TiO2 nanoparticles were then immobilized on ordinary sand for adsorption studies. Adsorption isotherms were conducted on the synthesized nanoparticles as well as the sand coated with TiO2 nanoparticles under varying conditions of air and light, namely, the air-sunlight （A-SL）, air-light （AL）, air-dark （AD） and nitrogen-dark （ND）. X-ray diffraction （XRD） analysis showed that the pure and iron-doped TiO2 nanoparticles were in 100% anatase crystalline phase with crystai sizes of 108 and 65 nm, respectively. Adsorption of arsenic on the three adsorbents was non-linear that could be described by the Freundlich and Langmuir adsorption models. Iron doping enhanced the adsorption capacity of TiO2 nanoparticles by arresting the grain growth and making it visible light responsive resulting in a higher affinity for arsenic. Similarly, the arsenic removal by adsorption on the sand coated with TiO2 nanoparticles was the highest among the three types of sand used. In all cases, As（V） was adsorbed more compared with As（Ⅲ）. The solution pH appeared to be the most important factor in controlling the amount of arsenic adsorbed.

Effect of titanium dioxide nanoparticles on zebrafish embryos and developing retina

AIM: To investigate the impact of titanium dioxide nanoparticles(Ti O2NPs) on embryonic development and retinal neurogenesis.METHODS: The agglomeration and sedimentation of Ti O2 NPs solutions at different dilutions were observed,and the ultraviolet-visible spectra of their supernatants were measured. Zebrafish embryos were experimentally exposed to Ti O2 NPs until 72 h postfertilization(hpf). The retinal neurogenesis and distribution of the microglia were analyzed by immunohistochemistry and whole mount in situ hybridization.RESULTS: The 1 mg/L was determined to be an appropriate exposure dose. Embryos exposed to Ti O2 NPs had a normal phenotype. The neurogenesis was initiated on time, and ganglion cells, cones and rods were well differentiated at 72 hpf. The expression of fms m RNA and the 4C4 antibody, which were specific to microglia in the central nervous system(CNS), closely resembled their endogenous profile.CONCLUSION: These data demonstrate that short-term exposure to Ti O2 NPs at a low dose does not lead to delayed embryonic development or retinal neurotoxicity.

Microstructure and photocatalytic activity of titanium dioxide nanoparticles

Titanium dioxide nanoparticles with an average diameter of about 10 nm are fabricated using a sintering method. The degradation of methyl orange indicates that the photocatalytic efficiency is greatly enhanced, which is measured to be 62.81%. Transmission electron microscopy is used to investigate the microstructure of TiO2 nanoparticles in order to correlate their photocatalytic properties. High-resolution transmission electron microscopy examinations show that all the nanoparticles belong to the anatase phase, and pure edge dislocations exist in some nanoparticles. The great enhancement of photocatalytic efficiency is attributed to two factors, the quantum size effect and the surface defects in the nanoparticles.

Effect of Dissolved Organic Matter on Titanium Dioxide Nanoparticles in Aquatic Environment:Molecular Weight Fractions

At present,a growing number of consumer products contain engineered nanoparticle TiO2(nano⁃TiO2),which has resulted in the consequences of nano⁃TiO2 entering the aquatic environment directly or indirectly at some stage.The fate of nano⁃TiO2 in the aquatic environment has become the key factor which affects its safety application and nanoecotoxicology.This paper aims to investigate how the dissolved organic matters(DOM),especially the molecular weight fractions in the aquatic environment,affect the aggregation,stability,and fate of nano⁃TiO2,and the interaction mechanism of DOM and nano⁃TiO2.Results of dynamic light scattering(DLS)showed that the molecular weight of DOM molecules caused different aggregation rates of nano⁃TiO2 in aqueous solution.Fourier Transform infrared spectroscopy(FTIR)results indicated the molecular structure is characteristics of DOM fractions and the mechanisms of bonds formation between DOM and nano⁃TiO2.Results of three⁃dimensional excitation⁃emission matrices(3D⁃EEM)confirmed the FTIR results and implied the increase of the stability of theπ-πconjugated system in the presence of DOM.In addition,low molecular weight of DOM fractions appeared to show more affinity with nano⁃TiO2 than high molecular weight fractions.

Differential effect of aqueous Desmodium gangeticum root extract mediated TiO2 nanoparticles on isolated mitochondria, cells and Wistar rats

Objective: To study the renal toxic effect of titanium dioxide nanoparticles(TiNPs)prepared by chemical and green route.Methods: TiNPs were prepared by chemical(sol gel technique) and green route(using aqueous extract of Desmodium gangeticum root by using titanium tetraisopropoxide as precursor). Thus prepared TiNPs were characterized using UV–visible spectrophotometry, X-ray diffractometry and evaluated its renal toxic impact in different experimental models viz., Wistar rats(100 mg/kg b.wt.; oral), LLC-PK1 cells(100 mg/m L) and isolated renal mitochondria(0.25, 0.5 and 1 mg/m L).Results: Compared to the chemically synthesized TiNPs, Desmodium gangeticum synthesized nanoparticles showed less nephrotoxicity, determined by elevated serum renal markers like urea(62%), creatinine(35%), aspartate aminotransferase(61%) and alanine transaminase(37%) and the result was in agreement with cellular toxicity(measured by MTT assay and lactate dehydrogenase activity). Further toxicity evaluation at the level of mitochondria showed not much significant difference in TiNPs effect between two synthetic routes.Conclusions: The biochemical findings in renal tissue and epithelial cell(LLC-PK1)supported by histopathology examination and isolated mitochondrial activity showed minor toxicity with TiNPs prepared by green route(Ti NP DG) than TiNP Chem.

Modeling and numerical analysis of nanoliquid (titanium oxide, graphene oxide) flow viscous fluid with second order velocity slip and entropy generation

The prime objective of the present communication is to examine the entropy-optimized second order velocity slip Darcy–Forchheimer hybrid nanofluid flow of viscous material between two rotating disks.Electrical conducting flow is considered and saturated through Darcy–Forchheimer relation.Both the disks are rotating with different angular frequencies and stretches with different rates.Here graphene oxide and titanium dioxide are considered for hybrid nanoparticles and water as a continuous phase liquid.Joule heating,heat generation/absorption and viscous dissipation effects are incorporated in the mathematical modeling of energy expression.Furthermore,binary chemical reaction with activation energy is considered.The total entropy rate is calculated in the presence of heat transfer irreversibility,fluid friction irreversibility,Joule heating irreversibility,porosity irreversibility and chemical reaction irreversibility through thermodynamics second law.The nonlinear governing equations are first converted into ordinary differential equations through implementation of appropriate similarity transformations and then numerical solutions are calculated through Built-in-Shooting method.Characteristics of sundry flow variables on the entropy generation rate,velocity,concentration,Bejan number,temperature are discussed graphically for both graphene oxide and titanium dioxide hybrid nanoparticles.The engineering interest like skin friction coefficient and Nusselt number are computed numerically and presented through tables.It is noticed from the obtained results that entropy generation rate and Bejan number have similar effects versus diffusion parameter.Also entropy generation rate is more against the higher Brinkman number.

Long-term exposure to titanium dioxide nanoparticles promotes diet-induced obesity through exacerbating intestinal mucus layer damage and microbiota dysbiosis

Titanium dioxide nanoparticles (TiO2-NPs) are commonly used as food additives, including some high-fat foods that are risk factors for obesity. However, little is known about the effects of chronic TiO2-NPs digestion in the population on high fat diet (HFD). Herein, we reported that TiO2-NPs exacerbated HFD-induced obesity by disruption of mucus layer and alterations of gut microbiota. Oral intake of TiO2-NPs significantly increased body weight, liver weight, and amount of adipose tissues, especially in HFD-fed mice. Mechanistic studies revealed TiO2-NPs induced colonic mucus layer disruption and obesity-related microbiota dysbiosis. The damage on mucus was demonstrated through down-regulation of Muc2 gene and the absorption of mucin protein by TiO2-NPs. Consequently, mucus layer damage combined microbiota dysbiosis escalated the low-grade systemic inflammation, which exacerbated HFD-induced obesity. In contrast, gut microbiota depletion eliminated these effects, indicating gut microbiota were necessary for TiO2-NPs-induced inflammation and obesity. All the results stated the alarming role of TiO2-NPs in the HFD-driven obesity and emphasized the reevaluating the health impacts of nanoparticles commonly used in daily life, particularly, in susceptible population.

A mechanistic study of ciprofloxacin adsorption by goethite in the presence of silver and titanium dioxide nanoparticles

The adsorption behaviors of ciprofloxacin(CIP),a fluoroquinolone antibiotic,onto goethite(Gt)in the presence of silver and titanium dioxide nanoparticles(AgNPs and TiO_(2)NPs)were investigated.Results showed that CIP adsorption kinetics in Gt with or without NPs both followed the pseudo-second-order kinetic model.The presence of AgNPs or TiO_(2)NPs inhibited the adsorption of CIP by Gt.The amount of inhibition of CIP sorption due to AgNPs was decreased with an increase of solution pH from 5.0 to 9.0.In contrast,in the presence of TiO_(2)NPs,CIP adsorption by Gt was almost unchanged at pHs of 5.0∼6.5 but was decreased with an increase of pH from 6.5 to 9.0.The mechanisms of AgNPs and TiO_(2)NPs in inhibiting CIP adsorption by Gt were different,which was attributed to citrate coating of AgNPs resulting in competition with CIP for adsorption sites on Gt,while TiO_(2)NPs could compete with Gt for CIP adsorption.Additionally,CIP was adsorbed by Gt or TiO_(2)NPs through a tridentate complex involving the bidentate inner-sphere coordination of the deprotonated carboxylic group and hydrogen bonding through the adjacent carbonyl group on the quinoline ring.These findings advance our understanding of the environmental behavior and fate of fluoroquinolone antibiotics in the presence of NPs.

A case study of aggregation behaviors of titanium dioxide nanoparticles in the presence of dodecylbenzene sulfonate in natural water

The present work aims to ascertain the mechanisms of surfactant（dodecylbenzene sulfonate; DBS） effects on the aggregation behaviors of TiO2 nanoparticles（TiO2-NPs） in natural water samples. Aggregation experiments were conducted at a TiO2-NPs concentration of 10 mg/L in deionized water and in natural water samples via dynamic light scattering and Zeta potential determination. Average attachment efficiency was calculated to compare the aggregation behaviors of nanoparticles in the two aqueous media. Results showed that the effects of DBS on aggregation could be interpreted by both Derjaguin–Landau–Verwey–Overbeek（DLVO） and non-DLVO mechanisms. In natural water samples,aggregation did not occur rapidly and was able to develop slowly under all conditions, and the roles of DBS were obvious at high DBS concentration owing to the impacts of inherent components of natural water samples, such as colloids and natural organic compounds.Future aggregation studies should concentrate on multi-factor, multi-colloidal and dynamic aspects under similar environmental conditions.

Dielectric spectroscopy characterization of Naþ ion-conducting polymer nanocomposite system PEO–PVP–NaIO_(4)–TiO_(2)

We studied the effect of titanium dioxide(TiO_(2))nanoparticles(NPs)on dielectric behavior of Naþion-conducting salt-complexed polymer nanocomposite system formed from a binary polymer blend of poly(ethylene oxide)(PEO)and polyvinyl pyrrolidone(PVP),with the addition of both sodium metaperiodate(NaIO_(4))at concentration 10 wt.%and TiO_(2) NPs of size10 nm,at concentrations 1,2,3,4 and 5 wt.%.Free standing nanocomposite PEO/PVP/NaIO_(4)/TiO_(2) films(150m)were characterized at room-temperature by analyzing their complex electrical impedance and dielectric spectra in the range 1 Hz–1 MHz.At the concentration of 3 wt.%of TiO_(2) NPs,both ion conductivity and dielectric permittivity of the PEO/PVP/NaIO_(4)/TiO_(2) ion-conducting dielectrics reach an enhancement by more than one order of magnitude as compared to nanoadditive-free case.

Comparative cytotoxicity of nanoparticles and ions to Escherichia coli in binary mixtures

The objective of this study was to understand toxicity of mixture of nanoparticles （NPs） （ZnO and TiO2） and their ions to Escherichia coll. Results indicated the decrease in percentage growth of E. coli with the increase in concentration of NPs both in single and mixture setups. Even a small concentration of I mg/L was observed to be significantly toxic to E. coli in binary mixture setup （exposure concentration： 1 mg/L ZnO and 1 mg/L TiO2; 21.15% decrease in plate count concentration with respect to control）. Exposure ofE. coli to mixture of NPs at 1000 mg/L （i.e., 1000 mg/L ZnO and 1000 mg/L TiO2） resulted in 99.63% decrease in plate count concentration with respect to control. Toxic effects of ions to E. coli were found to be lesser than their corresponding NPs. The percentage growth reduction was found to be 36% for binary mixture of zinc and titanium ions at the highest concentration （i.e., 803.0 mg/L Zn and 593.3 mg/L Ti where ion concentrations are equal to the Zn ions present in 1000 mg/L ZnO NP solution and Ti＋4 ions present in 1000 mg/L TiO2 NP solution）. Nature of mixture toxicity of the two NPs to E. coli was found to be antagonistic. The alkaline phosphatase （Alp） assay indicated that the maximum damage was observed when E. coli was exposed to 1000 mg/L of mixture of NPs. This study tries to fill the knowledge gap on information of toxicity of mixture of NPs to bacteria which has not been reported earlier.

Effect of TiO_2 nanoparticle aggregation on marine microalgae Isochrysis galbana

TiO2 nanoparticles（NPs） could adversely impact aquatic ecosystems. However, the aggregation of these NPs could attenuate this effect. In this work, the biological effects of TiO2 NPs on a marine microalgae Isochrysis galbana were investigated. The aggregation kinetics of TiO2 NPs under different conditions was also investigated to determine and understand these effects. Results showed that, though TiO2 NPs had no obvious impact on the size and reproducibility of algal cells under testing conditions, they caused a negative effect on algal chlorophyll, which led to a reduction in photosynthesis. Furthermore, fast aggregation of TiO2 NPs occurred under all conditions, especially at the pH close to the p Hzpc. Increasing ionic strength and NP concentration also enhanced the aggregation rate.The aggregation and the following sedimentation of TiO2 NPs reduced their adverse effects on I. galbana.

Toxicological effects of TiO_(2) nanoparticles on plant growth promoting soil bacteria

Emerging contaminants like metal nanoparticles get introduced into soil through different routes.Toxic effects of these contaminants on plant growth-promoting bacteria(PGPB),which influence plant productivity,can be detrimental to soil health.Titanium dioxide is one of the most produced nanomaterials in the world and therefore potentially the most released nanoform in soil.The objective of this study was to evaluate the toxic effects of titanium dioxide nanoparticles(TiO2 NPs)on plant growth-promoting bacteria.Three types of PGPB,viz.,nitrogen fixers,phosphate solubilizers and biofilm formers were exposed to TiO2 NPs.Our results suggest that direct contact of the bacteria with these NPs is inhibitory as compared to when these bacteria are growing in laboratory nutrient media in the presence of NPs.The inhibitory effect did not follow a linear dose response but instead showed a pronounced step response.Soils with their varying characteristics may not afford the same protection to bacteria as laboratory nutrient media and thus TiO2 NPs may cause some sensitive PGPB to disappear from soil.The resultant shift in bacterial community composition may affect ecosystem functioning.

Toxic effects of nano-TiO_(2)in bivalves——A synthesis of meta-analysis and bibliometric analysis

Since the beginning of the 21 st century,the increasing production and application of nano-TiO_(2)in consumer products have inevitably led to its release into aquatic systems and therefore caused the exposure of aquatic organisms,resulting in growing environmental concerns.However,the safety of nano-TiO_(2)in aquatic environments has not been systematically assessed,especially in coastal and estuary waters where a large number of filterfeeding animals live.Bivalves are considered around the world to be a unique target group for nanoparticle toxicity,and numerous studies have been conducted to test the toxic effects of nano-TiO_(2)on bivalves.The aim of this review was to systematically summarize and analyze published data concerning the toxicological effects of nano-TiO_(2)in bivalves.In particular,the toxicity of nano-TiO_(2)to the antioxidant system and cell physiology was subjected to meta-analysis to reveal the mechanism of the toxicological effects of nano-TiO_(2)and the factors affecting its toxicological effects.To reveal the cooperation,hot keywords and cocitations in this field,bibliometric analysis was conducted,and the results showed that the toxicological molecular mechanisms of nano-TiO_(2)and the combined effects of nano-TiO_(2)and other environmental factors are two major hot spots.Finally,some perspectives and insights were provided in this review for future research on nano-TiO_(2)toxicology in bivalves.