Transport and retention of engineered Al2O3, TiO2, and SiO2 nanoparticles through various sedimentary rocks.
ABSTRACT: Engineered aluminum oxide (Al2O3), titanium dioxide (TiO2), and silicon dioxide (SiO2) nanoparticles (NPs) are utilized in a broad range of applications; causing noticeable quantities of these materials to be released into the environment. Issues of how and where these particles are distributed into the subsurface aquatic environment remain as major challenges for those in environmental engineering. In this study, transport and retention of Al2O3, TiO2, and SiO2 NPs through various saturated porous media were investigated. Vertical columns were packed with quartz-sand, limestone, and dolomite grains. The NPs were introduced as a pulse suspended in aqueous solutions and breakthrough curves in the column outlet were generated using an ultraviolet-visible spectrophotometer. It was found that Al2O3 and TiO2 NPs are easily transported through limestone and dolomite porous media whereas NPs recoveries were achieved two times higher than those found in the quartz-sand. The highest and lowest SiO2-NPs recoveries were also achieved from the quartz-sand and limestone columns, respectively. The experimental results closely replicated the general trends predicted by the filtration and DLVO calculations. Overall, NPs mobility through a porous medium was found to be strongly dependent on NP surface charge, NP suspension stability against deposition, and porous medium surface charge and roughness.
Project description:A series of Cu catalysts supported on SiO2, Al2O3-SiO2, TiO2 rutile, and Cu/TiO2 anatase metal oxides has been studied for methanol reforming in the vapor phase. The highest activity was obtained on Cu/SiO2 catalysts (5493 ?mol H2 min-1·gcat -1) followed by Cu/TiO2 rutile, Cu/Al2O3-SiO2, and anatase. XRD and HRTEM characterization after reaction revealed that on Cu/SiO2 significant sintering occurred during reaction. In contrast, the particle size growth on Cu/TiO2 rutile and anatase was less pronounced, which could be associated with the interaction between Cu clusters and TiO2. Characterization by TGA showed that on Cu/Al2O3-SiO2 the main cause of deactivation was coke deposition.
Project description:Porous silica anti-reflection (AR) films are of importance in solar cells' photon harvest. However, the usual utilized method to fabricate AR films is the two-step method since the formation of porous silica NPs (first step) and silica coating sol (second step) always require chemical systems at distinct pH values. To reduce the complexity of the process, we choose cationic emulsion as an approach to produce the porosity and propose a convenient one-step route to get high-performance antireflective films. A single layer SiO2 anti-reflective (AR) film with high optical transmittance up to 97.5% at 740 nm was fabricated from composite sol that was made from cationic emulsion nanolatex and tetraethylorthosilicate under acid catalysis condition. After calcination, the transmittance of AR coated glasses still held the transmittance of 96% at 550 nm. Composited with SiO2, Al2O3, or TiO2 sol binders, the transmittance of AR coated glasses could be recovered as high as 97.9% at 650 nm and the pencil hardness was further strengthened up to 6H. The composite sol can keep stable at least one month at ambient temperature without any visible precipitation. Therefore, the proposed method is promising for developing high-performance AR films effectively and economically.
Project description:This dataset is related to the research article in Chemosphere, entitled ‘The limited facilitating effect of dissolved organic matter extracted from organic wastes on the transport of titanium dioxide nanoparticles in acidic saturated porous media’ . The data summarised the characterization of dissolved organic matter (DOM) extracted from organic wastes and their effects on the transport of titanium dioxide nanoparticles (TiO2 NPs) in acidic saturated porous media in the presence of monovalent electrolyte. Three types of dissolved organic matter were extracted from organic materials, including swine manure, sludge, and sediment, using deionized water, and were characterized with UV–Vis, FTIR and elementary analysis. The adsorption of DOM onto TiO2 NPs was evaluated in the presence of NaCl, and zeta potentials of TiO2 NPs were also determined. Breakthrough column experiments were conducted to quantify the effects of the extracted DOM on the transport behaviours of TiO2 NPs in acidic porous media compared with humic acid. Moreover, the interaction energy between nanoparticles and between nanoparticles and quartz media was calculated according to the classical DLVO theory. The dataset could be used as a reference for the evaluation and prediction of the environmental fate and subsequent risk of engineered nanomaterials.
Project description:The impact of pH and ionic strength on the mobility (individual and co-transport) and deposition kinetics of TiO2 and ZnO NPs in porous media was systematically investigated in this study. Packed column experiments were performed over a series of environmentally relevant ionic strengths with both NaCl (0.1-10 mM) and CaCl2 (0.01-0.1mM) solutions and at pH 5, 7, and 9. The transport of TiO2 NPs at pH 5 was not significantly affected by ZnO NPs in solution. At pH 7, a decrease in TiO2 NP transport was noted with co-existence of ZnO NPs, while at pH 9 an increase in the transport was observed. At pH 5 and 7, the transport of ZnO NPs was decreased when TiO2 NPs was present in the solution, and at pH 9, an increase was noted. The breakthrough curves (BTC) were noted to be sensitive to the solution chemistries; the decrease in the breakthrough plateau with increasing ionic strength was observed under all examined pH (5, 7, and 9). The retention profiles were the inverse of the plateaus of BTCs, as expected from mass balance considerations. Overall, the results from this study suggest that solution chemistries (ionic strength and pH) are likely the key factors that govern the individual and co-transport behavior of TiO2 and ZnO NPs in sand.
Project description:Nanoparticles (Nps) can induce toxicity in the lung by accidental or intentional exposure. The main objective of the study reported here was to characterize the effect that four metal oxide Nps (CeO2, TiO2, Al2O3 and ZnO) had at the cellular level on a human lung epithelial cell line. This goal was achieved by studying the capacity of the Nps to activate the main mitogen-activated protein kinases (MAPKs) and the nuclear factor NF?B. Only ZnO Nps were able to activate all of the MAPKs and the release of Zn2+ ions was the main cause of activation. ZnO and Al2O3 Nps activated the NF?B pathway and induced the release of inflammatory cytokines. CeO2 and TiO2 Nps were found to have safer profiles. The graphical abstract was obtained using Servier Medical Art.
Project description:In this work, SiO2 nanoparticles (NPs) were integrated into the mesoporous TiO2 layer of a perovskite solar cell to investigate their effect on cell performance. Different concentrations of SiO2/ethanol have been combined in TiO2/ethanol to prepare pastes for the fabrication of the mesoporous layer with which perovskite solar cells have been fabricated. Addition of SiO2 NPs of 50 and 100 nm sizes produces an enhancement of cell performance mainly because of an improvement of the photocurrent. This increment is in good agreement with the theoretical predictions based on light scattering induced by dielectric SiO2 NPs. The samples using modified scaffolds with NPs also present a significant lower current-potential hysteresis indicating that NP incorporation also affects the ion accumulation at the perovskite interface, providing an additional beneficial effect. The results stress the importance of the appropriated management of the optical properties on further optimization of perovskite solar cell technology.
Project description:The enormous technological relevance of titanium dioxide (TiO2) nanoparticles (NPs) and the consequent concerns regarding potentially hazardous effects that exposure during production, use, and disposal can generate, encourage material scientists to develop and validate intrinsically safe design solution (safe-by-design). Under this perspective, the encapsulation in a silica dioxide (SiO2) matrix could be an effective strategy to improve TiO2 NPs safety, preserving photocatalytic and antibacterial properties. In this work, A549 cells were used to investigate the toxic effects of silica-encapsulated TiO2 having different ratios of TiO2 and SiO2 (1:1, 1:3, and 3:1). NPs were characterized by electron microscopy and dynamic light scattering, and cell viability, oxidative stress, morphological changes, and cell cycle alteration were evaluated. Resulting data demonstrated that NPs with lower content of SiO2 are able to induce cytotoxic effects, triggered by oxidative stress and resulting in cell necrosis and cell cycle alteration. The physicochemical properties of NPs are responsible for their toxicity. Particles with small size and high stability interact with pulmonary cells more effectively, and the different ratio among silica and titania plays a crucial role in the induced cytotoxicity. These results strengthen the need to take into account a safe(r)-by-design approach in the development of new nanomaterials for research and manufacturing.
Project description:As the commercial use of synthetic amorphous silica nanomaterials (SiO2-NPs) increases, their effects on the environment and human health have still not been explored in detail. An often-insurmountable obstacle for SiO2-NP fate and hazard research is the challenging analytics of solid particulate silica species, which involves toxic and corrosive hydrofluoric acid (HF). We therefore developed and validated a set of simple hydrofluoric acid-free sample preparation methods for the quantification of amorphous SiO2 micro- and nanoparticles. To circumvent HF, we dissolved the SiO2-NPs by base-catalyzed hydrolysis at room temperature or under microwave irradiation using potassium hydroxide, replacing the stabilizing fluoride ions with OH-, and exploiting the stability of the orthosilicic acid monomer under a strongly basic pH. Inductively coupled plasma - optical emission spectroscopy (ICP-OES) or a colorimetric assay served to quantify silicon. The lowest KOH: SiO2 molar ratio to effectively dissolve and quantify SiO2-NPs was 1.2 for colloidal Stöber SiO2-NPs at a pH >12. Fumed SiO2-NPs (Aerosil®) or food grade SiO2 (E551) containing SiO2-NPs were degradable at higher KOH: SiO2 ratios >8000. Thus, hydrofluoric acid-free SiO2-NP digestion protocols based on KOH present an effective (recoveries of >84%), less hazardous, and easy to implement alternative to current methods.
Project description:Proteins are the most important component in sludge extracellular polymeric substances (EPS) and play a crucial role in the formation of sludge flocs, adsorption performance of sludge, and flocculation ability of sludge. This research is aimed at exploring the changes in proteins in EPS extracted from concentrated sludge after various nanoparticle (NP) treatments. The results showed that the protein content in EPS decreased by 40% after nanoalumina (Al2O3 NPs) treatment but increased at varying degrees after nanoferric oxide (Fe3O4 NPs), nanozinc oxide (ZnO NPs), and nanotitanium dioxide (TiO2 NPs) treatments. The four kinds of nanoparticles not only affected the protein content in EPS but also influenced the types and structures of proteins. The results of three-dimensional fluorescence spectroscopy showed that the tyrosine-like protein content in soluble EPS (SEPS) decreased after treatments with four kinds of NPs. Infrared spectroscopy analysis revealed that the absorption intensity of amide I and amide II weakened after Al2O3 NP treatment, whereas that of amide I enhanced after Fe3O4 NP, ZnO NP, and TiO2 NP treatments. Further analysis of the secondary structure of proteins in the infrared range of 1700-1600?cm-1 demonstrated that the value of ?-helix/(?-sheet+random coil) decreased from 0.513 to 0.383 in SEPS after TiO2 NP treatment. For the samples treated by Fe3O4 NPs, the percentage of ?-helix significantly increased and that of ?-sheet slightly decreased in proteins from SEPS and loosely bound EPS.
Project description:Engineered nanoparticles are used at an increasing rate in both industry and medicine without fully understanding their impact on health and environment. The nematode Caenorhabditis elegans is a suitable model to study the toxic effects of nanoparticles as it is amenable to comprehensive phenotyping, such as locomotion, growth, neurotoxicity and reproduction. In this study, we systematically evaluated the effects of silver (Ag) and five metal oxide nanoparticles: SiO2, CeO2, CuO, Al2O3 and TiO2. The results showed that Ag and SiO2 exposures had the most toxic effects on locomotion velocity, growth and reproduction, whereas CeO2, Al2O3 and CuO exposures were mostly neurotoxic. We further performed RNAseq to compare the gene expression profiles underlying Ag and SiO2toxicities. Gene set enrichment analyses revealed that exposures to Ag and SiO2consistently downregulated several biological processes (regulations in locomotion, reproductive process and cell growth) and pathways (neuroactive ligand-receptor interaction, wnt and MAPK signaling, etc.), with opposite effects on genes involved in innate immunity. Our results contribute to mechanistic insights into toxicity of Ag and SiO2 nanoparticles and demonstrated that C. elegans as a valuable model for nanotoxicity assessment.