Role of Surface Area, Primary Particle Size, and Crystal Phase on Titanium Dioxide Nanoparticle Dispersion Properties (original) (raw)
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The widespread use of titanium dioxide nanoparticles (TiO2NPs) in consumer products has led to an increase of their concentrations in the environment. For reliable determination of their total concentrations, the microwave assisted digestion procedure for the decomposition of nanoscale anatase and rutile was optimized and Ti concentrations were determined by inductively coupled plasma mass spectrometry (ICP-MS). To determine the TiO2NP concentration in environmental water samples, sample treatments, which maintain NPs dispersed and stabilized in solution, enabling quantitative transfer of TiO2NPs during the analytical procedure, are of crucial importance. In the present work, several dispersion approaches by the use of different mechanical and ultrasonication procedures in combination with various dispersing agents were examined in order to prepare aqueous suspensions of stable and homogeneously dispersed TiO2NPs. Experiments were performed with commercially available rutile and ana...
Journal of Nanoparticle Research, 2013
The recent detection of titanium dioxide nanoparticles (n-TiO 2) in wastewaters raised concerns about its fate in the aquatic environment, which is related to its mobility through water bodies. Laboratory experiments of n-TiO 2 (particle size distribution: 10-65 nm) dispersed into both synthetic and real aqueous solutions under environmentally realistic concentrations (0.01, 0.1, 1 and 10 mg/l) were conducted over a time of 50 h to mimic duration of ecotoxicological tests. Agglomeration and sedimentation behaviour were measured under controlled conditions of salinity (0-35 %), ionic composition and strength, pH and dissolved organic carbon (DOC). Physico-chemical parameters and particle agglomeration in the dispersions were investigated by transmission electron microscopy, Brunauer, Emmett and Teller method and dynamic light scattering. A fluorescence spectrophotometer operating in the nephelometric mode was employed to obtain the sedimentation rates of n-TiO 2. The overall results showed that agglomeration and sedimentation of n-TiO 2 were affected mainly by the initial concentration. Sedimentation data fitted satisfactorily (R 2 in the range of 0.74-0.98; average R 2 : 0.90) with a first-order kinetic equation.The settling rate constant, k, increased by approx. one order of magnitude by moving from the lowest to the highest concentration, resulting very similar especially for all dispersions at 1(k = 8 9 10-6 s-1) and 10 mg/l (k = 2 9 10-5 s-1) n-TiO 2 , regardless the ionic strength and composition of dispersions. The implication of these results on toxicological testing is discussed.
Environmental Science & Technology, 2009
The extensive use of titanium dioxide nanoparticles (nano-TiO 2 ) in many consumer products has raised concerns about possible risks to the environment. The magnitude of the threat may depend on whether nano-TiO 2 remains dispersed in the environment, or forms much larger-sized aggregates or clusters. Currently, limited information is available on the issue. In this context, the purpose of the present article is to report initial measurements of the morphology and rate of formation of nano-TiO 2 aggregates in aqueous suspensions as a function of ionic strength and of the nature of the electrolyte in a moderately acid to circumneutral pH range typical of soil and surface water conditions. Dynamic light scattering results show that 4-5 nm titanium dioxide particles readily form stable aggregates with an average diameter of 50-60 nm at pH ∼4.5 in a NaCl suspension adjusted to an ionic strength of 0.0045 M. Holding the pH constant, but increasing the ionic strength to 0.0165 M, leads to the formation of micron-sized aggregates within 15 min. At all other pH values tested (5.8-8.2), micron-sized aggregates form in less than 5 min (minimum detection time), even at low ionic strength (0.0084-0.0099 M with NaCl). In contrast, micronsized aggregates form within 5 min in an aqueous suspension of CaCl 2 at an ionic strength of 0.0128 M and pH of 4.8, which is significantly faster than observed for NaCl suspensions with similar ionic strength and pH. This result indicates that divalent cations may enhance aggregation of nano-TiO 2 in soils and surface waters. Optical micrographs show branching aggregates of sizes ranging from the 1 µm optical limit of the microscope to tens of micrometers in diameter.
Influence of ionic strength, pH, and cation valence on aggregation kinetics of TiO2 nanoparticles
2008
The extensive use of titanium dioxide nanoparticles (nano-TiO 2 ) in many consumer products has raised concerns about possible risks to the environment. The magnitude of the threat may depend on whether nano-TiO 2 remains dispersed in the environment, or forms much larger-sized aggregates or clusters. Currently, limited information is available on the issue. In this context, the purpose of the present article is to report initial measurements of the morphology and rate of formation of nano-TiO 2 aggregates in aqueous suspensions as a function of ionic strength and of the nature of the electrolyte in a moderately acid to circumneutral pH range typical of soil and surface water conditions. Dynamic light scattering results show that 4-5 nm titanium dioxide particles readily form stable aggregates with an average diameter of 50-60 nm at pH ∼4.5 in a NaCl suspension adjusted to an ionic strength of 0.0045 M. Holding the pH constant, but increasing the ionic strength to 0.0165 M, leads to the formation of micron-sized aggregates within 15 min. At all other pH values tested (5.8-8.2), micron-sized aggregates form in less than 5 min (minimum detection time), even at low ionic strength (0.0084-0.0099 M with NaCl). In contrast, micronsized aggregates form within 5 min in an aqueous suspension of CaCl 2 at an ionic strength of 0.0128 M and pH of 4.8, which is significantly faster than observed for NaCl suspensions with similar ionic strength and pH. This result indicates that divalent cations may enhance aggregation of nano-TiO 2 in soils and surface waters. Optical micrographs show branching aggregates of sizes ranging from the 1 µm optical limit of the microscope to tens of micrometers in diameter.
Environmental science & technology, 2016
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To exploit the advantages of nanoparticles for various applications, controlling the dispersion and agglomeration is of paramount importance. Agglomeration and dispersion behavior of titanium dioxide (TiO 2) nanoparticles was investigated using electrokinetic and surface chemical properties. Nanoparticles are generally stabilized by the adsorption of a dispersant (polyelectrolyte) layer around the particle surface and in this connection ammonium salt of polymethacrylic acid (Darvan C) was used as dispersant to stabilize the suspension. The dosages of polyelectrolyte were optimized to get best dispersion stability by techniques namely particle charge detector (13.75 mg/g) and adsorption (14.57 mg/g). The surface charge of TiO 2 particles changed significantly in presence of dispersant Darvan C and isoelectric point (iep) shifted significantly towards lower pH from 5.99 to 3.37. The shift in iep has been quantified in terms of free energy of interaction between the surface sites of TiO 2 and the adsorbing dispersant Darvan C. Free energies of adsorption were calculated by electrokinetic data (−9.8 RT unit) and adsorption isotherms (−10.56 RT unit), which corroborated well. The adsorption isotherms are of typical Langmuir type and employed for calculation of free energy. The results indicated that adsorption occurs mainly through electrostatic interactions between the dispersant molecule and the TiO 2 surface apart from hydrophobic interactions.
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DOE analyses on aqueous suspensions of TiO2 nanoparticles
Journal of the European Ceramic Society, 2008
Nanosized titanium oxide (TiO 2 ) powders have been prepared by conventional and microwave hydrothermal methods by forced hydrolysis of TiOCl 2 . As-prepared powders have been completely characterised by qualitative and quantitative XRD and TEM. The obtained titania powders have been redispersed (45 and 60 wt.%) in an aqueous hydroxypropylcellulose (HPC) solution (0.5-1 wt.%). Rheological characterisation has been performed in order to evaluate the influence of HPC on particles agglomerations. The effect of mixing time, HPC and TiO 2 concentration and their mutual interactions on shear stress have been evaluated with a design of experiment (DOE) approach.