Search results for "solution"

An improved numerical solver of the 2D diffusive shallow waters equations over unstructured triangular meshes

2009

Determination of the crystallinity of TiO2 photocatalysts

2018

Abstract This study reports a new simple method to determine the crystallinity of anatase and rutile TiO2 photocatalysts. The crystallinity degree of various anatase and rutile samples was estimated by XRD analysis from the ratio among the full width at half maximum intensities of the main diffraction peaks of anatase or rutile and the (111) peak of CaF2 as internal standard. The photocatalytic activity of selected powders was tested employing the photodegradation of 4-nitrophenol in aqueous solution as probe reaction. The results showed that the photoactivity of the investigated samples increased with increasing crystallinity and crystallite size.

Photocatalytic activity of nanocrystalline TiO2 (brookite, rutile and brookite-based) powders prepared by thermohydrolysis of TiCl4 in aqueous chlori…

2008

Abstract Nanocrystalline TiO2 powders were synthesized by thermohydrolysis of TiCl4 in HCl or NaCl aqueous solutions. Rutile, mixtures of brookite and rutile or mixtures of anatase, brookite and rutile were obtained depending on the acidity of the medium. Crystalline phases and composition of the mixtures were identified by using XRD analysis. Pure brookite nanoparticles, separated from the mixtures of brookite and rutile by simple peptization with water, were stable against transformation to rutile up to 750 °C. The prepared TiO2 powders were characterized by thermal analysis, diffuse reflectance spectroscopy and BET surface area determinations. The band gap of bulky brookite was estimated…

Photoactivity of Nanostructured TiO2 Catalysts in Aqueous System and their Surface Acid-Base, Bulk and Textural Properties

2007

This work reports on the characterisation and determintion of the photocatalytic activity of some TiO2 catalysts prepared using TiCl4 as precursor. The samples, consisting of suspensions, dispersions or powders of nanonstructured anatase or rutile phases, were obtained in very mild conditions, i.e., by boiling the solution obtained after hydrolysis of TiCl4 at atmospheric pressure: it is worth noting that no calcination was necessary to obtain photoactive phases. The samples were characterised by X-ray diffraction (XRD), determination of the BET specific surface area (SSA), scanning electron microscopy (SEM) observations and diffuse reflectance spectroscopy (DRS). FT-IR spectroscopy was use…

Photocatalytic degradation of phenol in aqueous titanium dioxide dispersions

1988

The results of a study of photocatalytic degradation of phenol using aqueous oxygenated TiO2 (anatase) suspensions in a batch Pyrex photoreactor are reported. The influence on the photodegradation rate of various parameters as pH, phenol and TiO2 content, oxygen partial pressure, anions present in the dispersions was investigated. A complete oxidation of phenol was observed. Intermediate compounds, catechol and quinone, were detected. It was observed that the photodegradation also proceeded with sunlight radiation. A mechanistic and kinetic model, which accounts for the results obtained, is given. Likely reasons for inactivity of the rutile modification for this reaction are also given.

Photocatalytic degradation of carbaryl in aqueous TiO2 suspensions containing surfactants

1999

The effect of ionic and non-ionic aliphatic surfactants on the photocatalytic degradation of Carbaryl (1-naphtyl-N-methylcarbamate) in aqueous solutions containing suspended TiO2 (anatase) particles, under irradiation with simulated AM1 solar light, was investigated. A neat inhibitory effect on the degradation rate was observed, depending on the nature of the surfactant and on the initial pH of the solution. The decay profiles of the primary process corresponded to the usual pseudo-first order kinetics for surfactant concentrations below the critical micellar concentration range, whereas a more complicate behaviour was observed in the presence of micellar aggregates. Mineralization of the p…

Photon absorption by aqueous TiO2 dispersion contained in a stirred photoreactor

1991

We present a simple experimental method which allows the evaluation of the absorbed photon flow. The method is based on measurements of transmitted photon rates (by means of standard actinometer solutions) for different reactor thicknesses and/or catalyst concentrations. The method was applied to phenol degradation reaction carried out in a stirred batch phtotoreactor containing aqueous TiO 2 (anatase) dispersion, directly irradied by a 1,500 W Xe lamp

The influence of the anatase nanoparticles boundaries on the titania activity performance

2014

Metal oxides structures, formed by ordered self-assembling of crystalline nanoparticles aggregates, are attracting growing attention in fields such as catalysis or solar cells. The properties of these structures are influenced not only by their morphology and nanoparticles composition but also by the assembled particles boundaries. In order to determine the influence of these boundaries on the structures properties, the present investigation has been devoted to study the characteristics of anatase nanoparticles boundaries in titania aggregates prepared by TiCl4 hydrolysis at low temperature. Proton magic angle spinning nuclear magnetic resonance and high resolution transmission electron mic…

TiO2 photocatalysts prepared by thermohydrolysis of TiCl4 in aqueous solutions

2010

Abstract Nanostructured TiO 2 photocatalysts were synthesized by thermohydrolysis of TiCl 4 at 100 °C in various aqueous solutions. Anatase or rutile, binary mixtures of anatase and rutile or anatase and brookite, and ternary mixtures of anatase, brookite and rutile were obtained depending on the hydrolysis solution. The most efficient catalysts consisted of ternary mixtures of the three polymorphic TiO 2 phases.

Mesocrystalline Cr and Sb-codoped anatase visible-light-driven photocatalyst

2018

Abstract We report on the synthesis, characterization and visible-light-driven photocatalytic activity of mesocrystalline Cr- and Sb-codoped anatase nanoparticles. Discrete and morphologically well-defined assemblies of anatase nanoparticles sized below 100 nm × 50 nm were prepared by hydrothermal aging of aqueous solutions containing titanium alkoxide, chromium acetylacetonate, antimony acetate and triethanolamine (TEOA) as stabilizer. The as-prepared and TEOA-free doped nanoparticles showed similar crystallographic parameters and spectroscopic features. The incorporation of Cr and Sb dopant cations into the anatase nanoparticles was evaluated by Rietveld refinement of X-ray diffraction pa…