M. Macías

Influence of residual carbon on the photocatalytic activity of TiO2/C samples for phenol oxidation

TiO2 nanoparticles have been prepared by a novel alkoxide sol–gel precipitation. The presence of active carbon in different percentages could act as an interesting template. Upon calcination, carbon is eliminated leaving surface features significantly different from TiO2 prepared in the absence of carbon. Influence of calcination temperature and times will be studied. Detailed surface and structural characterisation of samples have been carried out. The correlations between residual carbon percentage after thermal treatment and photoactivity during phenol oxidation are reported.

The Diet of the Glossy Ibis During the Breeding Season in Doñana, Southwest Spain

Abstract We present the first detailed study of the diet of Glossy Ibis (Plegadis falcinellus) in Europe, from an expanding breeding colony in Doñana, southwest Spain. In 2000, fecal samples, mainly from adults, were collected from 15 nests. In 2001, 36 regurgitates were collected, mainly from large chicks. Fecal contents were dominated by aquatic beetles (Coleoptera) and dragonfly (Odonata) larvae, which were present in 100% and 93% of samples respectively. Regurgitates contained mainly aquatic beetles (41% by aggregate percent, mainly Cybister spp.), dragonfly larvae (29%, mainly Sympetrum fonscolombei, Aeshna mixta and Anax imperator), Sharp-ribbed Salamanders (Pleurodeles waltl, 12%) and Carp (Cyprinus carpio, 7%). The absence of vertebrate and other hard remains from feces was presumably due to their excretion in pellets. Thus fecal analysis is not a suitable method to investigate the food of the Glossy Ibis. The results suggest that there may be no major difference in the diet of breeding adults and their chicks, and that the recent increase in numbers of this ibis in Doñana is not explained by the abundance of introduced Red-swamp Crayfish (Procambarus clarkii) in the breeding area.

Preparation and Characterization of Amorphous ZrO2-SiO2 Composite Powders Processed by Sol-Gel Chemistry

Composite ZrO2-SiO2 powders, with different ZrO2 contents, including pure ZrO2 powders, were prepared by precipitation in SiO2 suspensions, of zirconia gels from solutions of zirconyl chloride at pH = 11. These products were investigated in connection with the phase changes in ZrO2 caused by heat-treatments. ZrO2-SiO2 mixtures containing 0–100% mol ZrO2, were studied by differential thermal analysis (DTA), X-ray powder diffraction (XRD), temperature programmed desorption combined with mass spectroscopy (TPD-MS), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX), to obtain information on the morphological and structural features of the particles before and during the heat treatment up to 1200°C. Specific surface areas were determined using nitrogen adsorption by the BET method. The results offer an explanation about some of the factors which can be influencing on the stabilization of metastable-cubic/tetragonal (C/T) phase of ZrO2 and the evolution of surface areas (“vulcano” profile) observed in the composites.

XAFS study of TiO2/SiO2 system prepared by sol–gel from inorganic precursors

Abstract The samples of 5%TiO 2 /SiO 2 prepared by sol–gel method from inorganic precursors calcinated at the various temperatures were studied by XAFS spectroscopy at Siberian Synchrotron Radiation Center. It was established that structural lability of this system and the change of symmetry of the oxygen coordination around the Ti(+4) ions depends on the calcination temperature. It seems that the mechanism of dissolution of the Ti(4+) ions in SiO 2 depends on the calcination temperature and consists in the formation of Wadsley defects following the incorporation of SiO 2 in TiO 2 particles.

Degradation of n-Butyl tin Chlorides in Waters. A Comparative Assessment of the Process by Photo-assisted and Chemical- treatment Methods

Abstract The degradation of aqueous n-butyl tin by several selected advanced oxidation technologies (AOTs) was studied and comparisons made between the processes. UV-photolytic and TiO2-photoassisted oxidation and treatment with chemical oxidants (hydrogen peroxide, hypochlorite) were thus evaluated in terms of their action upon n-butyltin chlorides in water.

Degradation of Phenylmercury Compounds by Heterogeneous Photocatalysis Over α-Fe2O3

Abstract We report here on the degradation of diphenylmercury and monophenylmercury chloride in air-equilibrated aqueous solutions by heterogeneous photocatalysis over α-Fe2O3. Photocatalysis proceeded via sequential de-phenylation leaving inorganic mercury. GC-MS analysis of the products revealed that photocatalytic degradation involved hydroxylation of the phenyl rings. Mechanistic features and photocatalytic activity were also studied and are reported upon.