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[EN] In this study, the photocatalytic activity in hydrogen production of a TiO catalyst with hierarchical structure and microsphere morphology was tested. This catalyst was synthesised by hydrolysis and condensation processes from a Ti(OBut) precursor and calcined at 150 °C, 400 °C and 630 °C. Hydrogen production of the subsequent photocatalysts rose by two and three orders of magnitude after the incorporation of Au or Pt particles by photodeposition. The microspheres with and without metal modification were characterised by scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD), Raman, Brunauer–Emmett–Teller (BET) surface area, Fourier transform infrared spectroscopy (FTIR) and diffuse reflectance measurements. The highest production rates were obtained for the metal-modified photocatalysts calcined at 400 °C. Hydrogen production increased with Au loading, attaining a rate of 1118 μmol·h for the 1.5 wt% Au photocatalyst. However, the highest production rate in the case of Pt was attained with just 0.27 wt% and was almost twice as high as that obtained with Au, 2125 μmol·h. When compared with previous studies by our team under the same conditions, this high production rate, obtained with a very low Pt loading, was only exceeded by the reference Aeroxide P25 TiO catalyst with a Pt loading greater than 1.5 wt%., This work was supported by the Spanish Ministry of Science and Innovation through the project IPT-120000-2010-033(GESHTOS). We would also like to thank the Spanish Ministry of Science and Innovation for the UNLP10-3E-726 infra-structure, co-financed with ERDF funds. T. Jardiel alsoacknowledges the financial support of the MAT2014-59210-JIN project of MINECO. M. Nereida Suárez would also like to thankthe University of Las Palmas de Gran Canaria for its fundingthough the PhD Grant Program.

Two series of new photocatalysts were synthesized based on modification with Pd of the commercial P25 photocatalyst (EVONIK&reg, ). Two techniques were employed to incorporate Pd nanoparticles on the P25 surface: photodeposition (series Pd-P) and impregnation (series Pd-I). Both series were characterized in depth using a variety of instrumental techniques: BET, DRS, XRD, XPS, TEM, FTIR and FESEM. The modified series exhibited a significant change in pore size distribution, but no differences compared to the original P25 with respect to crystalline phase ratio or particle size were observed. The Pd0 oxidation state was predominant in the Pd-P series, while the presence of the Pd2+ oxidation state was additionally observed in the Pd-I series. The photoactivity tests were performed in a continuous photoreactor with the photocatalysts deposited, by dip-coating, on borosilicate glass plates. A total of 500 ppb of NO was used as input flow at a volumetric flow rate of 1.2 L&middot, min&minus, 1, and different relative humidities from 0 to 65% were tested. The results obtained show that under UV-vis or Vis radiation, the presence of Pd nanoparticles favors NO removal independently of the Pd incorporation method employed and independently of the tested relative humidity conditions. This improvement seems to be related to the different interaction of the water with the surface of the photocatalysts in the presence or absence of Pd. It was found in the catalyst without Pd that disproportionation of NO2 is favored through its reaction with water, with faster surface saturation. In contrast, in the catalysts with Pd, disproportionation took place through nitro-chelates and adsorbed NO2 formed from the photocatalytic oxidation of the NO. This different mechanism explains the greater efficiency in NOx removal in the catalysts with Pd. Comparing the two series of catalysts with Pd, Pd-P and Pd-I, greater activity of the Pd-P series was observed under both UV-vis and Vis radiation. It was shown that the Pd0 oxidation state is responsible for this greater activity as the Pd-I series improves its activity in successive cycles due to a reduction in Pd2+ species during the photoactivity tests.

The copper-impregnated pyrophyllite (Cu/RC) was prepared and used as catalyst in catalytic wet peroxide oxidation (CWPO) of phenol. The catalyst was prepared by impregnation of copper (2.5 wt%) into pyrophyllite-type clay and characterized by X-ray diffraction, X-ray fluorescence, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. The optimum operation conditions for CWPO of phenol over Cu/RC were determined by investigating the effects of pH, temperature, catalyst amount, and hydrogen peroxide concentration. Stability of the Cu/RC catalyst and toxicity of treated solution were studied, by measuring the copper concentration leached out from the catalyst and the inhibition of Vibrio fischeri bacteria bioluminescence, respectively. The probable degradation mechanism of phenol over Cu/RC was considered by HPLC analysis. The obtained results showed that Cu/RC achieved highest activity (total phenol degradation and 80% TOC reduction) and detoxification with remarkable low copper leaching concentration (0.006 $$\hbox {mg\,L}^{-1})$$ at optimized conditions (pH $$=$$ 3, $$T = 50\,{^{\circ }}$$ C, 2 $$\hbox {g\,L}^{-1}$$ catalyst amount, 50 mg $$\hbox {L}^{-1}$$ phenol concentration and 7.45 $$\hbox {mmol\,L}^{-1}$$ hydrogen peroxide concentration during 4 h). Meanwhile, few intermediates with low concentration were observed by the HPLC analysis for the CWPO of phenol. The Cu/RC catalyst showed a good activity after five successive runs (88% of degradation and 73% mineralization) at optimized conditions.

In this work, novel TiO2-based nanobelts with various phases were synthesized: biphasic TiO2(B)/anatase, pure TiO2(B) and pure anatase. These catalysts were obtained via hydrothermal reaction using two nanoparticulated TiO2 photocatalysts as precursors: Aeroxide TiO2 P25 (P25) and TiO2 synthesized via a sol-gel process (SG). In addition, the surface of the photocatalysts was modified with gold using a photodeposition method. A characterization study of the different photocatalysts was performed with X-ray diffraction analysis (XRD), UV–Vis diffuse reflectance spectra (DRS), scanning electron microscopy (SEM), X-ray photoelectron spectrum analysis (XPS) and Brunauer-Emmett-Teller measurements (BET). The photocatalytic reaction of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) was investigated under UVA irradiation. A toxicity analysis was performed with the marine bioluminescent bacteria Vibrio fischeri. The highest 2,4-D removal efficiency of 99.2% was obtained with the biphasic Au-TiO2(TiO2(B)/anatase) nanobelts with anatase as predominant phase. Toxicity was mainly due to the intermediate 2,4-dichlorophenol (2,4-DCP) which was eliminated in 4 h. The TiO2 nanobelt phase structure is shown to have a significant effect on photocatalytic activity.

$$\hbox {TiO}_{2}$$ was obtained by a simple sol–gel synthesis and subsequently modified by the addition of Pt and/or Pd particles on the surface by photodeposition. These photocatalysts were characterised by X-ray diffraction analysis, UV–Vis diffuse reflectance spectra, Brunauer–Emmett–Teller measurements, Fourier transform infrared spectroscopy, transmission electron microscopy, electron dispersive spectroscopy and X-ray photoelectron spectroscopy. Their photocatalytic activity was studied by following the degradation, mineralisation and detoxification of solutions of phenol, propanil and methylene blue. For comparison purposes, different commercial $$\hbox {TiO}_{2}$$ catalysts were also tested: Kronos vlp7000, Millenium PC100, Aeroxide P90 and Aeroxide P25. This latter catalyst was also modified with Pt and/or Pd. The degradation kinetics of all the pollutants in aqueous solutions satisfactorily followed the pseudo-first order according to the Langmuir–Hinshelwood model in conditions of low concentration values. It was found that the simultaneous photodeposition of Pt and Pd contributed to enhancing photoactivity more than the individual deposition of either Pt or Pd.

This work analyses the treatment of ornamental aquaculture wastewater contaminated with the antibiotic metronidazole (MTZ) using a reactor with supported TiO 2 . Preliminary photolysis and hydrolysis studies revealed inefficient elimination of this pollutant under the study conditions. The activity of various photocatalysts in suspension in the elimination of 40 mg·L −1 of MTZ was studied, as well as the degradation performance in different aqueous matrices using UV-A radiation. Process efficiency was strongly and negatively affected by the presence of ions in solution, with a 20% decrease in mineralization. The highest reaction rates was observed with the Evonik-P90 (0.0625 min −1 ) versus Hombikat (0.0078 min −1 ). A number of configurations were evaluated to optimise the performance of the reactor with immobilized catalyst in MTZ degradation. Different types of illumination (UV-A and UV-C) were tested as well as the positions of both lamp and catalyst inside the reactor. Various configurations were able to completely eliminate 10 mg·L −1 of MTZ. A greater efficiency was observed in general in the degradation processes with the catalyst immobilized on the outer tube with the internal UV-C lamp (k E.UVC ; 0.042 min −1 ), compared UV-A lamp (k E.UVA ; 0.022 min −1 ). The best configuration was catalyst immobilized on the outer with the internal UV-C lamp and hydrogen peroxide (k E.UVC* ; 0.055 min −1 ).The deposited catalyst was also successfully subjected to continuous re-runs using the optimised configuration with no catalyst deactivation observed. Despite a decrease in photocatalytic activity of 24% after the sixth re-run, 100% MTZ elimination was still achieved. The degradation pathway of metronidazole using TiO 2 photocatalysis has also been proposed and detoxification of the samples after the photocatalytic treatment was evaluated using V. fischeri bacteria test.

La presente investigación tiene como objetivo analizar la influencia del aprendizaje basado en tareas en el desarrollo de la producción oral del idioma francés nivel B1. Se plantearon la hipótesis alterna y la hipótesis nula. Se realizó una profunda investigación teórica de las dos variables. La metodología se enfocó hacia la investigación cuanti-cualitativa y el nivel planteado se orientó a la investigación explicativa cuyo nivel se basó en la investigación cuasi experimental estableciendo el grupo de experimental y control a los que se aplicó dos instrumentos el pre test y el post test. Los datos obtenidos, sirvieron para obtener el cálculo de la media aritmética y la desviación típica. Posteriormente se hizo la prueba Z y se determinó la aceptación de la hipótesis alterna. Para la variable independiente se aplicó la técnica de la entrevista al área de francés de la Carrera Plurilingüe cuyos resultados corroboraron al aporte significativo de método del aprendizaje basado en tareas en la producción oral de los/las estudiantes del quinto semestre.

A study is undertaken of the effect of fluorinating two TiO catalysts, both with the same surface area but one composed only of pure anatase phase (SA) and the other of mixed anatase and rutile phases (P25), on the degradation of phenol, formic acid and aniline. The catalysts were characterised by FTIR, BET, EDAXs, SEM, XRD and DRS-UV–vis studies. The method used for synthesis of the F-P25 and F-SA resulted in fluorinated catalysts with properties different to those of other fluorinated catalysts reported in the bibliography. The results obtained show that, unlike other studies in which the formation of free hydroxyl radicals ([rad]OH) was enhanced with the fluorinated catalysts, in the F-P25 and F-SA catalysts it was the formation of surface hydroxyl radicals ([rad]OH) which was significantly enhanced. In this way, the F-P25 and F-SA catalysts gave rise to higher degradation rate constants of phenol (k), aniline (k) and formic acid (k) than the P25 and SA catalysts., We are grateful for the financial support of the Spanish Ministry of Economy and Competitiveness through the projects CTQ2015-64664-C2-1-P and the Spanish Ministry of Science and Innovation for the UNLP10-3E-726 infrastructure, co-financed with ERDF funds. D. Garzón Sousa would like to thank the University of La Palmas de Gran Canaria for its funding through its PhD Grant Program and Wiâm El-Alami would also like to thank the UNetBA Erasmus Program for its funding through a mobility grant.

El presente trabajo investigativo tiene como propósito principal comprobar si existe la aplicación de estrategias metacognitivas para el desarrollo de la comprensión auditiva del inglés. Como primer aspecto relevante se evidencia la literatura científica sobre el tema, posterior a esto se elaboró tres instrumentos para la recolección de datos. Se realizó la encuesta a los docentes del área de inglés con el propósito de medir su nivel de conocimiento sobre metacognición y las estratégias metacognitivas. De igual manera, se construyó una prueba de comprensión auditiva y se aplicó el cuestionario que mide la consciencia metacognitiva sobre la habilidad de escuchar en inglés (MALQ). El análisis e interpretación de los datos proyectó que los docentes tienen un buen nivel de conocimiento sobre metacognición, sin embargo no aplican metacognición durante sus clases en una actividad auditiva. Esto es comprobable con los datos que demuestran tanto la prueba de comprensión auditiva como los resultados del cuestionario metacognitivo que señalan que una gran mayoría de estudiantes no conoce sobre estrategias metacognitivas para mejorar la comprensión auditiva del inglés. En consecuencia se plantea una guía estratégica para promover el desarrollo de dichas estrategias en los estudiantes y su aplicación por parte de los docentes.

TiO2 deactivation processes during gas-phase degradation of ethanol were studied. To force the deactivation processes, various cycles were performed, avoiding the degradation of acetates. It was observed that acetates adsorbed on the anatase phase of catalysts provoke the transference of electrons to surface traps which modify the electron states of the semiconductor. The same deactivation studies were also performed with fluorinated TiO2. It was noted that the electrons present in the surface traps, as a consequence of the Ti-F interaction, react with the holes during irradiation and provoke a change in the electron states of the semiconductor.

A detailed study is undertaken of the photocatalytic activity in hydrogen production of the commercial photocatalyst Kronos vlp7000 (KR) surface-modified with photodeposited platinum particles (2.1 wt% Pt). The influence of different photocatalytic variables is studied: photocatalyst loading, suspension pH value and the nature and concentration of the sacrificial agent used. Optimum pH was found to be neutral or slightly acidic. The catalyst loading, which ranged between 0.5 and 2 g L −1 , had little effect on hydrogen production. In general, the results for the tested sacrificial agents in terms of hydrogen production were as follows (in descending order):methanol > ethanol > ethylene glycol > glycerol. In studies of reuse the commercial photocatalyst Kronos shows better perform in its photoactivity than the commercial photocatalyst Aeroxide TiO 2 P25. Finally, studies were also undertaken of photoactivity under solar radiation in which promising results were obtained (5.5–18 mL h −1 ).

Differences in the gas-phase photocatalytic degradation of NH3 and ethanol in the presence of water over two commercial TiO2 materials with different structural characteristics (Evonik's P25 (P25) and Sigma Aldrich's anatase (SA)) were established here using FTIR. The materials were characterized using different techniques including BET, XRD, UV–vis DRS and XPS. The interaction of CO probe molecule with the oxides was evaluated via calorimetry and by in-situ DRIFTS coupled to on-line mass spectrometry. This allowed us to determine differences in the surface properties of the two TiO2 materials. NOx− surface species became evident during the photodegradation of adsorbed NH3 over both SA and P25. However, while surface bidentate nitrate species remained strongly bound to P25, the surface species were fully eliminated from SA. Differences in the photocatalytic degradation of ethanol over P25 and SA were also determined. Ethanol adsorption and its evolution were largely independent of the presence of oxygen for SA, but oxygen affected these processes for P25.

The aim of this study was to find a recycling use for waste material (WTiO) that results from the extraction process of TiO from ilmenite in the pigment industry. In view of its high TiO content, the photocatalytic activity of this material was tested in the degradation of humic and fulvic acid substances (HFAs) and showed low levels of photoactivity, as was the case for the commercial photocatalyst Aeroxide TiO P25 (P25). However, due to its high Fe content, an important application was observed for WTiO as an HFA coagulant and catalyst in Fenton and photo-Fenton processes. A two-stage process of coagulation and photo-Fenton treatment was subsequently designed and conducted at laboratory and small pilot scale. High percentages (above 95%) were obtained in total organic carbon (TOC) removal., The authors acknowledge the financial support for this research from the Spanish Ministry of Science and Innovation (MICINN) under the project FOXMORE (CTM2006-05114) and from the Spanish Ministry of Economy and Competitiveness under the Infrastructure Project UNLP10-3E-726, co-financed with ERDF funds. E. Pulido Melián would also like to thank the University of Las Palmas de Gran Canaria for her postdoctoral contract.

In this work, a TiO 2 photocatalyst synthesized using a sol–gel procedure (SG750) was Pt modified through photodeposition (SG750-2.1 wt%Pt) and tested for its efficiency in hydrogen production by heterogeneous photocatalysis in the presence of different alcohols as sacrificial agents. The tested alcohols were: methanol, ethanol, ethyleneglycol and glycerol. Production was continuously followed for 3.5 h. The concentration of each alcohol that resulted in the highest production was optimized and some of the degradation intermediates were identified and quantified in both gaseous and the remaining liquid phase at the end of the process. Optimum concentrations were found to be around 17.13 M for methanol and 7.34 M for ethanol, ethyleneglycol and glycerol. In terms of sacrificial agent used, hydrogen production was as follows: methanol > ethanol > ethyleneglycol > glycerol. The stability of the photoactivity of the catalyst was demonstrated through reuse cycles with 0.011 M of sacrificial agent and was also compared with that of commercial photocatalysts, in this case Aeroxide TiO 2 P25 and Hombikat UV-100, with the same photodeposited Pt%.

This work studies the elimination, mineralization and detoxification through Fenton-based processes of wastewaters contaminated with the fungicide imazalil as a result of the postharvest treatment of bananas. Fe(II) and H2O2 concentrations were optimized for degradation of the corresponding imazalil concentrations. The activity of the imazalil degradation process was studied in deionized water and in simulated and real agro-industrial wastewaters. Results show that the water matrix had no detrimental effect on wastewater treatment when using the Fenton technique, but optimal iron content had to be increased when applying the photo-Fenton process. Even so, the optimal iron and H2O2 contents required for the photo-Fenton reaction were 6 times and 50% lower, respectively, than for the Fenton procedure. Solar pilot plant tests confirmed the detoxification of two agro-industrial wastewater effluents containing imazalil.

In this study, the photoactivity of commercial and lab-made TiO2 when immobilized on different supports, namely borosilicate glass, alumina foam and refractory brick, was examined for the removal of the fungicide imazalil from different water matrices. Alumina foam provided the largest exposed photocatalyst surface but degradation kinetics were not significantly improved by the use of this material. TiO2 coatings were also subjected to thermal treatment at 450 °C to improve adhesion to the support and exhibited higher photocatalytic mineralization, at levels comparable to the conventional suspended system. However, successive photocatalyst reuse led to its deactivation. Different regeneration methods were studied for the TiO2 films and it was concluded that deionized water washes were the most effective regeneration procedure. Finally, a typical industrial wastewater containing imazalil was successfully treated using TiO2 supported on borosilicate glass under solar irradiation.

The detoxification process of waters contaminated with phenol, formaldehyde and phenol–formaldehyde mixtures was studied using advanced oxidation treatments (heterogeneous photocatalysis and Fenton), biological techniques (aerated biological and wetland reactors) and combinations of the two. It is shown that photocatalysis was efficient in the detoxification of concentrations below 50 mg L −1 of those compounds. Sample toxicity increased at higher concentrations due to the generated intermediates. Phenol–formaldehyde mixtures were impossible to detoxify by heterogeneous photocatalysis at any of the studied concentrations. Treatments using the Fenton reaction were able to degrade concentrations above 1000 mg L −1 , though the use of a reagent such as peroxide makes it a costly technique. The efficiency of the biological aerated filter (BAF) mainly depended on initial concentration and toxicity, with removal rates of 3.08 and 0.26 g L −1 d −1 obtained for phenol and formaldehyde, respectively. Taking into account the results obtained for the treatment of complex phenol–formaldehyde mixtures, the best combination of techniques for the treatment of concentrations found in the industrial wastewater studied in this paper was the Fenton + BAF technique which was able to detoxify phenol–formaldehyde concentrations (1:1) of 1000 mg L −1 .

In this study, a comparative analysis is made of TiO modified with Pt or Au in NO photoxidation under different radiation and humidity conditions. The metals were deposited on the TiO surface using two methods, photodeposition and chemical reduction. All catalysts were supported on borosilicate 3.3 plates using a dip-coating technique. These modified photocatalysts were characterized by X-ray diffraction analysis (XRD), UV–vis diffuse reflectance spectra (DRS), Brunauer-Emmett-Teller measurements (BET), transmission electron microscopy (TEM) and X-ray photoelectron spectrum analysis (XPS). It was found from the XPS results that Pt and oxidized Pt species coexist on the samples obtained by photodeposition and chemical reduction. In the case of Au, though other oxidation states were also detected the dominant oxidation state for both catalysts is Au. TEM results showed most Au-C particles are below 5 nm, whereas for Au-P the nanoparticles are slightly bigger. With UV irradiation, the Pt modified catalysts do not show any significant improvement in NO photocatalytic oxidation in comparison with the unmodified P25. For Au, both modified photocatalysts (Au-P and Au-C) exceed the photocatalytic efficiency of the unmodified P25, with Au-C giving slightly better results. The incorporation of metals on the TiO increases its activity in the visible region., We are grateful for the financial support of the Spanish Ministry of Economy and Competitiveness through the project IPT-2012-0927-420000 (HORMIFOT) and thank the Spanish Ministry of Science and Innovation for the UNLP10-3E-726 infrastructure co-financed with ERDF funds. Part of this work was supported by research funding from Project Ref. CTQ2015-64664-C2-2-P (MINECO/FEDER, EU). XPS and other research services of SITIUS University of Seville are also acknowledged. M.J. Hernández Rodríguez and E. Pulido Melián would also like to thank the University of Las Palmas de Gran Canaria for, respectively, their research training grant and postdoctoral contract.

An optimization study was carried out from the detoxification of waters contaminated by the herbicide propanil at the maximum concentrations found in different rice-growing cooperatives in Ecuador. Studies included the degradation, mineralization and detoxification of the herbicide through TiO 2 -photocatalysis using two different catalysts, P25 Evonik and ECT1023t (a catalyst prepared by our research group), and through the Fenton reaction. It was determined that pH (studied between 3 and 7) had a determining effect on mineralization, especially with P25, but not on degradation. Adsorption and FTIR studies revealed a strong interaction of propanil with the catalyst surface, which conditioned the effectiveness of each of the studied catalysts. Propanil degradation with TiO 2 -photocatalysis occurred in 2 h, but complete detoxification required 12 h. In the case of the Fenton reaction, degradation was immediate but detoxification was not possible due to the inhibition of mineralization. With these results in mind, a study was made of a combination of the Fenton and TiO 2 -photocatalysis methods using ECT1023t, which resulted in a fourfold increase in the detoxification rate compared to that for heterogeneous photocatalysis. This result may be highly significant for the application of these techniques in processes in which the reaction time is of considerable importance.

In this work we studied the elimination, mineralization and detoxification of wastewaters from banana postharvest industries, contaminated with the fungicide imazalil, by means of heterogeneous advanced oxidation processes. We compared the activity of the commercial photocatalyst Evonik P25 and the lab-made EST-1023t in the degradation of imazalil in deionized water and in industrial wastewater. Results show an important negative water-matrix effect for wastewater treatment at acidic pH values due, mainly, to the presence of ions adsorbed onto the TiO 2 photocatalyst surface. At pH 7 only bicarbonate anions and bacteria hindered the degradation and mineralization of imazalil. Mineralization of imazalil was completely inhibited by dissolved aluminium in concentrations as low as 5 mg L −1 .

Sol–gel synthesised TiO2 developed by our group was modified through the addition of nickel nitrate and ammonium carbonate in the synthesis process. Photocatalysts were synthesised with different Ni/Ti molar ratios (0.015, 0.030, 0.045) and constant Ni/N ratio equal to 1.5 and subjected to post-calcination at temperatures of between 400 °C and 700 °C. Characterisation was carried out with: X-ray diffraction (XRD), UV–vis diffusive reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy-energy dispersive X-ray analysis (TEM-EDX), thermal analysis (TGA, DTA), aggregate size distribution, Fourier transform infrared spectroscopy (FTIR) and nitrogen adsorption-desorption isotherm (BET). Photoactivity in terms of photocatalytic hydrogen production was tested using a suspension of photocatalyst at 25 vol.% methanol. With a continuous flow of N2 in headspace the hydrogen produced was conducted to a gas chromatograph for quantification. No evidence of the presence of N was found in the photocatalyst. However, the presence of Ni enhanced TiO2 photoactivity, with a calcination temperature of 550 °C resulting in the highest photoactivity value of 260.76 μmol h−1.

Three activated carbons were produced by means of phosphoric acid impregnation from Phoenix canariensis palm frond mulch at three temperatures (450, 550 and 650 °C). The starting material, the resulting activated carbons and a commercial high performance activated carbon (Darco KB-G, Norit) were subjected to different techniques to determine their characteristics. The starting material without impregnation, carbonization and activation (as a biosorbent) and the activated carbons were applied to the removal of the fungicide Imazalil (sulphate formulation). The effects of initial concentration, initial pH and temperature on the kinetic parameters were studied for the activated carbons. Only the influence of initial pH was evaluated for the biosorbent. The kinetic experimental data were studied for their fit to pseudo-first and pseudo-second order kinetic models, with the latter providing a better mathematical fit. The adsorption isotherms of Imazalil at 25 °C were obtained, and the experimental data were fitted to Langmuir, Freundlich and Dubinin–Radushkevich models. The Freundlich model provided the best mathematical fit for the activated carbons, and the Langmuir model for the biosorbent. The activated carbons that were obtained showed high specific surface areas (988–1305 m 2 g −1 ), substantial total pore volumes (0.59–0.88 cm 3 g −1 ), acidic nature and good performance in the adsorption of the fungicide, especially the adsorbent obtained at 550 °C (186.15 mg g −1 ). Use of the precursor as a biosorbent is not recommended due to its poor adsorption capacity for the fungicide tested (57.46 mg g −1 ) and lignin release at pH ⩾ 7.

H2 production from methanol/water photo-splitting was compared using various commercial photocatalysts (Evonik P25 (P25), Hombikat UV-100 (HB) and Kronos vlp7000 (KR)) and others synthesised with a sol–gel-hydrothermal (HT) process and a sol–gel method followed by calcination (SG400 and SG750). All photocatalysts had been surface modified with Au at different concentrations, from 0.2 to 6.0 wt.%, using the photodeposition method. A complete characterisation study of the different photocatalysts was performed (BET, XRD, TEM, SEM-EDX, FTIR, UV–vis Reflectance Diffuse Spectra and aggregate size). The experiments were conducted for 3.5 h using 1 g L−1 of photocatalyst with methanol (25 vol.%) as sacrificial agent. In addition to H2 generation, production of the main intermediates, formaldehyde and formic acid, and of CO2 was also evaluated. The commercial photocatalyst KR at 0.8 wt.% Au had the highest H2 production of all the photocatalysts studied with 1542.9 μmol h−1. Of the photocatalysts synthesised by our group, SG750 at Au loading of 2.0 wt.% gave the highest H2 production of 723.1 μmol h−1. The SG750 photocatalyst at Au loading of 2.0 wt.% also had the highest H2 production yield per unit of surface area at 45.5 μmol g h−1 m−2.

The decolourization and mineralization of simulated wastewaters from wool dyeing tanks were investigated by Fenton and photo-Fenton processes. Yellow, red and blue dyebaths with azo-type and anthraquinone dyes and additives were selected as colored effluents. Photo-Fenton reaction was much more efficient than the respective dark reaction under identical experimental conditions. The effect of H 2 O 2 and Fe(II) dosage and fractional or initial addition of these reagents on the photo-mineralization processes were studied and the optimal conditions found. Experiments at a pilot plant based on compound parabolic collectors (CPCs) confirmed that, under optimal conditions, 100% of color removal was obtained requiring low accumulated energy. No toxic effects on marine bacteria Vibrio fischeri were observed at the end of photo-Fenton treatment for all studied effluents. High concentrations of sodium acetate are used as additive in the wool dying process. HPLC and TOC analysis of the effluents after photo-Fenton process confirmed that the remaining organic carbon is due to the presence of acetates. The obtained results showed the feasibility of photo-Fenton process to achieve suitable water qualities for internal reuse.

A series of synthesised TiO 2 -based and commercial photocatalysts were modified by Pt photodeposition and a study made of their photocatalytic activity in hydrogen production. The modified commercial photocatalysts were Evonik P25, Kronos vlp7000 and Hombikat UV-100, and the other modified photocatalysts were synthesised by our group using sol–gel and sol–gel hydrothermal processes ( SG400 , SG750 and HT ). Pt weight percentages used in the study were 0.5, 1.0 and 2.1 wt.% (Pt/TiO 2 ). The photocatalysts were extensively characterised by X-ray diffraction (XRD), UV–vis diffuse reflectance, Brunauer–Emmett–Teller (BET) surface area measurement, transmission electron microscopy (TEM), scanning electron microscopy (SEM–EDX), Fourier transform infrared spectroscopy (FTIR) and laser light dispersion. Methanol (25% vol.) was used as sacrificial agent over the 8 h of the hydrogen production tests and measurements were taken of the final concentrations of formaldehyde and formic acid as well as initial and final TOC. Photoactivity of all photocatalysts increased in the presence of Pt. The most efficient of the synthesised photocatalysts was SG750 and of the commercial photocatalysts P25 . Maximum production of SG750 was 1846 μmol h −1 at 1.0 wt.% Pt and its production per surface unit was notably higher than that of P25 .

The elimination and mineralization of the fungicide imazalil and its by-products has been studied by means of heterogeneous photocatalysis. The activity of different photocatalysts, including the commercial TiO2 benchmark photocatalyst (Evonik P25) and several TiO2-based lab-made catalysts, is compared. The best results were achieved with the new lab-made photocatalyst synthesized by using sulphuric acid in the sol–gel process and calcined at a high temperature (EST-1023t). The apparent initial rate constant was up to 2 times faster for EST-1023t when compared to that obtained with Evonik P25. The effect of different operating parameters (pH, photocatalyst load and initial imazalil concentration) on the photocatalytic process were studied for these two photocatalysts and a degradation pathway was proposed considering data obtained from ion chromatography, LC–MS and FTIR studies. The formation of imidazole acetic acids was confirmed, as well as complete mineralization and release of stoichiometric nitrogen (as ammonium and nitrate) and chloride ions.

TiO2 particles were prepared by sol-gel method alone and by sol-gel method combined with hydrothermal treatment. The structural and photocatalytic properties of the two series of photocatalysts were compared. XRD studies revealed that rutilization was faster in the series of photocatalysts, which had been additionally subjected to a hydrothermal process (SG-HT). The hydrothermally treated photocatalysts also displayed a higher specific surface area than those which had only been synthesized using the sol-gel process (SG) and subjected to low calcination temperatures of up to 873 K, while this tendency was inverted at higher temperatures. In accordance with the above observation, the hydrothermally treated series of photocatalysts had a lower particle size than the SG series calcined immediately after the sol-gel process up to 873 K, with this relation being inverted for the highest two temperatures which were studied (973 K and 1023 K) and which saw the commencement of rutilization. Increases in average particle size were observed for both series, with a polyhedral morphology seen as calcination temperature rose. FTIR studies highlighted the presence of the band at 2351 cm(-1) in the SG-HT photocatalysts, characteristic of surface-adsorbed CO2. This was not seen in the SG or P25 photocatalysts. In terms of photoreactivity, the best photocatalyst in the SG-HT series was that calcined at 923 K and in the SG series at 1023 K (SG-1023). Comparing these two photocatalysts and the commercial P25 photocatalyst, SG-1023 was found to be the most photoactive in both the photodegradation and the mineralization of phenol.

The photocatalytic degradation of the commercial dye Lanaset Sun Yellow 180 was studied in the presence and absence of the different additives used in the dye's formulation. The experiments were performed with Degussa P25 as received and doped with Fe (Fe-TiO2) and a new catalyst synthesized by our research group (ECT-1023). The best efficiency was achieved with Fe-TiO2. With this catalyst, the formation of a photoactive complex was observed between the dye and Fe atoms of the catalyst surface that accelerated degradation. FTIR studies revealed that the complex was formed by interaction between the dye's carbonyl groups and the atoms of the metal. In mixtures of the dye containing citric acid or acetate, degradation was notably inhibited with the catalysts Fe-TiO2 and ECT-1023 because of the formation of carboxylates on their surface. This inhibitory effect was neutralized when all the additives were present in the solution. Toxicity analyses indicated that intermediates were not toxic. Thus, the photocatalytic methods seem to be optimal for the decolourization of wastewaters containing this dye.

2,4 -dichlorophenol (DCP) was decomposed in the presence of TiO 2 suspensions by illumination. The operating variables that were studied included initial DCP concentration, photocatalyst doses and initial pH. Mineralisation was slow at the optimum pH (12) for DCP degradation, with the optimum pH for both degradation and mineralisation being pH o 5. The kinetic patterns were fitted to a first order kinetic. Adsorption and rate constants were obtained by using the Langmuir–Hinshelwood model. The adsorption isotherm was fitted to the Freundlich model and the Langmuir model with high coefficients of correlation. The adsorption constant in darkness was lower than that obtained with the kinetic model. According to the FTIR results, DCP–TiO 2 interaction occurs as a result of the formation of a phenolate . Of the three oxidants tested – hydrogen peroxide, ozone and sodium peroxodisulphate – only H 2 O 2 resulted in enhancement of the photocatalytic process.

A comparative study of the photocatalytic activity of two different TiO 2 catalysts in solar photocatalytic oxidation, mineralization and detoxification of waters containing herbicides 2,4-dichlorophenoxyacetic acid (2,4-D), bentazon and toxic intermediates was performed in a pilot plant scale photoreactor. Commercial TiO 2 (Degussa P25) and TiO 2 synthesized by citrate sol–gel method (ECT-1023t) were selected as photocatalysts. The optimal basic operational parameters to eliminate these herbicides and toxic intermediates were established for both catalysts at laboratory scale. ECT-1023t showed better photocatalytic activity than the commercial Degussa P25 at solar pilot plant scale with both herbicides in real water at natural pH (6.8–7.8) without any additive. The toxicity of the treated solutions was evaluated using the Microtox test based on the inhibition of bioluminescence of the bacteria Vibrio fischeri . The toxic effect of the main intermediate of 2,4-D, the 2,4-dichlorophenol (2,4-DCP), was higher than the parental herbicide. Acute toxicity of 2,4-D and intermediates (2,4-DCP) was reduced during the photocatalytic treatment by using ECT-1023t as photocatalyst. Longer times were necessary to obtain similar results when using P25 as photocatalyst. No inhibitory growth effect of the herbicide bentazon and its photoproducts on Vibrio fischeri bacteria bioluminescence was observed for either photocatalyst in any of the irradiated samples collected at predetermined times using an initial concentration of 0.1325 mM of the herbicide.

A Ti–H2O2–phenol complex, not described until now, has been identified on the surface of Degussa P-25 and the new catalyst ECT-1023. This complex is considered to be responsible for the higher hydroquinone to catechol concentration ratio. It has been also shown that phenolates identified on the surface modify electrodonation that controls the generation of activating positions of the aromatic ring. The different strengths of the Lewis acid centres identified provide phenolates with different electrodonation ability. It has been observed that P-25 has Lewis acid centres with stronger acid character than those of ECT-1023. Thus, the mechanism of phenol degradation is affected by the formation of complexes with H2O2 and the distribution and strength of Lewis acid centres of the studied catalyst.

In this work we compared the photocatalytic activity of sol–gel synthesized nanocrystalline TiO2 material (ECT-1023t) and a commercial TiO2 (Degussa P25) in the elimination, mineralization and detoxification of waters contaminated by the herbicide bentazon and its toxic intermediates under UV light. Adsorption and kinetics studies were undertaken and the effect of adding two different co-oxidants (H2O2 and S 2 O 8 2 - ) was analyzed for both photocatalysts. The optimal basic operating parameters (pH, photocatalyst load, initial concentration of bentazon) to eliminate the herbicide and its toxic intermediates were established for both photocatalysts. The most efficient TiO2 for removal of bentazon and its toxic intermediates was ECT-1023t at pH = 7. The apparent initial rate constant of bentazon degradation was two times higher for ECT-1023t than for P25. A Langmuir–Hinshelwood kinetic model showed satisfactory bentazon degradation of up to 0.25 mM for P25 and up to 0.05 mM for ECT-1023t. From FTIR studies, it seems that the interaction of bentazon with both photocatalysts occurred through the SO2 group. The most efficient photocatalyst for detoxification of treated solution was ECT-1023t, using the marine bacteria Vibrio fischeri as the test organism. When using an initial bentazon concentration of 0.265 mM, the evolution of toxicity saw a 72% reduction in bioluminescence inhibition for ECT-1023t and only a 33% reduction for P25 after 2 h of irradiation. No inhibitory growth effect of the herbicide bentazon and its photoproducts was observed for either photocatalyst in any of the irradiated samples collected at predetermined times when Lemna minor was used as the test organism. In parallel, the three photoproducts formed in the earlier steps of bentazon degradation were identified by LC–MS and a comparison on the evolution of these compounds by using both photocatalysts was performed. The results showed that the intermediates formed by hydroxylation of aromatic ring are in highest concentration when ECT-1023t is used. On the contrary, the hydroxylation of isopropyl group in bentazon is the main pathway of bentazon photodegradation when P25 is used as catalyst.

En el presente articulo se propone la aproximacion no convencional de osciladores de anillo interconectados y acoplados como redes de distribucion de reloj para la sincronizacion de sistemas electronicos en un solo circuito integrado. Se presentan resultados de simulacion HSPICE de redes de reloj convencionales (globales) y no convencionales (locales) utilizando parametros tipicos de un proceso de fabricacion de circuitos integrados CMOS ( Complementary Metal-Oxide Semiconductor ) de 0.35 µm pozo-N de Austria Micro Systems (AMS). Con base en resultados experimentales medidos en redes de distribucion de senal de reloj, locales y globales, fabricadas mediante el citado proceso, se muestra que la aproximacion propuesta es apropiada para sistemas en un solo circuito integrado, debido a su buen desempeno en frecuencia, consumo de potencia y alta robustez a variaciones del proceso de fabricacion. Ademas, las redes de osciladores de anillo interconectados y acoplados poseen modularidad, regularidad y tolerancia a fallas.

The degradation by Fenton and photo-Fenton of high concentrations of ethylene glycol (1000–25,000 mg/L), similar to those found in wastewater has been studied. Strongly exothermic reactions led to temperature increments up to 70–94 °C. In most experiments, temperature increments favored radical formation that provided almost complete mineralization. Oxalic, formic and acetic acids were identified as degradation intermediates. The obtained results indicate that the radicals formed in the degradation of formic and acetic acids with H2O2 were responsible for the exothermic reactions. Nonetheless, Fe–oxalic complexes inhibited the previous reactions by slowing down the process in such a way that complete mineralization did not occur until those complexes were degraded. FTIR studies allowed the identification of some of the complexes and species formed in the process.

TiO2 nanoparticles have been prepared by sol–gel precipitation and further hydrothermal treatment. In this way, the effect of the hydrothermal treatment on the structural properties and photocatalytic activity of sol–gel synthesized catalysts has been investigated. These catalysts have been produced by hydrolysis of a mixture of isopropanol–titanium tetraisopropoxide (iPrOH–TiiP). The prepared photocatalysts were characterized by means of X-ray diffraction (XRD), surface area analysis (BET), transmission microscopy (TEM), thermogravimetric analysis (TG), scanning electron microscopy (SEM) analysis, diffuse reflectance, sedimentability analysis and aggregate size study. Besides, the structural evolution with the temperature of the photocatalysts treated or not hydrothermally was studied. It was observed that the calcination produces approaching between the characteristics of both sets of photocatalysts. The photocatalytic activity of the obtained photocatalysts was investigated, using phenol as a model pollutant. The calcination temperature is the most remarkable factor that can affect the ultimate photocatalytic activity of the prepared photocatalysts. However, the hydrothermal treatment previous to calcination led to obtain photocatalysts which exhibit larger photocatalytic activity than their homologous photocatalysts without hydrothermal treatment. The obtained photocatalyst TiO2ht600 exhibits the same photocatalytic activity per surface area than the commercial TiO2 Degussa P25 but with much faster sedimentability.

The performance of two substrates commonly available in the zone, gravel and lapilli, was tested for their use in hybrid constructed wetland pilot plants for the treatment and reuse of urban wastewater in Gran Canaria, Canary Islands, Spain. The first stage of the systems was a vertical subsurface-flow constructed wetland and the second stage was a horizontal subsurface-flow constructed wetland. Parallel experiments were carried out with one system containing only crushed stone basaltic gravel as substrate and the other with only lapilli, a very porous volcanic sediment. The comparative effect of substrate type, hydraulic loading rate and planting was studied. Tracer studies indicated that the experimental TRHs were significantly lower than the theoretical ones, particularly for the vertical flow with gravel. Though the vertical flow with lapilli performed better than the one with gravel, the hybrids showed quite similar removals. Planting or varying the hydraulic loading rate introduced little differences between the vertical flows or the hybrids. Average removals for the gravel-based hybrid constructed wetland were 86% for BOD, 80% for COD, 88% for ammonia-N, 96% for SS and turbidity, 24% for phosphate-P, and 99.5% for faecal coliforms and 99.7% for faecal enterococci. Thus, it can be concluded that hybrid constructed wetlands proved to be robust configurations for wastewater treatment in the Canary Islands.

The effect of the mixing ZnO with different portions of activated carbon (AC) has been studied. The resulting catalysts were characterised and evaluated in the photocatalytic decomposition of aqueous pollutants. Changes in the catalyst colour and in the FTIR vibration bands of the surface hydroxyl groups were recorded. νOH vibrations were shifted to lower wavenumbers as AC loading increased, demonstrating modification of the acid-base character of the catalysts. Laser scattering studies showed that AC loading leads to smaller ZnO particles. BET surface area measurements and scanning electron micrograph (SEM) analysis showed agglomeration of ZnO particle pores in the AC structure. Results showed that in addition to a synergistic effect of the AC-ZnO combination, AC content modifies the ZnO particle properties and consequently photocatalytic behaviour. This was evident in phenol degradation experiments where changes in the concentration profiles of the catechol and hydroquinone degradation intermediates, were observed. However, the AC-ZnO catalysts were less efficient than pure ZnO in the degradation of 2,4-dichlorophenol (DCP). This seems to be due to the strong adsorption of the DCP molecule on AC, resulting in lower diffusion to the catalytic ZnO and thus a lower rate of photocatalysis.

Dissolved biochemical demand (BOD), total organic carbon (TOC) and NH4-N were analysed in seven sampling points in a pond–wetland system treating raw wastewater from 2001 to 2005 to determine the efficiency of its constructive elements. The wetland consists of horizontal flow stone filters, free water wetlands and a final subsurface flow wetland. Elimination (g d-1) and elimination efficiency (g d-1 m-2) were calculated for each constructive element. The highest BOD elimination was achieved by the pond (1714 g d-1), particularly when the highest BOD loads were applied. However, the highest BOD elimination efficiency was given by the first stone filter (45 g m-2 d-1). Although NH4-N elimination was highest in the pond and the horizontal subsurface flow constructed wetland with 432 and 104 g d-1, respectively, the stone filters achieved much higher elimination efficiencies than the other elements, about 15.8 g m-2 d-1 each. These results can be explained in terms of the combination of high bacterial activity in the stone filters with higher oxygenation in the pond and surface flow wetlands, and suggest that NH4-N elimination can be improved by combining short horizontal surface and subsurface flow wetlands instead of using only a longer subsurface flow constructed wetland.

Polychlorinated biphenyls (PCBs 28, 31, 52, 101, 138, 153, 180, and 209) were measured in tissue samples (liver and fat) from 30 loggerhead turtles Caretta caretta, 1 green turtle Chelonia mydas, and 1 leatherback Dermochelys coriacea stranded on the coasts of the Canary Islands, trying to establish a possible relation between PCB concentrations and the lesions and causes of death. Tissues from these turtles contained higher levels of PCBs than those reported in turtles from other geographical regions. Sigma PCB concentrations (1980+/-5320 ng g(-1)wet wt.) in the liver of loggerheads were higher than in the adipose tissue (450+/-1700 ng g(-1)wet wt.). Concentrations of PCB 209 in the liver (1200+/-3120 ng g(-1)wet wt.) of loggerheads and in the liver (530 ng g(-1)wet wt.) and adipose tissue (500 ng g(-1)wet wt.) of the leatherback were remarkable. Frequencies of detection of PCB 209 in the liver (15.5%) and adipose tissue (31%) were also remarkable. Cachexia was detected in 7 turtles (22%) and septicemia was diagnosed in 10 turtles (31%). Statistically, a positive correlation was detected between Sigma PCBs concentration and cachexia. Poor physical condition, cachexia and/or septicaemia could explain the high levels of PCBs and tissue distribution. However, no histological lesions exclusively attributed to the acute effects of PCBs were described. The most prevalent histological lesions were ulcerative and purulent oesophagitis, purulent dermatitis, necrotizing enteritis, and granulomatous pneumonia. The bacteria most frequently isolated were Escherichia coli, Staphylococcus sp., and Aeromonas sp. Although immunosupression as a result of PCBs pollution has been described previously, other factors in this study, such as incidental fishing, nutritional status, and exposition to different micro-organisms, make it difficult to establish a clear association between PCB concentrations and causes of death.

Formalin wastewater containing high concentrations of formaldehyde and TOC was treated and detoxified with biological aerated filter (BAF) and wetland reactors. At similar formaldehyde loading rates (about 0.01–0.9 kg/m3 d) both reactors provided high efficiencies but the BAF was more efficient at treating formaldehyde and TOC with average eliminations of 98 and 92%, respectively. However, the BAF effluent was not always detoxified according to the Lemna minor toxicity test as growth inhibition was above 20%. Although the elimination of formaldehyde and TOC achieved by the wetland reactors (81 and 25%, respectively) was lower than that of the BAF, they provided higher total nitrogen reduction. The combination of BAF and wetland reactors is proposed as a novel and convenient method for the treatment of formalin wastewater as it provided almost complete elimination of formaldehyde and detoxified samples with L. minor negative growth inhibition (−45 to −52%).

ZnO nanoparticles have been prepared by amine template assisted sol–gel precipitation and further hydrothermal treatment. We have investigated the effect of different pH values achieved by means of triethylamine (TEA) addition in the final surface and structural properties. Two sets of samples were obtained after thermal treatment, one with no hydrothermal pre-treatment and a second hydrothermally pre-treated. Surprisingly the precipitate obtained after the amine addition also exhibits good photocatalytic properties. It has been stated that calcination treatment leads in both sets of samples to a significant improvement in the photocatalytic properties of the studied systems. Therefore, interesting comparison has been performed between hydrothermal pre-treated and direct thermal treated samples. Surface and morphological features notably differ from ZnO prepared using different synthetic route. Wide surface and structural characterization of the samples have been carried out, and correlations with precipitation pH are pointed out from this characterization. In all cases, the amine templated ZnO obtained exhibit high conversion values for phenol photo-oxidation reaction. Further calcination treatment in all of the studied samples clearly leads to photocatalytic conversions higher than that exhibited by TiO2 Degussa P25. This fact is even more significant if we consider that hydrothermally and calcined ZnO exhibit almost null surface area values, leading to a startling intrinsic photoactivity. The structural excellence (crystallinity, lack of defects, crystallite size, etc.) of such systems is clearly responsible for their high photoactivity values. # 2008 Elsevier B.V. All rights reserved.

The photocatalytic techniques have been widely applied to the treatment of wastewaters. However, this work introduces an innovative application of photocatalysis to the treatment in continuous of gaseous contaminants. Packed reactors with different lengths and a spiral one have been designed to study the photocatalytic degradation of methyl tert-butyl ether (MTBE), individual alcohols and mixtures with their corresponding aldehydes. These studies have been performed with TiO2 (Degussa P-25) and TiO2 doped with Cu (Cu-TiO2). The results obtained have shown that these systems can degrade and mineralize the tested compounds, thus achieving the decontamination of their gaseous emissions. Additionally, the reactor with Cu-TiO2 has been more efficient than that with TiO2 at the degradation and mineralization of MTBE, being the photocatalytic behaviour of the former more easily altered by the presence of intermediates. Additionally, it has been observed that reactor morphology plays an important role in degradation efficiency. The spiral reactor with Cu-TiO2, in which the catalyst was thermally deposited on the inner walls, achieved the highest degradation and mineralization of MTBE. The obtained results are particularly interesting as an alternative to reduce emissions of volatile organic compounds to the atmosphere.

A comparison is made in this study of the effectiveness of various commercial catalysts in the oxidation of NO by heterogeneous photocatalysis. The following catalysts were considered: Aeroxide TiO P25, Aeroxide TiO P90, Hombikat UV-100, Kronos vlp7000, CristalACTIV PC105, CristalACTIV PC500, Kemira 650 and Anatasa Aldrich. All catalysts were deposited by a dip-coating technique onto borosilicate 3.3 glass plates. Optimization of catalyst load showed no significant enhancement of photoactivity, in general, above a deposited mass of 1.16 mg cm. Differences between photocatalyst activity were more apparent at longer illumination times. Photoactivity decreased in the presence of humidity and differences in the adsorbed products were detected. Photocatalyst activity was strongly influenced by specific surface area, with the best results obtained by the catalysts with the largest surface area, namely the PC500, Hombikat and Kronos. Photocatalyst stability was demonstrated in successive reuse cycles., We are grateful for the financial support of the Spanish Ministry of Economy and Competitiveness through the project IPT-2012-0927-420000 (HORMIFOT) and CTQ2011-24784 and thank the Spanish Ministry of Science and Innovation for the UNLP10-3E-726 infrastructure, co-financed with ERDF funds. M.J. Hernández Rodríguez and E. Pulido Melián would also like to thank the University of Las Palmas de Gran Canaria for their research training grant and postdoctoral contract, respectively.

This work studied the degradation and adsorption of dimethylphthalate (DMP) using various TiO-based photocatalysts: TiO Aeroxide P25, Kronos vlp7000, Hombikat UV-100, Kemira 650 and a synthesized photocatalyst named SG750. As the photocatalysts with mixed anatase and rutile phases, P25 and SG750, showed greater activity than those of pure phase, an in-depth study was undertaken of these two catalysts in the adsorption and degradation of DMP. The degradation results were fitted with a high degree of correlation to the Langmuir-Hinshelwood model and those for adsorption to the Freundlich model. The Freundlich constants showed good correlation with FTIR observations of the DMP-P25 and DMP-SG750 interactions. These two photocatalysts were additionally modified by photodeposition with Pt and Au (0.5–1.5 wt%) to study the effect of these metals on degradation and mineralization kinetics., E. Pulido Melián would like to thank the University of Las Palmas de Gran Canaria for her postdoctoral contract.

The kinetics and adsorption aspects of the photocatalytic degradation of three cresolic isomers were studied in aqueous suspension containing TiO 2 (Degussa P-25). The Langmuir–Hinshelwood model (L–H) was applied to the kinetic results. Degradation kinetic constants were similar for the three compounds ( o -cresol, 0.0188 ppm/s; m -cresol, 0.0166 ppm/s; p -cresol, 0.0182 ppm/s). However, the adsorption pattern of p -cresol is different from those of the other organics. Results from adsorption experiments carried out in darkness were modelized by using Langmuir and Freundlich isotherms. In general, the studied cresols showed little adsorption on TiO 2 surface. The adsorbed species on the catalyst surface were identified by FITR spectroscopy. According to these results, only p -cresol forms cresolates. An important correlation between Langmuir constants and FTIR results was observed.

The photocatalytic degradation of catechol, resorcinol, m-cresol, o-cresol and phenol has been studied individually, in dual mixtures and in the presence of hydrogen peroxide to determine possible competition for adsorption and photoactive centres and for the radicals photogenerated. The obtained results have shown that in the presence of hydrogen peroxide degradation rates are determined by the localization of specific adsorption centres more than by the amount of adsorbed molecules or the number of aromatic ring activating positions generated by substituents. The interaction of catechol with the hydroxyls responsible for the formation of the more photoactive OH radicals slows down the degradation of the other phenolics. Additionally, the interaction of each compound with the surface of TiO2 results in the change of the photoadsorption of oxygen. Consequently, degradation rates of the mixtures are also determined by the photoadsorption of oxygen.

With the goal of predicting the photocatalytic behaviour of different phenolic compounds (catechol, resorcinol, phenol, m-cresol and o-cresol), their adsorption and interaction types with the TiO2 Degussa P-25 surface were studied. Langmuir and Freundlich isotherms were applied in the adsorption studies. The obtained results indicated that catechol adsorption is much higher than those of the other phenolics and its interaction occurs preferentially through the formation of a catecholate monodentate. Resorcinol and the cresols interact by means of hydrogen bonds through the hydroxyl group, and their adsorption is much lower than that of catechol. Finally, phenol showed an intermediate behaviour, with a Langmuir adsorption constant, KL, much lower than that of catechol, but a similar interaction. The interaction of the selected molecules with the catalyst surface was evaluated by means of FTIR experiments, which allowed us to determine the probability of OH radical attack to the aromatic ring.

The photocatalytic mineralization of methanol, ethanol and 1-propanol is compared with those of their homologous carboxylic acids (formic, acetic and propanoic). The presence of S 2 O 8 2− ions almost does not affect the alcohols mineralization. But, those of the acids are slowed down. In addition to this, adding H 2 O 2 inhibits the alcohols mineralization and those of the acids, but to a lesser extent. FT-IR studies have shown that carboxylates generated from the oxidation of the corresponding alcohols adsorb at different centres from those where carboxylates directly generated from formic, acetic and propanoic acids do. From the obtained results, mineralizations of these compounds have been correlated with their proximity and accessibility to photoactive centres.