Efecto del escalamiento a 10 kg del catalizador Al/Fe-PILC sobre sus propiedades fisicoquímicas y catalíticas en la degradación de fenol

Durante la última década diferentes estudios han demostrado que las arcillas pilarizadas con el sistema mixto Al/Fe presentan una excelente respuesta catalítica en la degradación de compuestos orgánicos tóxicos disueltos en agua mediante Peroxidación Catalítica en Fase Húmeda (PCFH) [1-3]. Sin embargo,la implementación de ésta tecnología en la descontaminación de aguas a escala real depende fuertemente de la preparación reproducible del catalizador a mayor escala, sin una pérdida significativa de sus propiedades tanto fisicoquímicas como catalíticas. Este trabajo tiene como objetivo principal determinar el efecto de la preparación del catalizador Al/Fe-PILC en tres diferentes escalas y concentración de sus precursores

10 kg scaled-up preparation of Al/Fe-pillared clay CWPO catalysts from concentrated precursors

In this work, the significant intensification of a bentonite pillaring process was achieved by using a novel methodological approach, leading to an intercalating Al/Fe mixed oligomeric precursor, around 100 times more concentrated than usually reported. In addition, the intercalating step was achieved directly on the clay with no previous swelling of the mineral being required; this allowed the successful scaled-up preparation of the Al/Fe-PILC, by a factor of one thousand, from the lab (10 g) to the pilot scale (10 kg). Intercalating solutions prepared under either oncentrated (13 cm3) or diluted (widely reported, 2.0 dm3) conditions for lab-scale preparations were both translucent, displaying similar final pH values (close to 4.0) typical of highly oligomerized Al-pillaring solutions. The clay modified from concentrated precursors at the 10 g scale reached a high basal spacing (18.3 Å) and specific surface area (198 m2 g−1 ) with very comparable fractions of Fe forming truly mixed Al/Fe pillars in comparison to a reference material (H2-TPR analyses). This promoted high performance in the catalytic wet peroxide oxidation of phenol in aqueous solution as a toxic model organic molecule at very mild temperature (25.0 °C ± 1.0 °C) and pressure (76 kPa), exhibiting the highest catalytic efficiency as a function of both parameters (full conversion of phenol together with 45.2% of TOC mineralization) with low iron leaching using a very low catalyst concentration (0.25 g dm−3). Particle size refining of the starting clay, the speed of stirring and conditions for the final washing of the interlayered precursor are the main factors influencing successful pillaring at scales higher than 1.0 kg

Fenton-like oxidation of Orange II solutions using heterogeneous catalysts based on saponite clay

Fe-clay catalysts have been prepared and tested for Orange II oxidation with H2O2 in aqueous solution. Thereaction is carried out in a batch reactor, using different hydrogen peroxide concentrations, and in a wide range oftemperature and pH values. Twelve samples were prepared, with three different iron loads (7.5, 13.0 and 17.0 %,w/w), and using four iron salts as precursors, namely Fe(II) acetate, Fe(II) oxalate, Fe(II) acetylacetonate and Fe(III)acetylacetonate. The samples were characterized using X-ray diffraction, thermal analysis, infrared spectroscopy andadsorption of nitrogen at 77K. The catalytic results show that these solids present good catalytic properties for thedegradation and mineralization of Orange II solutions, allowing to reach, in the best conditions and after 4h ofoxidation, 99% of dye degradation with 91% of TOC (Total Organic Carbon) reduction (at 70ºC), using only ca. 90 mgof clay catalyst per litre of solution. Nevertheless, 96% of dye removal with 82% of mineralization were also reachedat 30ºC. Besides, the amount of iron released into the final solution is lower than 1 ppm, in the worst of the cases,and 0.09 ppm in the best case

Photodegradation of Phenol over a Hybrid Organo-Inorganic Material: Iron(II) Hydroxyphosphonoacetate

Water treatment is a hot topic, and it will become much more important in the decades ahead. Advanced oxidation processes are being increasingly used for organic contaminant removal, for example using photo-Fenton reactions. Here we report the use of an organo-inorganic hybrid, Fe[HO3PCH(OH)COO]·2H2O, as Fenton photocatalyst for phenol oxidation with H2O2 under UVA radiation. Preactivation, catalyst content, and particle size parameters have been studied/optimized for increasing phenol mineralization. Upon reaction, iron species are leached from the catalyst making a homogeneous catalysis contribution to the overall phenol photo-oxidation. Under optimized conditions, the mineralization degree was slightly larger than 90% after 80 min of irradiation. Analysis by X-ray photoelectron spectroscopy revealed important chemical modifications occurring on the surface of the catalyst after activation and phenol photodegradation. The sustained slow delivery of iron species upon phenol photoreaction is advantageous as the mixed heterogeneous−homogeneous catalytic processes result in very high phenol mineralization.Proyecto nacional MAT2010-1517

Al,Fe,Ni-pillared bentonite in the catalytic wet peroxide oxidation of the textile dye Acid Yellow 99

The main goal of this work was to prove that nickel containing Al,Fe pillared bentonites have enhanced catalytic properties. The chosen test system was the catalytic wet peroxide oxidation (CWPO) the Acid Yellow 99 dye (AY99) with the initial concentration of 50 mg dm(-3), the amount of H2O2 that exceeded the stoichiometric one, 60 A degrees C, magnetic stirrer, atmospheric pressure. Bentonite was successfully pillared with AlFe and AlFeNi polyoxo cations. The chemical composition of the synthesized samples was: SiO2 56.5, Al2O3 31.3, Fe2O3 9.2; SiO2 56.4, Al2O3 31.9, Fe2O3 8.9 and NiO 0.1; SiO2 61.1, Al2O3 31.3, Fe2O3 4.8 and NiO LT 0.01 for AlFe10-PILC, AlFe10Ni5-PILC and AlFe5Ni5-PILC, respectively. The values of textural property parameters decreased in the following order AlFe10-PILC > AlFe10Ni5-PILC > AlFe5Ni5-PILC. Almost complete decolorization was achieved using all synthesized catalysts and followed first order kinetics. AlFe10Ni5-PILC induced the highest decolorization rate. Somewhat higher decolorization rate in the presence of AlFe10Ni5-PILC in comparison with AlFe5Ni5-PILC can probably be ascribed to one of the following properties or their combined effect: higher Fe content and more developed porous structure. Adsorption of AY99 on AlFe5Ni5-PILC and its degradation by H2O2 (without catalyst) were investigated in order for their influence on the decolorization of AY99, in comparison with that of CWPO using AlFe10Ni5-PILC, to be estimated. The adsorption was the least efficient, followed by degradation using H2O2 (without catalyst). CWPO was more efficient when compared to adsorption and degradation by H2O2 together. CWPO using Al,Fe,Ni-PILC can be regarded as promising method for degradation of azo dyes

Influence of Hydrogen Annealing on the photocatalytic activity of diamond supported gold catalysts

Fenton-treated diamond nanoparticles have been submitted to hydrogen reduction at 500 °C with the purpose of modifying the nature of the functional groups present on the diamond surface. The nature of the functional groups on the diamond samples was characterized by a combination of spectroscopic and analytical techniques. In particular, Fouriertransformed infrared spectroscopy, temperature-programmed desorption, and X-ray photoelectron spectroscopy (XPS) show the decrease in the population of carboxylic acids, esters, and anhydrides after hydrogen treatment. XPS also shows a decrease on the oxygen content after the hydrogen treatment of the diamond nanoparticles and lower electronegativity of the carbons as assessed by the lower binding energy values. Although Fentontreated diamond colloids in water changes the zeta potential from positive to negative values as a function of the pH, hydrogen annealing and the disappearance of the carboxyl groups determines that the zeta potential of the resulting sample remains positive in the complete pH range. Deposition of gold nanoparticles was carried out by the polyol method consisting on the reduction of HAuCl4 by hot ethylene glycol in the presence of the support. TEM analysis shows a variation of the average gold nanoparticle size that decreases after hydrogen reduction of carboxylic groups and becomes smaller for low gold loadings. The catalytic activity of the diamond supported gold nanoparticles as a function of the surface annealing treatment and gold loading was evaluated for the natural sunlight-assisted peroxidation of phenol by H2O2. It was observed that the most efficient sample was the one having lower gold nanoparticle size that was obtained for diamond samples reduced by hydrogen at 500 °C after the Fenton treatment and having low gold loading (0.05 wt %). Turnover frequencies above 2400 and 940 h−1 were obtained for phenol degradation and H2O2 decomposition, respectively.Financial support by the Spanish Ministry of Economy and Competitiveness (MINECO, Severo Ochoa program and CTQ 2012-32315), Universidad Politecnica de Valencia (PAID-06-11, no 2095) and Generalitat Valenciana (Prometeo 2013/014 and GV/2013/040).Navalón Oltra, S.; Sempere Aracil, D.; Alvaro Rodríguez, MM.; García Gómez, H. (2013). Influence of Hydrogen Annealing on the photocatalytic activity of diamond supported gold catalysts. ACS Applied Materials and Interfaces. 5(15):7160-7169. https://doi.org/10.1021/am401489nS7160716951