The adsorption capacities of two synthesized zeolites (crystalline ZSM-5 and semi-crystalline faujasite Y) for a mixture of indole, quinoline and carbazole were studied. The different samples obtained show different crystalline degree, mesoporosity and Si/Al ratios. The synthesis procedure is based on the simultaneous depolymerization of a mixture of high surface area silica, such as rice hull ashes (RHA), and a crystalline zeolite, such as clinoptilolite or faujasite. The depolymerization step is followed by a partial reorganization induced by a structure-directing agent. A model mixture of nitrogenous compounds was prepared, then it was mixed with the zeolite samples and the amount adsorbed of nitrogenous compounds was determined by gas chromatography. Analysis of the adsorbed molecules reveals selectivity in favor of quinoline, followed by indole and then carbazole. The best adsorbent properties correspond to the solid with highest porous volume. The samples obtained were characterized by X-ray diffraction, 29Si and 27Al magic-angle spinning nuclear magnetic resonance, X-ray fluorescence and Fourier transform infrared spectroscopy. The Barrett-Joyner-Halenda (BJH) pore size distribution and the Brunauer-Emmet-Teller (BET) surface area values were obtained from N2 adsorption/desorption isotherms.

4A Zeolite was synthesized using rice husk ash (RHA) as a raw material in a microwave-assisted hydrothermal synthesis. Two new procedures were proposed: procedure A, using RHA as the raw material, and procedure B, using the depolymerized RHA. Both procedures were performed using microwave-assisted hydrothermal synthesis, and neither synthesis required an aging time. Crystallinities of over 90 and 80% were reached at 100 ºC after 30 min of microwave heating for procedures A and B, respectively. The obtained zeolites were used as warm mix asphalt additives, and the performance of the zeolite obtained from procedure A was better. Additionally, the zeolite obtained from procedure A and commercial silane were used separately as asphalt-aggregate adhesion promoter. An increase in the adhesion percentage from 30% of a blank sample to 94% was observed.

Rice hull ash was prepared via a fast chemical combustion method with ammonium nitrate, urea and milled rice hull. Urea was used as the chemical fuel. The mixture was heated to various temperatures (100 to 1000 °C), and the resulting products were compared with products obtained via calcination, in which samples were heated to the same temperatures for 2 hours. Changes in the structure, morphology, texture and surface fractal dimensions with respect to temperature were examined and found to be highly relevant for adsorption applications. The prepared powders were characterized physicochemically by X-ray diffraction and N2-physisorption measurements. The surface fractal dimensions of the prepared materials were calculated from N2-adsorption-desorption isotherms. The results indicate that the fast combustion samples have larger surface fractal dimensions than calcined samples. A correlation between fractal dimensions and Co2+ ion adsorption was found. The present study demonstrates the importance of textural properties and surface fractal dimensions in the adsorption performance of adsorbents.

A method is presented in which gas chromatography coupled with mass spectrometry (GC-MS) allows quantitative simultaneous detection of mixtures of phenol (Ph), 2-chlorophenol (2-CPh), 3-cholorphenol (3-CPh), and 4-cholorophenol (4-CPh) in aqueous mixtures after being adsorbed on silicalita-1, utilizing selected-ion monitoring (SIM) and full-scan modes mass selective detection. GC-MS with SIM at m/z = 64 and m/z = 128 showed good detection selectivity for mixtures of Ph, 2-CPh and 3-CPh (M1), and 2-CPh and 4-CPh (M2). Silicalita-1 was obtained from an amorphous organo-alumino-silicic gel from rice husk, an abundant and low cost agricultural waste residue that is readily available in large quantities. This product was used as a sorbent for solid phase extraction of organic analytes from aqueous solutions. The adsorption of the three chlorophenol isomers, ortho-, meta-, and para-, by silicalite-1 has been studied independently, showing that meta- and para-chlorophenol isomers are adsorbed more than ortho-chlorophenol. However the adsorption behavior of mixtures of these isomers was not reported. In this work, it was found that when the ortho-isomer is mixed either with meta-or para-chlorophenol, considerable differences were observed in the adsorption process; in the studied mixture, the ortho-isomer was adsorbed more than the meta-and para-chlorophenol.

En este trabajo se presenta un método cromatográfico acoplado a la espectrometría de masas (GC-MS) que permite la detección simultánea de fenol(Ph), 2-clorofenol (2-CPh), 3-clorofenol (3-CPh), y 4-clorofenol (4-CPh) en mezclas acuosas después de ser adsorbidas sobre silicalita-1, utilizando iones previamente seleccionados y el espectro completo de iones. Los iones en SIM de m/z = 64 y 128 mostraron una buena detección y selectividad para mezclas de Ph, 2-CPh, y 3CPh (M1) y 2-CPh y 4-Cph (M2). La silicalita-1 se obtuvo a partir de un gel órgano-alumino-silícico amorfo proveniente de cáscara de arroz, material abundante y de bajo costo, dado que proviene de residuos agrícolas disponibles fácilmente en grandes cantidades. Este producto se utilizó como un sorbente en la extracción en fase sólida de analitos orgánicos a partir de soluciones acuosas. La adsorción de los tres isómeros de clorofenol, orto, meta, y para, por la silicalita-1 ha sido estudiada de forma independiente, mostrando que los isómeros meta y para clorofenol se adsorben más que el orto-clorofenol. Sin embargo, el comportamiento de adsorción de mezclas de estos isómeros no se ha reportado. En este trabajo, se ha encontrado que cuando el isómero orto se encuentra en mezcla con el meta o para-clorofenol presentan diferencias considerables, como se observó en el proceso de adsorción; en la mezcla estudiada el isómero orto se adsorbe más que el meta y para-clorofenol.