The adsorption kinetics of pure CO2, N2 and CH4 on a natural clinoptilolite (ZSL) sample from Villa de Reyes (San Luis Potosí, México) were measured at different temperatures using a glass, high-vacuum volumetric system. The ability of the natural zeolite to adsorb these gases depended on the gas–adsorbent contact time, t. For short values of t, the gas adsorption uptakes decreased in the order CO2 >> N2 > CH4. However, for long t values, the adsorption uptakes decreased in the sequence CO2 > CH4 > N2. It was established that the activation energies (kJ/mol) for the adsorption process increased in the following order CO2 (15) < N2 (18) < CH4 (40), correlating fairly well with the increasing order of kinetic diameter (Å) of the molecules: CO2 (3.3) < N2 (3.64) < CH4 (3.8). In comparison to the ZSL sample, the rate of adsorption of N2 and CH4 on H-ZSL increased and the total adsorption capacity decreased. The ZSL sample may be recommended as an effective adsorbent for the separation of CO2/CH4 and N2/CH4 mixtures.

Samples of mesoporous silica, SBA-15, were prepared under hydrothermal conditions and Cu cations were incorporated into the framework by two different impregnation techniques. The corresponding adsorption/desorption isotherms of propylene, propane, and N 2 were measured to evaluate the material's effectiveness in the separation of propane/propylene mixtures.Adsorption uptake of propylene increased and that of propane decreased in Cu containing samples as compared to the uptakes observed in undoped SBA-15 samples. It was demonstrated that the presence of Cu atoms in the adsorbent lattice led to a greater selectivity towards propylene. Furthermore, the highest level of Cu(I) were obtained in samples prepared by equilibrium impregnation, which in turn improved the olefin/paraffin uptake ratio. Under some working conditions, the amount of propylene adsorbed in selected samples is totally reversible while propane uptake was negligible. E. I. Basaldella ( ) •

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In this study, the adsorption equilibria and kinetics of pure propane (C3H8) and propylene (C3H6) on natural erionite (ERI), from Agua Prieta (Sonora, Mexico), and on cation-exchanged erionite samples (K-ERI and Ag-ERI) have been measured at different temperatures using a glass high-vacuum volumetric device. All of the samples showed selectivity toward propylene. The ion-exchange treatment influenced, remarkably, the C 3H8 and C3H6 adsorption behaviors. The adsorbed amounts of both hydrocarbons on K-ERI and Ag-ERI samples were lower than those on ERI, a result that can be ascribed to a decrease in micropore volume. It was established that the adsorptive separation of these gases on K-ERI could be effected most efficiently at 111 °C for gas-adsorbent contact times in the range 20-100 s, whereas the Ag-ERI sample could be recommended for this separation for the temperature range 50-80 °C and for short gas-adsorbent contact times in the interval 10-30 s.

Palabras clave: digestión anaerobia, biogás, inóculo, sustrato RESUMENEn este trabajo se estudia mediante el proceso de digestión anaerobia (DA), la descomposición de materia orgánica de residuos alimenticios de cocina (sustrato) con lodo (inóculo) de una planta de tratamiento de aguas residuales con la finalidad de obtener biogás y determinar el potencial bioquímico de metano (PBM) al final del proceso. Los ensayos que se llevaron a cabo fueron con relaciones sustrato:inóculo (S:I) 1:2 y 1:3, en términos de sólidos volátiles (SV). En el transcurso de la DA en condiciones mesofílicas (35 ºC) y tiempos de residencia (TR) de 15 días, se midieron los parámetros más importantes que influyen en esta digestión: SV, sólidos totales (ST), demanda química de oxígeno (DQO) y pH. El biogás obtenido se purificó por medio de la eliminación de H 2 S y NH 3 con trampas de NaOH y H 2 SO 4 1M. En el caso de los experimentos con inóculo y sustrato se recuperaron en promedio 1.235 L de biogás con un 80.15 % de CH 4 y en los ensayos con inóculo sin sustrato 0.720 L de biogás con 90.47 % de CH 4 . La cuantificación de este gas se llevó a cabo por cromatografía de gases. Los resultados que se obtuvieron concuerdan favorablemente con la producción de biogás y la disminución de la materia o carga orgánica expresada como DQO. En la determinación de PBM se obtuvieron 124.82 y 127.89 mL CH 4 /g SV para experimentos S:I-1:3 y para la relación 1:2, 103.39 y 116.27 mL CH 4 /g SV.Key words: anaerobic digestion, biogas, inoculum, substrate ABSTRACTIn this work we studied the decomposition of organic matter of food kitchen wastes (substrate) by sewage sludge (inoculum) from a wastewater treatment plant, through the process of anaerobic digestion (AD) in order to obtain biogas and to determine the biochemical methane potential (BMP) at the end of this process. The tests were performed with substrate:inoculum ratios 1:2 and 1:3, in terms of volatile solids (VS).