RESUMEN
The present study aimed to prepare catalysts of Fe- and Cu-loaded zeolite via ion-exchange technique using dilute solutions of metal nitrate precursors followed by calcination at 600°C in the air for 4â h. Commercial zeolite ZSM-5 with specific surface area of 400â m2/g and diameter particle of 1.2-2â mm was used as a parent support. The prepared catalysts were characterized by Fourier transform infrared spectroscopy analysis. The IR absorbed bands of Cu-ZSM-5 and Fe-ZSM-5 revealed a shift in the frequency and a reduction in the intensity framework. This indicates that both catalysts have a significant change in the number of the zeolite structure bonds. The catalytic activity of the prepared materials compared to the parent zeolite was evaluated for the catalytic ozone decomposition. The ozone stream of the initial concentration (13â g/m3) with air flow rate (Q) of 0.18â m3/h was passed through a glass jacket column reactor filled with a fixed bed of 40â g zeolites. It was showed that the ozone removal efficiency by Cu-ZSM-5 and Fe-ZSM-5 was obviously higher than that found with the parent ZSM-5. In terms of O3 removal efficiency, zeolite samples could be ranked as follows: Fe-ZSM-5 > Cu-ZSM-5> parent ZSM-5. The results revealed about 90% O3 removal efficiency for Fe-ZSM-5 and 70% for Cu-ZSM-5 as compared to nearly 40% for the parent zeolite. Consequently, the incorporation of Fe and Cu metals onto the zeolite surface plays a key role for enhancing the gaseous ozone elimination.
Asunto(s)
Contaminación del Aire Interior , Ozono/química , Catálisis , Metales , ZeolitasRESUMEN
A sequential adsorption/photocatalytic regeneration process to remove tartrazine, an azo-dye in aqueous solution, has been investigated. The aim ofthis work was to compare the effectiveness of an adsorbent/photocatalyst composite-TiO2 deposited onto activated carbon (AC) - and a simple mixture of powders of TiO2 and AC in same proportion. The composite was an innovative material as the photocatalyst, TiO2, was deposited on the porous surface ofa microporous-AC using metal-organic chemical vapour deposition in fluidized bed. The sequential process was composed of two-batch step cycles: every cycle alternated a step of adsorption and a step of photocatalytic oxidation under ultra-violet (365 nm), at 25 degreeC and atmospheric pressure. Both steps, adsorption and photocatalytic oxidation, have been investigated during four cycles. For both materials, the cumulated amounts adsorbed during four cycles corresponded to nearly twice the maximum adsorption capacities qmax proving the photocatalytic oxidation to regenerate the adsorbent. Concerning photocatalytic oxidation, the degree of mineralization was higher with the TiO2/AC composite: for each cycle, the value of the total organic carbon removal was 25% higher than that obtained with the mixture powder. These better photocatalytic performances involved better regeneration than higher adsorbed amounts for cycles 2, 3 and 4. Better performances with this promising material - TiO2 deposited onto AC - compared with TiO2 powder could be explained by the vicinity of photocatalytic and AC adsorption sites.
Asunto(s)
Carbón Orgánico/química , Colorantes/química , Fotoquímica/métodos , Tartrazina/química , Titanio/química , Contaminantes Químicos del Agua/química , Purificación del Agua/métodos , Catálisis , Carbón Orgánico/efectos de la radiación , Colorantes/efectos de la radiación , Luz , Materiales Manufacturados , Tartrazina/efectos de la radiación , Titanio/efectos de la radiación , Agua/química , Contaminantes Químicos del Agua/efectos de la radiaciónRESUMEN
Preparation of activated carbon from sewage sludge is a promising approach to produce cheap and efficient adsorbent for pollutants removal as well as to dispose of sewage sludge. The first objective of this study was to investigate the physical and chemical properties (BET surface area, ash and elemental content, surface functional groups by Boehm titration and weight loss by thermogravimetric analysis) of the sludge-based activated carbon (SBAC) so as to give a basic understanding of its structure and to compare to those of two commercial activated carbons, PICA S23 and F22. The second and main objective was to evaluate the performance of SBAC for single and competitive adsorption of four substituted phenols (p-nitrophenol, p-chlorophenol, p-hydroxy benzoic acid and phenol) from their aqueous solutions. The results indicated that, despite moderate micropore and mesopore surface areas, SBAC had remarkable adsorption capacity for phenols, though less than PICA carbons. Uptake of the phenolic compound was found to be dependent on both the porosity and surface chemistry of the carbons. Furthermore, the electronegativity and the hydrophobicity of the adsorbate have significant influence on the adsorption capacity. The Langmuir and Freundlich models were used for the mathematical description of the adsorption equilibrium for single-solute isotherms. Moreover, the Langmuir-Freundlich model gave satisfactory results for describing multicomponent system isotherms. The capacity of the studied activated carbons to adsorb phenols from a multi-solute system was in the following order: p-nitrophenol > p-chlorophenol > PHBA > phenol.
Asunto(s)
Carbono/química , Fenoles/química , Eliminación de Residuos/métodos , Aguas del Alcantarillado/química , Contaminantes Químicos del Agua/química , Adsorción , Metales Pesados/química , Modelos Químicos , Fenoles/aislamiento & purificación , Termogravimetría , Contaminantes Químicos del Agua/aislamiento & purificación , Purificación del Agua/métodosRESUMEN
The effect of ultrasound on the pseudo-solubility of nitrogen in water and on gas-liquid mass transfer kinetics has been investigated in an autoclave reactor equipped with a gas induced impeller. In order to use organic liquids and to investigate the effect of pressure, gas-liquid mass transfer coefficient was calculated from the evolution of autoclave pressure during gas absorption to avoid any side-effects of ultrasound on the concentrations measurements. Ultrasound effect on the apparent solubility is very low (below 12%). Conversely ultrasound greatly improves gas-liquid mass transfer, especially below gas induction speed, this improvement being boosted by pressure. In typical conditions of organic synthesis: 323 K, 1100 rpm, 10 bar, k(L).a is multiplied by 11 with ultrasound (20 kHz/62.6 W). The impact of sonication is much higher on gassing out than on gassing in. In the same conditions, this enhancement is at least five times higher for degassing.