Jorge Villaseñor

Acid-catalysed hydrolysis of rice hull : Evaluation of furfural production

Abstract One- and two-stage processes to obtain furfural from rice hull were examined. When the reaction was carried out in an autoclave at different liquid/solid ratios and sulphuric acid concentrations, a low production of furfural was observed. Metallic oxides catalysed the conversion and enhanced furfural production. In a two-stage process (pre-hydrolysis and dehydration) the yield was the highest and critical variables were solid/liquid ratio and acid concentration in the dehydration. Metallic oxides and chlorides increased the furfural production.

Photocatalytic degradation of pentachlorophenol on TiO2 sol-gel catalysts.

The photocatalytic degradation of pentachlorophenol (PCP) in aqueous solution was investigated using TiO2 catalysts. The samples were prepared by the sol-gel method using different gelation pH and different calcination temperatures. The solids were characterized by specific surface area, X-ray diffraction, UV-Vis absorbance, FTIR and pentachlorophenol adsorption. The catalytic activity of the solids was evaluated in a conventional photoreactor at 298 K using 30 ppm of pentachlorophenol. It was found that the reaction follows a first-order reaction and the kinetic constant values change slightly with the pH of gelation and more significantly with the calcination temperature.

Photodegradation of pentachlorophenol on ZnO

The photocatalytic degradation of pentachlorophenol on ZnO catalysts is reported. The studies were carried out in a conventional photoreactor at 298 K using 30 ppm of pentachlorophenol. Appropriate catalytic activity and high selectivity to mineralization products were found. A significant increase in the conversion was achieved at higher temperatures. No direct relationship between catalytic activity and specific area or bandgap was found.

ZnO-catalysed photodegradation of kraft black liquor

Abstract Kraft black liquor was used as a model for effluent from the pulp and paper industry. Photochemical bleaching was attained when dilute samples were photolyzed with UV radiation using ZnO as catalyst. The photochemical mineralization of organic matter was first order and dependent on the oxygen pressure. A catalyst doped with Ag showed little effect on the discoloration or decrease in the chemical oxygen demand (COD) of black liquor. Platinum-impregnated ZnO yielded 100% discoloration after 60 min (190 kJ m−2) of UV radiation. Gel chromatography profiles and CO2 evolution measurements confirm the photomineralization of organic matter.

Effect of temperature on kraft black liquor degradation by ZnO-photoassisted catalysis

The ZnO-photocatalysed reaction of kraft black liquor, obtained from P. radiata pulping, was studied to determine the kinetic parameters that govern CO2 evolution. The mineralization reaction exhibits a first-order dependence on the dissolved oxygen concentration and a half-order dependence on the concentration of the substrate at 25°C. The catalysed reaction accounts for more than 95% of the CO2 production, at all temperatures studied, and the uncatalysed reaction accounts for 5%. The apparent activation energy of the catalysed process was estimated to be 43.1 kJ mol−1.

Fe Supported Catalysts Prepared by The Sol-Gel Method. Characterization and Evaluation in Phenol Abatement

Iron supported catalysts containing 10 wt% of iron, as oxide, on TiO2 and Al2O3 have been prepared by the sol gel method and the traditional method based of the impregnation of the support with the metal precursor on commercial and sol-gel supports. The samples were characterised by measuring the specific area (SBET), temperature programmed reduction (TPR), infrared spectroscopy (FTIR), electrophoretic migration (IP), chemical oxygen demand (COD) and X-ray diffraction (XRD). The catalytic activity was measured in a batch reactor using ozone as oxidizing agent. It was found presence of highly dispersed iron oxide in the samples prepared by cogelation, whereas in those prepared by impregnation of the iron precursor, the dispersion was very poor. Catalytic activity indicates that phenol is degraded with a low mineralization to CO2.

High-Intensity Exercise Reduces Cardiac Fibrosis and Hypertrophy but Does Not Restore the Nitroso-Redox Imbalance in Diabetic Cardiomyopathy

Diabetic cardiomyopathy refers to the manifestations in the heart as a result of altered glucose homeostasis, reflected as fibrosis, cellular hypertrophy, increased oxidative stress, and apoptosis, leading to ventricular dysfunction. Since physical exercise has been indicated as cardioprotective, we tested the hypothesis that high-intensity exercise training could reverse the cardiac maladaptations produced by diabetes. For this, diabetes was induced in rats by a single dose of alloxan. Diabetic rats were randomly assigned to a sedentary group or submitted to a program of exercise on a treadmill for 4 weeks at 80% of maximal performance. Another group of normoglycemic rats was used as control. Diabetic rat hearts presented cardiomyocyte hypertrophy and interstitial fibrosis. Chronic exercise reduced both parameters but increased apoptosis. Diabetes increased the myocardial levels of the mRNA and proteins of NADPH oxidases NOX2 and NOX4. These altered levels were not reduced by exercise. Diabetes also increased the level of uncoupled endothelial nitric oxide synthase (eNOS) that was not reversed by exercise. Finally, diabetic rats showed a lower degree of phosphorylated phospholamban and reduced levels of SERCA2 that were not restored by high-intensity exercise. These results suggest that high-intensity chronic exercise was able to reverse remodeling in the diabetic heart but was unable to restore the nitroso-redox imbalance imposed by diabetes.

CATALYTIC OZONATION OF OXALIC ACID WITH MnO2/TiO2 AND Rh/TiO2

The catalytic ozonation of oxalic acid in a batch reactor using TiO2, MnO2/TiO2 and Rh/TiO2 as catalysts was studied. The presence of the catalyst significantly improves the ozonation rate in comparison with the non-catalytic reaction. The adsorption and the extent of degradation of oxalic acid were found to be dependent on the solutions pH. Higher degradation rates were found for catalytic systems at pH 2.5, where the oxalic acid concentration in the water phase was almost completely removed. The contribution of the MnO2/TiO2 and Rh/TiO2 catalysts as well the TiO2 support is discussed. The highest mineralization, expressed as CO2 evolution, was reached with the MnO2/TiO2 catalyst at pH 2.5

ESTUDIO DE REDUCCIÓN FOTOCATALIZADA DE CROMO HEXAVALENTE

Se propone una metodologia para disminuir la concentracion de Cr(VI) presente en efluentes de curtiembre sin tratamiento previo. La propuesta se basa en un proceso fotocatalitico donde se irradia el efluente por un determinado tiempo con luz ultravioleta en presencia de oxido de titanio como catalizador, empleando como agente reductor formaldehido. Se utilizo sistemas modelo de soluciones de Cr(VI) de 100 mg/L a distintos pH con diferentes cantidades de catalizador y tiempos de irradiacion. La optimizacion de las variables se realizo a traves de analisis multi-variado Las condiciones optimas para reducir 50 ml de Cr(VI) de 100 mg/L, se obtuvo a pH 2, con un tiempo de irradiacion de 20 minutos y 40,0 mg de TiO2, logrando para el sistema modelo un 97,8 % de reduccion de Cr(VI) y para el efluente de curtiembre un 81,3 %.

Monitoring of β-blockers ozone degradation via electrospray ionization mass spectrometry

The structures of intermediate products of ozone degradation of different pharmaceutical compounds have been studied. Under the conditions employed, complete ozone degradation of nadolol was achieved after 100 min. The degradation products obtained in aqueous solution were characterized by electrospray ionization mass (and tandem mass) spectrometry (ESI-MS and ESI-MS/MS). The proposed mechanism for degradation, ozone attacks at the aniline amino group giving rise to nitro compounds and further degradation occurs via a series of oxidative processes. Continuous online monitoring by ESI-MS(/MS) with high accuracy mass measurements showed that ozone degradation of atenolol (ATE) and acebutolol (ACE) occurs via mechanisms similar to that of nadolol