ABSTRACT
In this study, 8, 25 and 50 wt% Fe3O4@activated carbon (AC) catalysts were prepared by simple coprecipitation method. The efficiency of the catalysts for the advanced Fenton's oxidation process using methylene blue (MB) as a model substrate was tested. Both modified and unmodified activated carbon catalysts exhibited similar activity towards the Fenton's oxidation process. Therefore, it is difficult to identify the role of the catalyst in this dye removal process. Hence, we proposed a new methodology to remove the MB by adopting the adsorption process initially, followed by the Fenton's oxidation process. The proposed process significantly improved the methylene blue decomposition reaction over the 25 wt% Fe3O4@AC catalyst. However, this trend was not seen in pure activated carbon and Fe3O4@AC (8 and 50 wt%) catalysts due to the instability of the material in the oxidizing medium. The possible reason for the deactivation of the catalysts was evaluated from lattice strain calculations, as derived from the modified W-H models (Uniform Deformational Model (UDM), Uniform Stress Deformation Model (USDM) and Uniform Deformation Energy Density Model (UDEDM)). These results provided a quantitative relationship between the experimentally calculated lattice strain values and Fenton's catalytic activity. Furthermore, the optimized strain value and crystalite size of Fe3O4 on the activated carbon matrix are responsible for the high catalytic activity.
ABSTRACT
The Ce1-xMnxO2 nanocatalysts (x = 0.25, 0.50 and 0.75 wt.%) were synthesized by sol-gel method. The catalysts were characterized using various techniques such as XRD, N2 sorption study, DRSUV-Vis, TPR, SEM and TEM. The incorporation of Mn ions into the ceria lattice was confirmed by XRD analysis. DRUV-Vis spectra confirm the presence of Ce3+ ions in the lattice of Ce1-xMnxO2. H2-TPR study revealed the oxygen storage capacity of the catalyst. The 3D flowerlike morphology of the nanocatalysts was confirmed from FESEM and HRTEM images. The catalytic activity was tested for the vapor phase oxidation of cyclohexane using air as an oxidant. The key reaction parameters were varied to study the stability, activity and selectivity of the catalysts. The study concluded that suitable amount of manganese content is essential for the selective oxidation of cyclohexane at low temperature and Ce0.25Mn0.75O2 is the most suitable catalyst for high conversion and selectivity under the given reaction conditions. The activity of the catalyst is correlated with the characterization results.
ABSTRACT
Both serotonin (5-HT) and gamma-aminobutyric acid (GABA) modulate female rat lordosis behavior and appear to interact in their control of the behavior. The current experiments were designed to investigate the interaction between these two neurotransmitters in sexually receptive female rats. Ovariectomized female rats, with bilateral cannulae directed toward the ventromedial nucleus of the hypothalamus (VMN), were hormonally primed with 10 microg estradiol benzoate and 500 microg progesterone. Sexual behavior was examined after intracranial infusion with 200 ng (+/-)-8-hydroxy 2-(di-n-propylamino)tetralin (8-OH-DPAT), 25 ng (5-aminomethyl-3-hydroxyisoxazole)hydrobromide (muscimol), 10 ng bicuculline or a combination of the drugs. As expected, 8-OH-DPAT reduced lordosis behavior and muscimol attenuated this inhibition in a bicuculline-sensitive manner. Muscimol alone also reduced lordosis behavior. These findings contrast with several reports that muscimol facilitates lordosis behavior of suboptimally hormonally primed female rats. The current outcome is discussed in terms of procedural differences between the present experiment and earlier studies. It is suggested that muscimol may enhance lordosis responding in suboptimally hormonally primed rats by activation of GABAA receptors located dorsal to the VMN. In contrast, activation of receptors located more ventrally within the mediobasal hypothalamus (MBH) may inhibit the behavior of rats that are already sexually receptive.