RESUMEN
In this study, a single factor exploration method was adopted to optimize the cotton shell-based activated carbon adsorption reaction time, temperature, pH value, initial concentration of cadmium ion, and other conditions. The experimental results showed that under the conditions of Cd2+ solution pH = 8, initial concentration of 100 mg/L, adsorption reaction time of 180 min, adsorption temperature of 45 °C, cotton shell-based activated carbon dosage of about 0.1 g, the removal rate of Cd2+ was 94.03%, the adsorption capacity was 51.95 mg/g, and the error was only 0.05%. The adsorption kinetic analysis of this study conforms to the quasi-second-order kinetic model, the adsorption isotherm analysis conforms to the Langmuir adsorption isothermal model, and the Gibbs free energy of the adsorption process is negative; the above simulation analysis also proves the spontaneity and feasibility of the adsorption process.
RESUMEN
A facile, one-step synthesis of carbon nanotube (CNT)-loaded Ag/AgBr is reported. The as-prepared samples were characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), UV/Vis absorption spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, photoluminescence (PL) spectroscopy and electrochemical impedance spectroscopy (EIS). The CNT/Ag/AgBr composite exhibited much higher photocatalytic activity than pure Ag/AgBr in degrading methyl orange (MO) dye solution. The loading amount of CNT had a significant influence on the photoactivity of the CNT/Ag/AgBr composite. When the CNT loading amount was 1.4 at%, the hybrid material showed the highest photocatalytic ability. The result showed that a small amount of CNT was beneficial for photo-generated electron transfer, which could enhance the photoactivity of CNT/Ag/AgBr. The degradation dye solution was tested by liquid chromatography/mass spectrometry (LC/MS) and total organic carbon (TOC) analysis. Based on the results, the structure of the synthesized CNT/Ag/AgBr hybrid material was verified and the possible degradation path of the MO dye was proposed. A possible visible-light photocatalytic degradation mechanism was also discussed.
RESUMEN
The effects of calcination temperature and feedstock pretreatment on the catalytic performance of Co/γ-Al(2)O(3) catalysts were studied for partial oxidation of methane (POM) to synthesis gas, with emphasis on the role of feedstock pretreatment. The physicochemical properties of the catalysts were characterized by N(2) adsorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), H(2) temperature-programmed reduction (H(2) -TPR), and Raman spectroscopy. The results showed that the pretreatment of the catalyst by reaction gas significantly improved the catalytic activity and stability for the POM reaction. On the other hand, the effect of calcination temperature was less significant. Although the initial activity was increased by an increased calcination temperature, the catalyst without the feedstock pretreatment suffered a rapid deactivation. The reaction-atmosphere pretreatment was revealed as a process that mainly modified the surface structure of the catalyst. In that process, the formation of a CoAl(2)O(4) -like compound led to high Co metal dispersion after reduction, and the transformation of the carrier into α-Al(2)O(3) occurred over the catalyst surface. Both the high dispersion of cobalt and the presence of α-Al(2)O(3) surface phase were assumed as the important factors resulting in an excellent catalytic performance in terms of high activity and high stability.
RESUMEN
A novel heterojunction AgBr/BiPO(4) photocatalyst was synthesized with the hydrothermal method. The photocatalyst was characterized by X-Ray powder Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectrometry (EDS), Transmission Electron Microscopy (TEM), X-ray Photoelectron Spectrscopy (XPS) and Diffuse Reflectance Spectroscopy (DRS). The XRD, SEM-EDS, TEM and XPS analyses indicated that the heterojunction structure formed during the process of hydrothermal treatment. The photocatalytic activity of the photocatalysts was evaluated by degradation of methylene blue dye (MB). The results indicated that the AgBr/BiPO(4) heterojunction exhibited a much higher photocatalytic activity than the pure BiPO(4). The mechanism of the enhancing AgBr/BiPO(4) heterojunction's photocatalytic activity was discussed. It was also found that the photocatalytic degradation of MB over AgBr/BiPO(4) heterojunction photocatalysts followed the pseudo-first-order reaction model.
RESUMEN
Catalytic partial oxidation of methane (POM) to synthesis gas (syngas) over Pt/Al(2)O(3) was investigated by in situ microprobe Raman and pulse reaction methods with attention focused on the mechanism of syngas formation in the oxidation zone (i.e., the catalyst zone in which O(2) was still available in the reaction feed). It was found that the amount of platinum oxide in the catalyst under POM conditions was below the detection level of Raman spectroscopy. Raman bands of carbon species that originated from methane dissociation were detected at the entrance of the catalyst bed under working conditions. The results of the pulse reaction study on POM as well as steam and CO(2) reforming of methane at 700 °C with a contact time of less than 1 ms over the catalyst suggest that pyrolysis of methane on reduced platinum sites followed by coupling of two surface hydrogen atoms to H(2) and partial oxidation of surface carbon species to CO are the major reactions responsible for syngas formation in the oxidation zone. Under the experimental conditions, steam and CO(2) reforming of methane play only a minor role in syngas formation in the same reaction zone. The contribution of the last two reactions increases with increasing contact time.