سال:1392 | دوره: | شماره: |تعداد مقالات:4

Sulfonic acid functionalized ordered nanoporous sodium montmorillonite was easily prepared by the reaction of sodium montmorillonite with chlorosulfonic acid. The new catalyst demonstrated efficient and chemoselective methoxymethylation reaction of alcohols with formaldehyde dimethyl acetal in chloroform under reflux conditions. This reaction affords corresponding ethers in good to excellent yields. The present method offers several advantages such as short reaction times, high yields, simple procedure, mild conditions, heterogeneous nature, and reusability of the catalyst.

This work presents a study of the adsorption properties of nanostructures. The moving gas technique was employed to determine the transient and steady-state response behavior of nanocrystalline gas sensors. SnO2 sensors have shown high sensitivity to low concentrations of ethanol at moderate temperature. Tin dioxide is the most used material for gas sensing because its three-dimensional nanofilms and properties are related to the large surface exposed to gas adsorption. This study proposes the use of SnO2 nanofilms in interaction with ethanol; we used different percentages of SnO2 and WO3 in the adsorption of ethanol by nanofilms. The total energy, potential energy, and kinetic energy were calculated for the interaction between nanofilms and ethanol at different concentrations and at 300 K. The calculations were achieved by Langevin dynamics and Monte Carlo simulation methods. The total energy decreased with additional tungsten percentage in the nanofilms and increased with additional number of ethanol molecules and interactions between them are endothermic.

Acid green 25 (AG) dye was adsorbed from water by using polyaniline nanotubes (PANI NT) salt/silica composite as adsorbent. Comparison between the removal of the dye by using PANI NT salt/silica composite and the conventional PANI salt/silica composite was investigated. This result was evidenced from the measurements of the UV-visible absorbance of AG dye solutions after different times. Experiments were conducted by varying parameters, namely initial concentration of the dye and contact time. The percentage of color removal decreased with increase in initial dye concentration. Adsorption equilibrium of color removal was reached after 60 min of contact time. Equilibrium data were fitted to Langmuir, Freundlich, and Tempkin isotherms, and their constants were determined. Using the linear correlation coefficients showed that the Langmuir isotherm best fits the AG adsorption data on PANI NT salt/silica composite. The experimental data were fitted into the following kinetic models: pseudo-first-order, pseudo-second-order, and the intraparticle diffusion model. It was observed that the pseudo-second-order kinetic model described the adsorption process better than any other kinetic models. The results obtained indicate that PANI NT salt/silica composite could be employed as a much more efficient adsorbent than the conventional PANI salt/silica composite for dye removal from water.

In this work, we used carbon nanotubes (CNTs) as a support for synthesis, size control, and morphology of magnesium oxide using the precipitation method. The morphology of MgO nanoparticles varies by changing the weight percent of carbon nanotubes in the solution. Experimental results indicate that, at optimum condition in a mixture of materials, the surface of purified CNTs is covered by MgO nanoparticles completely. The purified CNTs and MgO/CNTs nanorods had average diameters of about 35 and 65 nm, respectively, and their length was in the order of a few micrometers. The structure of CNTs and MgO/CNTs nanopowders has been characterized by analyzing the X-ray diffraction pattern, Fourier transform infrared spectra, and scanning electron microscopy images.