In this study, a new silica gel based adsorbent was fabricated and its ability in separation and quantification of alkanes mixture was investigated. Silica gel (SiO2) is a polar absorbent which is mainly used to separate polar compounds. Also, the carbon materials such as activated carbon and recently carbon nanotube (CNTs), have been widely used for separation of nonpolar materials. Carbon nanotubes are nanosized carbon-based sorbents that have a high surface area and a large aspect ratio and are known to be stable at high temperatures. It is, therefore, conceivable to use of their unique properties in gas chromatography. In this work, a MWCNT-Silica gel nanocomposite was prepared by Sol-Gel process and it was used as stationary phase in gas chromatography for separation of alkanes mixture. In first part, ability of silica gel adsorbent was studied and then results were compared with new MWCNT-Silica gel nanocomposite. Finally, a quantitative investigation was done on a LPG sample and propane, 2-methylpropane, n-butane, 2,2-dimethylpropane, 2-methylbutane and n-pentane were measured by standard addition. تفاصيل المقالة

The separations of alcohols with hydrophilic and hydrophobic parts, and the separation of aromatic mixtures, are extremely important processes in gas and petroleum industries. Choosing an adsorbent for performing this separation is the most important part of the process. Silica gel is used as an adsorbent is various techniques such as pressure swing adsorption (PSA) and gas and liquid chromatography. Due to the polarity of silica gel, it is used for the separation of polar molecules. Carbon materials such as activated carbon and recently carbon nanotube (CNTs) are widely used for the separation of nonpolar materials. In the course of this study, a new composite was fabricated using sol-gel methods. Multiwall carbon nanotubes (non-polar carbon-based adsorbents with high surface areas) were mixed with a silica gel base (a strong polar adsorbent). The composite was then used in the separation of mixtures of both aromatic hydrocarbons and alcohols. تفاصيل المقالة

In this research, investigation of the adsorption isotherms and the effect of solution conditions such as pH and concentration of complexation of some amino acids with cobalt(II) nitrate six-hydrate upon multi-wall type carbon nanotube (CNT) were done. The adsorption capacity of complexation of amino acids onto the surface of carbon nanotube increased with the pH from acidic to alkaline. At pH = 9 the affinity order of the complexation of amino acids towards carbon nanotube is L-arginine > L-phenylalanine > L-asparagine > L-methionine > L-cysteine > glycine > L-alanine > L-valine > L-histidine. The curves have an important role in the design and optimization of the unit operations such as preservation, drying storing packaging and mixing. The adsorption equilibrium isotherms were fitted by Freundlich, Langmuir and Temkin models, but the Freundlich model is better than other models because is does not assume the surface as homogeneous with respect to adsorption energies and also the r2 value indicates the goodness of fit between the data and the isotherm. تفاصيل المقالة

Electrochemical behaviour of acetaminophen at the multi wall carbon nanotubes/titanium dioxide (MWCNT/TiO2) composite film modified glassy carbon electrode (GCE) via solvent casting method was studied. It is shown that the MWCNT/TiO2/GCE exhibits remarkable improvement in analytical response as compared to other electrodes. Comparing the responses of the MWCNT/TiO2/GCE with that obtained at the unmodified glassy carbon electrode, the peak currents were enhanced significantly by 8.5 folds (oxidation peak) and 11.0 folds (reduction peak), which showed stable response with enhanced selectivity and sensitivity. A linear calibration plot having a correlation coefficient of 0.991 was obtained in the concentration range of 0.01-0.12 mM acetaminophen. The detection limit for the detection of acetaminophen was calculated as 11.77 μM based on 3 σ/m. The method was applied in the determination of acetaminophen in commercial tablets. The recoveries of the composite modified electrode obtained were 95.2 and 96.2% for five determinations. تفاصيل المقالة