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21.
The effect of silica nanoparticles on the gas separation properties of ethylene vinyl acetate (EVA) copolymer containing 28% vinyl acetate has been investigated. The EVA and hybrid EVA–silica membranes were prepared via thermal phase inversion method. Silica nanoparticles prepared by hydrolysis of tetraethylorthosilicate (TEOS), through the sol–gel mechanism. The prepared membranes were characterized using FT-IR, SEM, DSC and XRD methods. FT-IR and SEM results indicated the nanoscale dispersion of silica particles in polymer matrix. As confirmed by XRD and DSC analyses, increasing the silica content enhances the amorphous regions significantly. Gas permeation of EVA–silica nanocomposite membranes with silica contents of 5, 6 and 10 wt.% was studied for N2, O2, CO2 and CH4 single gases at pressures of 4, 6 and 8 bar. The obtained results suggest a significant increase in permeability of all gases and an increase in CO2/N2 and CO2/CH4 gases selectivities upon increasing the silica content. The possible reasons for such behavior were stated and discussed. The pressure dependence of the gas permeabilities of the membranes was also investigated.  相似文献   
22.
Afiuni-Zadeh S  Guo X  Azimi G  Lankmayr E 《Talanta》2011,85(4):1835-1841
Simple and efficient microwave-assisted acid hydrolysis (MAAH) of proteins was used for rapid quantification of α-aminoadipic semialdehyde (AAS) and γ-glutamic semialdehyde (GGS) as major protein oxidation markers. The precursor amino acid residues corresponding to AAS and GGS in oxidized proteins were derivatized by reductive amination with sodium cyanoborohydride (NaCNBH3) and p-aminobenzoic acid (ABA) followed by MAAH to generate the marker derivatives AAS-ABA and GGS-ABA. The quantification was performed using electrospray ionization liquid chromatography-mass spectrometry (ESI LC-MS). The important parameters for hydrolysis were optimized, which include the temperature, the reaction time, the acid concentration and volume as well as the microwave power. Compared to the conventional acid hydrolysis of 18-24 h using 6-12 M HCl at 110 °C applied commonly in the literature and also in this work, MAAH of proteins can be completed as fast as in only 2-10 min and, additionally, with a 3-5 times higher yield of the final derivatization products. Furthermore, a better agreement between the ratio of the detected derivatization products and the theoretical yields from the studied protein has also been achieved, which indicates that MAAH may serve as a more reliable method of acid hydrolysis for this purpose than that with conventional thermal heating. The MAAH method is demonstrated to be a time-saving, reproducible and efficient technique for studying AAS and GGS as protein oxidation markers using LC-MS.  相似文献   
23.
Surface of mesocellular silica foam (MCF) was modified by grafting 3-aminopropyltriethoxysilane (APTES) to have the positive charge, and thus, to provide sites for the immobilization of H3PW12O40 (PW12). This modified-nanosized mesoporous silica (PW12-APTES@MCF) was characterized by FTIR, XRD, BET and TEM. The photoefficiency of this nanosized mesoporous toward photodegradation of six dye solutions [rhodamine B, malachite green, methylene blue, rose bengal, solophenyl red (3-BL), yellow direct 50 (CI-50)] was investigated in a photocatalytic reactor using UV lamp as a light source. The effect of various experimental parameters on the degradation performance of the process was evaluated by examining catalyst dosage, initial dye concentration and pH of the dye solution in the presence of PW12-APTES@MCF. The photocatalytic behaviors of the PW12-APTES@MCF were also compared with two mesoporous silica-supported PW12-APTES@SBA-15 and PW12-APTES@KIT-6. It indicated that the PW12-APTES@MCF had the highest photocatalytic efficiency among three mesoporous silica-supported PW12-APTES. These photocatalysts can be reused several times although they get less active.  相似文献   
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