Bromine addition and successive amine substitution of mesoporous ethylenesilica: Reaction, characterizations and arsenate adsorption |
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Authors: | Kojiro Nakai Yasunori Oumi Haruyuki Horie Tsuneji Sano Hideaki Yoshitake |
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Affiliation: | aDivision of Materials Science and Chemical Engineering, Graduate School of Engineering, Yokohama National University, 79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501, Japan bGraduate School of Engineering, Hiroshima University, 1-3-2 Kagamiyama, Higashi-Hiroshima 739-8511, Japan cTosoh Corporation, 4560 Kaisei-cho, Shunan 746-8501, Japan |
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Abstract: | Bromination and subsequent ethylenediamine substitution of the C C double bond in mesoporous ethylenesilica were carried out to explore the characteristics of this periodic mesoporous organosilica. The structures of the products (Br PMO and EDA–Br PMO, respectively) were analysed by IR, Br K-edge EXAFS and NMR spectroscopies, as well as X-ray diffraction and nitrogen adsorption. We showed (1) that the formulae of the two products that formed were CHBrSiO1.5]0.45CHSiO1.5]0.55 and NH2CH2CH2NHCHSiO1.5]0.05 CHBrSiO1.5]0.40CHSiO1.5]0.55, respectively, (2) that the addition of Br2 at room temperature occurred on the C C double bonds with disturbing the framework structure, (3) that IR absorption band of C C bonds that reacted with Br2 is significantly different from that of inactive C C bond, (4) that the length of the C–Br bond was considerably longer than in conventional alkyl bromides, and (5) that a large proportion of the ν(C–Br) band remained at the same position in the IR absorption spectrum after the ethylenediamine (EDA) substitution, while a new ν(C–Br) absorption also appeared. The mechanisms of these reactions are discussed at both the micro and mesoscopic levels.Arsenate adsorption on EDA–Br PMO, in which the EDA is directly bound to the “surface” of the mesopores, was compared with adsorption on EDA–Pr–PMO, which was prepared by the direct synthesis of 3-chloropropyl-functionalized mesoporous ethanesilica followed by the substitution of Cl with EDA. The strength of the adsorption, as measured with the distribution coefficient, was greater for the former adsorbent than the latter. The origin of this difference was attributed to the distance between amino group and the surface. |
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Keywords: | Periodic mesoporous organosilica Ethylenesilica Bromination Amine substitution Arsenate adsorption |
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