Bifunctionalized mesoporous silicas for Cr(VI) reduction and concomitant Cr(III) immobilization
Bifunctionalized mesoporous silicas for Cr(VI) reduction and concomitant Cr(III) immobilization
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DOI：
10.1021/es800677b
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发表时间：
2008-09-15
影响因子：
11.4
通讯作者：
Walcarius, Alain
中科院分区：
文献类型：
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作者：
Shevchenko, Nataliya;Zaitsev, Vladimir;Walcarius, Alain
以巯基丙基三甲氧基硅烷和四乙氧基硅烷为原料，在十六烷基三甲基溴化铵存在下共缩合，再经部分氧化得到含巯基和磺酸基的双功能化材料（MCM-41-SH/SO 3 H），制备了以表面活性剂为模板的巯基功能化介孔氧化硅吸附剂。将所得的有机-无机杂化物应用于根据还原-吸附机理吸收铬物种，所述还原-吸附机理涉及通过硫醇基团还原Cr（VI）和将Cr（III）固定到磺酸部分上。这些过程受到pH值的强烈影响，有效的铬螯合的最佳条件来自pH值之间的妥协，pH值足够低，以确保Cr（VI）的定量还原，而不是太低，以使Cr（III）结合到磺酸盐基团，这是最好的实现atpH 2-3。还讨论了固液比和-SH和-SO 3 H基团的相对量的影响。即使Cr（VI）通过硫醇基团还原导致形成磺酸部分，其含量也不足以确保定量的Cr（III）固定，这仅在接触Cr（VI）溶液之前用已经含有一些磺酸基团的材料获得。氧化还原形态的硫和铬物种进行了分析，通过X射线光电子能谱（XPS）和用于支持所提出的机制。
Surfactant-templated thiol-functionalized mesoporous silica adsorbents; have been prepared by cocondensation of mercaptopropyltrimethoxysilane and tetra ethoxysilane in the presence of cetyltrimethylammonium bromide, which were then partially oxidized to get bifunctionalized materials containing both thiol and sulfonic acid moieties (MCM-41-SH/SO3H). The resulting organic-inorganic hybrid was applied to the uptake of chromium species according to a reduction-sorption mechanism involving reduction of Cr(VI) by thiol groups and immobilization of Cr(Ill) onto sulfonic acid moieties. These processes were strongly affected by pH,and the optimal conditions for effective chromium sequestration resulted from a compromise between pH values low enough to ensure quantitative reduction of Cr(VI) and not too low to enable Cr(III) binding to sulfonate groups, which was best achieved atpH 2-3. The effect of the solid-to-solution ratio and the relative amounts of -SH and -SO3H groups was also discussed. Even if Cr(VI) reduction by thiol groups resulted in the formation of sulfonic acid moieties, their content was not high enough to ensure quantitative Cr(III) immobilization, which was only attained with materials containing already some sulfonic acid groups prior to contacting Cr(VI) solutions. Redox speciation of sulfur and chromium species was analyzed by X-ray photolelectron spectroscopy (XPS) and used to support the proposed mechanism.