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首页> 外文期刊>Environmental Science & Technology >Bifunctionalized Mesoporous Silicas for Cr(VI) Reduction and Concomitant Cr(lll) Immobilization
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Bifunctionalized Mesoporous Silicas for Cr(VI) Reduction and Concomitant Cr(lll) Immobilization

机译：双官能化介孔二氧化硅，用于还原Cr（VI）和固定Cr（III）

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摘要

Surfactant-templated thiol-functionalized mesoporous silica adsorbents have been prepared by cocondensation of mercaptopropyltrimethoxysilane and tetraethoxysilane 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/SO_3H). 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(lll) 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(lll) binding to sulfonate groups, which was best achieved at pH 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(lll) immobilization, which was only attained with materials containing already some sulfonic acid groups priorto contacting Cr(VI) solutions. Redoxspeciation of sulfur and chromium species was analyzed by X-ray photoelectron spectroscopy (XPS) and used to supportthe proposed mechanism.
机译：在巯基丙基三甲氧基硅烷和四乙氧基硅烷在十六烷基三甲基溴化铵的存在下，通过缩合制备表面活性剂为模板的巯基官能化介孔二氧化硅吸附剂，然后将其部分氧化，得到同时包含巯基和磺酸部分的双官能化材料（MCM-41-SH / SO_3H） 。根据还原吸附机理，将所得有机-无机杂化体用于铬的吸收，该机理涉及通过硫醇基还原Cr（VI）并将Cr（III）固定在磺酸基团上。这些过程受到pH的强烈影响，有效螯合铬的最佳条件是由于pH值足够低以确保Cr（VI）的定量还原，而pH值又太低而无法使Cr（III）与磺酸盐基团结合，这导致了铬的螯合。在pH 2-3时最佳。还讨论了固溶比和-SH和-SO3H基团相对量的影响。即使通过硫醇基还原Cr（VI）导致形成磺酸部分，其含量也不足以确保定量固定Cr（III），只有在接触Cr（ VI）解决方案。通过X射线光电子能谱（XPS）分析了硫和铬物种的氧化还原形态，并用于支持所提出的机理。

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