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Structural Variety and Adsorptive Properties of Mesoporous Silicas with Immobilized Oligosaccharide Groups

机译:固定化寡糖基介孔二氧化硅的结构多样性和吸附性能

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摘要

In this research, we report on the synthesis of mesoporous silicas with various quantities of immobilized oligosaccharide groups and different pore ordering degree. The hydrothermal co-condensation of tetraethyl orthosilicate and β-cyclodextrin-containing organosilane in the presence of cetyltrimethylammonium bromide template was employed. The purpose of this investigation was to show the opportunity of increasing β-cyclodextrin content in silica matrix by changing the molar ratio of initial reagents during organosilane synthesis and to determine whether the enhancing of immobilized groups on the surface influences on model aromatic compound adsorption from water. It was prepared several β-cyclodextrin-organosilanes by modification of (3-aminopropyl)triethoxysilane with oligosaccharide (the molar composition of reaction mixtures were 1:1, 3:1, and 5:1) with using N,N′-carbonyldiimidazole as linking agent. Three types of MCM-41 materials were obtained with 0.018, 0.072, and 0.095 mmol g−1 β-cyclodextrin-group loading according to chemical analysis of silicas. The IR spectroscopy and potentiometric titration were also performed to confirm the presence of functional groups in the silica matrix. Nitrogen sorptometry experiments exhibited the decrease of high surface area (from 812 to 457 m2 g−1) and the average pore diameter (from 1.06 to 0.60 cm3 g−1) of synthesized silicas with increasing of immobilized oligosaccharide groups. The influence of β-cyclodextrin-organosilane presence on the forming of hexagonally arranged porous structure of silicas was evaluated by X-ray diffraction and TEM analyses. As the loading of oligosaccharide groups increases in obtained silicas, the (100) reflex in diffraction patterns is even less intense and broader, denoting the decrease of long-range pore ordering. Adsorption experiments were carried out to study the effect of β-cyclodextrin groups’ attendance in silica matrix on benzene uptakes from aqueous solutions. Experimental kinetic curves of benzene adsorption on synthesized silicas were compared with theoretical models of Lagergren and Ho-McKay for pseudo-first and pseudo-second-order processes. Langmuir and Freundlich isotherm models were used to evaluate adsorption processes and parameters. Obtained β-cyclodextrin-containing MCM-41 silicas demonstrate adsorption level performance of known samples and could be very promising for benzene uptakes from aqueous solutions in water treatment processes.
机译:在这项研究中,我们报道了具有不同数量的固定寡糖基团和不同孔有序度的介孔二氧化硅的合成。在十六烷基三甲基溴化铵模板存在下,使用原硅酸四乙酯和含β-环糊精的有机硅烷进行水热共缩合。这项研究的目的是通过改变有机硅烷合成过程中初始试剂的摩尔比来显示增加二氧化硅基质中β-环糊精含量的机会,并确定表面固定化基团的增强是否影响模型芳香化合物从水中的吸附。通过用N,N'-羰基二咪唑为低聚糖对(3-氨基丙基)三乙氧基硅烷进行寡糖修饰(反应混合物的摩尔组成为1:1、3:1和5:1),制备了几种β-环糊精-有机硅烷。链接代理。根据二氧化硅的化学分析,获得了三种类型的MCM-41材料,分别具有0.018、0.072和0.095 mmol g -1 β-环糊精基团负载量。还进行了红外光谱和电位滴定,以确认二氧化硅基质中存在官能团。氮吸附实验显示出高表面积的减少(从812降至457 m 2 g -1 )和平均孔径(从1.06降至0.60 cm 3 g -1 )随着固定化寡糖基团的增加而合成。通过X射线衍射和TEM分析评估了β-环糊精-有机硅烷的存在对六边形排列的二氧化硅多孔结构形成的影响。随着所获得的二氧化硅中寡糖基团的负载增加,衍射图谱中的(100)反射甚至更弱且更宽,表明远程孔径有序性降低。进行吸附实验以研究β-环糊精基团在二氧化硅基质中的存在对水溶液中苯吸收的影响。将苯吸附在合成二氧化硅上的实验动力学曲线与Lagergren和Ho-McKay的拟一阶和拟二阶过程的理论模型进行了比较。用Langmuir和Freundlich等温线模型评估吸附过程和参数。所获得的含β-环糊精的MCM-41二氧化硅具有已知样品的吸附水平性能,对于水处理过程中水溶液中的苯吸收很有希望。

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