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SYNTHESIS AND CHARACTERIZATION OF ORDERED MESOPOROUS MCM-41 FROM NATURAL CHLORITE AND ITS APPLICATION IN METHYLENE BLUE ADSORPTION
Clays and Clay Minerals ( IF 2.2 ) Pub Date : 2021-06-11 , DOI: 10.1007/s42860-021-00119-8
Zhizeng Wang , Qinyi Zhao , Dongyun Wang , Chong Cui

Mesoporous materials have a wide range of applications in the fields of nanotechnology, biotechnology, information technology, and medicine, but historically, the resource materials used for their synthesis have been expensive. Natural silicate minerals are characterized by their abundance, low cost, and large SiO2 contents, making them an alternative silicon source for mesoporous silica. The objective of the present study was to determine the utility of natural chlorite as the source of Si for synthesizing hexagonal mesoporous silica materials (MCM-41). The natural chlorite was pretreated by acid leaching and calcination, followed by a hydrothermal reaction with cetyltrimethylammonium bromide (CTAB) as the template, and subsequent calcination to prepare MCM-41. The structures and the porosity of MCM-41 were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), 29Si magic-angle spinning solid-state nuclear magnetic resonance spectroscopy (29Si MAS NMR), and N2 adsorption–desorption measurements. The mechanism of structural evolution from natural chlorite to MCM-41 was investigated using these techniques. Calcination of chlorite results in amorphization and partial structural breakdown, while subsequent acid leaching dissolves the Mg and Al in the octahedral sheets to leave the Si–O framework as a silicon source. 29Si MAS NMR results revealed that the ratio of Q4/Q3 increased from 0.91 to 1.21 after hydrothermal synthesis of MCM-41 from leached chlorite, demonstrating more polymerization of the Si–O structure in MCM-41. The final MCM-41 products were amorphous SiO2, with a large surface area of 630 m2/g, a pore volume of 0.46 mL/g, and a narrow pore-size distribution of 2.8 nm. MCM-41 showed favorable adsorption toward methylene blue (MB) with a monolayer adsorption capacity of up to 302 mg/g, indicating potential for application in adsorption.



中文翻译:

天然亚氯酸盐有序介孔MCM-41的合成表征及其在亚甲基蓝吸附中的应用

介孔材料在纳米技术、生物技术、信息技术和医学等领域有着广泛的应用,但从历史上看,用于其合成的资源材料价格昂贵。天然硅酸盐矿物的特点是储量丰富、成本低、SiO 2含量,使它们成为介孔二氧化硅的替代硅源。本研究的目的是确定天然绿泥石作为硅源合成六方介孔二氧化硅材料 (MCM-41) 的效用。天然亚氯酸盐经过酸浸和煅烧预处理,然后以十六烷基三甲基溴化铵(CTAB)为模板进行水热反应,随后煅烧制备MCM-41。MCM-41的结构和孔隙率通过粉末X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、29 Si魔角旋转固态核磁共振光谱(29 Si MAS NMR)和 N 2吸附-解吸测量。使用这些技术研究了从天然绿泥石到 MCM-41 的结构演化机制。亚氯酸盐的煅烧导致非晶化和部分结构破坏,而随后的酸浸溶解八面体片中的镁和铝,留下 Si-O 框架作为硅源。29 Si MAS NMR 结果表明,从浸出的亚氯酸盐中水热合成 MCM-41 后,Q 4 /Q 3的比值从 0.91 增加到 1.21,表明 MCM-41 中 Si-O 结构的聚合更多。最终的 MCM-41 产品是无定形 SiO 2,具有 630 m 2的大表面积/g,孔体积为 0.46 mL/g,孔径分布窄,为 2.8 nm。MCM-41 对亚甲基蓝 (MB) 显示出良好的吸附性,单层吸附容量高达 302 mg/g,表明其在吸附方面的应用潜力。

更新日期:2021-06-13
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