Department of Energy and Materials Engineering, Dongguk University-Seoul, Seoul, 04620, South Korea.
ICGM, Univ. Montpellier, CNRS, ENSCM, Montpellier, France.
J Environ Manage. 2021 Jan 1;277:111455. doi: 10.1016/j.jenvman.2020.111455. Epub 2020 Oct 17.
Systematic utilization of carbonated Mg-Al layered double hydroxide (LDH) nanosheets for methyl orange removal was investigated with respect to particle dimensions. LDHs with the smallest dimensions were carefully synthesized to have a small lateral size as well as high dispersibility. The other particles, with medium and large sizes, were prepared by hydrothermal treatment and urea hydrolysis to have larger sizes and higher crystallinity. According to kinetics and isotherm analyses, the smallest LDH showed efficient adsorption of methyl orange (1250 mg/g-LDH), which was remarkably higher than the adsorption by the other LDHs with larger lateral sizes. Unlike the larger lateral-sized LDHs, the small ones were shown to utilize all accessible adsorption sites on the nanosheets, generating nanoconfinement of methyl orange molecules. Transmission electron microscopy (TEM) and powder X-ray diffraction (PXRD) patterns indicated that the LDHs with lateral dimensions of ~40 nm fully utilized interlayer nanospace. Monte Carlo simulation suggested that the intercalated methyl orange was stabilized not only through electrostatic interactions with the LDH layer but also by π-π stacking between the methyl orange molecules, which is thought to be the driving force for replacement of carbonate anions.
系统地利用碳酸化镁铝层状双氢氧化物（LDH）纳米片去除甲基橙，研究了颗粒尺寸的影响。最小尺寸的 LDH 被精心合成，具有较小的横向尺寸和较高的分散性。其他具有中等和较大尺寸的颗粒则通过水热处理和尿素水解制备，以获得较大的尺寸和较高的结晶度。根据动力学和等温线分析，最小的 LDH 对甲基橙的吸附效率很高（1250 mg/g-LDH），明显高于其他横向尺寸较大的 LDH 的吸附。与较大横向尺寸的 LDH 不同，小的 LDH 被证明利用了纳米片上所有可利用的吸附位点，从而产生了甲基橙分子的纳米限域效应。透射电子显微镜（TEM）和粉末 X 射线衍射（PXRD）图谱表明，横向尺寸约为 40nm 的 LDH 充分利用了层间纳米空间。蒙特卡罗模拟表明，插层的甲基橙不仅通过与 LDH 层的静电相互作用稳定，而且通过甲基橙分子之间的π-π 堆积稳定，这被认为是取代碳酸根阴离子的驱动力。
