School of Environmental and Chemical Engineering, Shanghai University, No.99, Shangda Road, Shanghai 200444, PR China; Center of Green Urban Mining & Industry Ecology, Shanghai University, No.99, Shangda Road, Shanghai 200444, PR China.
School of Chemistry and Physics and Centre for Materials Science, Queensland University of Technology, Brisbane, QLD 4001, Australia.
J Colloid Interface Sci. 2022 Jul;617:363-371. doi: 10.1016/j.jcis.2022.03.022. Epub 2022 Mar 7.
The lamella aggregation state of layered double hydroxides (LDHs) may affect their sorption capacity for organic compounds. The dried LDH samples (Ni/Cr LDH-FA-D and Ni/Cr LDH-HO-D) and the undried samples (Ni/Cr LDH-FA-W and Ni/Cr LDH-HO-W) were flexibly prepared by a co-precipitation method in formamide (FA) and water, respectively. The results of X-ray diffraction (XRD) and transmission electron microscope (TEM) showed that the undried LDHs were unassembled, which had no the stacking layers but had a pseudohexagonal nanosheet lamella structure. And the unassembled LDH layers can be assembled again during the dry process. Ni/Cr LDH-FA-W and Ni/Cr LDH-HO-W showed much greater adsorption capacities towards methyl orange (MO) than Ni/Cr LDH-FA-D and Ni/Cr LDH-HO-D, as well as shorter time to reach equilibrium. The maximum adsorption capacity of MO could be calculated to 806 mg/g and 740 mg/g for Ni/Cr LDH-FA-W and Ni/Cr LDH-HO-W by Langmuir-type simulation. The greater adsorption capacities of unassembled LDH could be attributed to the loosen structure and much more exposed adsorption sites. It could be concluded that unassembled LDHs were an effective and conducive preparation pathway for the exploration of the adsorption sites of LDHs.
层状双氢氧化物 (LDHs) 的片层聚集状态可能会影响其对有机化合物的吸附能力。通过共沉淀法分别在甲酰胺 (FA) 和水中灵活制备了干燥的 LDH 样品 (Ni/Cr LDH-FA-D 和 Ni/Cr LDH-HO-D) 和未干燥的样品 (Ni/Cr LDH-FA-W 和 Ni/Cr LDH-HO-W)。X 射线衍射 (XRD) 和透射电子显微镜 (TEM) 的结果表明，未干燥的 LDH 是未组装的，没有堆叠层，但具有伪六方纳米片层结构。并且未组装的 LDH 层可以在干燥过程中再次组装。Ni/Cr LDH-FA-W 和 Ni/Cr LDH-HO-W 对甲基橙 (MO) 的吸附容量比 Ni/Cr LDH-FA-D 和 Ni/Cr LDH-HO-D 大得多，达到平衡的时间也更短。通过 Langmuir 型模拟计算，Ni/Cr LDH-FA-W 和 Ni/Cr LDH-HO-W 对 MO 的最大吸附容量分别为 806mg/g 和 740mg/g。未组装 LDH 的较大吸附容量可归因于其疏松的结构和更多暴露的吸附位点。可以得出结论，未组装的 LDH 是探索 LDH 吸附位点的一种有效且有利的制备途径。
