Preparation of Mg-Al Layered Double Hydroxides Ultrathin Nanosheets and Its Application in Adsorption of Methyl Orange.

In this paper, well-defined Mg-Al LDHs nanosheets with high yield are prepared by the following sequential procedures: hydrothermal preparation of Mg-Al-CO 3 2 − LDHs, followed by expanding interlayer spacing by NH₄NO₃ treatment. The results show that the concentration of the layer expansion agent (NH₄NO 3) and the exfoliation solvent play a key role in the exfoliation result. The basal spacing changed from 0.758 nm to the range of 0.758–0.895 nm when the concentration of NH₄NO₃ was increased up to 5 M, which infers that the increase of layer space is caused by the synergy of NH 4 + and NO 3 − . Among the three exfoliation solvents (formamide, N-methyl pyrrolidone and isopropyl alcohol), formamide showed the highest exfoliation effect. From the characteristic XRD patterns, the as-obtained colloidal aggregates of the exfoliated nanosheets do not show the characteristic diffractions of LDHs, while the typical peaks at 10.562 ∘ , 20.032 ∘ and 21.185 ∘ assigned to LDHs are observed after drying of the colloidal aggregates. Moreover, a transparent LDH film is also successfully prepared by coating colloidal aggregates of nanosheets on a glass substrate without using any adhesive. The stable film exhibits the strong adsorption ability of Methyl Orange. The success in obtaining well-defined Mg-Al LDHs nanosheets through the following sequential procedures was described: hydrothermal preparation of Mg-Al LDHs, expanded interlayer spacing by NH₄NO₃ treatment, and stable, transparent colloidal suspension with no solid residues after standing in formamide for 2 days. The product had strong adsorption ability. [ABSTRACT FROM AUTHOR]