Preparation, Characterization, Application and Structure Evolution of Attapulgite: From Nanorods to Nanosheets

Attapulgite (AT) nanorods are generally regarded as one-dimensional materials and have been widely used in many fields. Two-dimensional (2D) AT nanomaterials have remained quite rare due to the difficulty of assembling from one-dimensional nanorods. Herein, we have prepared a novel type of single-layered 2D palmate AT nanosheets (AT-NS) with uniform size by a solvothermal synthesis process. The morphology and structure of the obtained 2D nanosheets were characterized by SEM, TEM, AFM, XRD, FTIR, and XPS. It was found that the AT nanosheets have a mean thickness in the range of 30–50 nm, and the length and width are in the range of 30 nm-2 μm. The structure evolution from AT nanorods to nanosheets were systematically studied and revealed. It was shown that the amination of AT and the introduction of trivalent iron ions (Fe3+) ions into the AT materials play key roles in the formation of AT-NS. The AT nanorods are connected each other by the AT-NH2 groups coupling with the Fe3+ ions on the AT surface. More importantly, the Fe3+ substitute the Al3+, Mg2+ in AT mainly along the (1 1 0) planes. Therefore, the coordination of trivalent iron ions with amino groups occurs on the AT (1 1 0) plane. As a result, multiple nanorods are connected side by side to form the 2D nanosheets in a palmate shape. It is believed that the special morphology and structure of the 2D AT-NS material may bring some outstanding performance, which makes it have potential important application such as the demulsification of crude oil-in-water emulsion. In addition, the confined 2D assembling methodology offers us a new way to design and prepare novel materials with 2D structure.