Attapulgite: from clay minerals to functional materials

Attapulgite is a kind of natural one-dimensional nanomaterial. Attapulgite has unique nanorod-like crystals, nanochannels and reactive groups on the surface, and has been widely used in many fields including agriculture, chemical engineering, environmental protection, adsorption materials and composites. Recently, the disaggregation of the crystal bundles of attapulgite into mono-dispersed ones has been achieved, while keeping their environment-friendly property. This has changed attapulgite from clay mineral to a very interesting nanomaterial. With unique nanorods-like crystals and nanochannels, attapulgite can be used to prepare nanocomposites via the crystals and reactive groups on the surface, and also can be used to prepare hybrid materials via the nanochannels. Attapulgite is the new focus for the preparation of diverse functional materials. Thus, it is now pertinent to give an overview of the recent progress in the field. In this review, we first overview the structure and physicochemical properties of attapulgite. Subsequently, we review the progress about disaggregation of the attapulgite crystal bundles and regulation of attapulgite structures. We then focus on the development of attapulgite-based functional materials (e.g., adsorbents, colloidal materials, hybrid materials, polymer/attapulgite composites, bio-inspired materials, catalysts and energy materials) and recycling of attapulgite. In the conclusions, we summarize the progress of attapulgite-based functional materials, and the challenges in the field. Overall, this review will hopefully promote the development of attapulgite and attapulgite-based functional materials, or even the clay-based ones.