Halloysite nanotubes and halloysite-based composites for environmental and biomedical applications

Halloysite is a natural tubular mineral with unique properties. It can be used in a various fields of industries. The aim of current review is to describe the structural properties and methods of halloysite surface modification, what led to the extension of its application. The achievements of scientists over the last 10 years indicate that halloysite is a promising material for drug delivery, as polymer filler, as matrix for photocatalysts and adsorbents for environmental and biomedical applications. Particular attention is drawn to the magnetic nanocomposites of halloysite. The composites halloysite/metal oxides are excellent adsorbents and due to their magnetic properties can be easily separated from the treated solutions by using of external magnetic field. Magnetically controlled adsorbents can be synthesized by metal oxides incorporation into the halloysite structure due to the presence of aluminol and siloxane surface groups. Such composite systems have a high adsorption capacity and can be used for effective water purification from inorganic and organic pollutants. In addition, major problems and future prospects for halloysite composites using have been identified. This review provides the latest findings from researchers, which sheds light on future halloysite studies. •The structural properties and morphology of HNTs have been discussed.•The chemical methods of halloysite modification have been analyzed.•The outer or inner surface of HNTs can be alter by additional functionalization.•The environmental and biomedical applications of HNTs have been described.