Recent progress in the preparation, characterization, and applications of modified halloysite nanotubes as adsorbents for wastewater treatment

The application of halloysite nanotubes (HNTs) in water purification is attracting extensive attention because they are inexpensive raw materials with a hollow nanotubular structure in the sub-micrometer range, a large specific surface area, pore volume, pore size, and adequate hydroxyl groups on their surface, thus enhancing their ability to be modified. These modified halloysite nanotubes (m-HNTs) have been widely used for a variety of applications, including chemocatalysis, biocatalysis, antibacterial action, drug delivery, gas separation, and adsorbents for wastewater treatment. They were reported to have been produced using a variety of synthetic processes which include self-assembly/vacuum filtering, extraction, solution casting, dehydration condensation, thermal polycondensation, chemical vapor deposition, and hydrothermal carbonization. In this review, we focus on the compilation of the most recent developments in the manufacture of m-HNTs, their characterization and possible uses in wastewater treatment. Finally, we present our personal views on the opportunities and challenges of future researches involving m-HNTs, hoping to inspire more researchers into participating in this fascinating area.