Synthesis and Characterization of Nanomaterial Based on Halloysite and Hectorite Clay Minerals Covalently Bridged

Abstract

Halloysite is an aluminosilicate clay with a predominantly hollow tubular structure (HNTs) able to act as a nanocontainer for the encapsulation of several chemicals. However, HNTs possess low affinity for metal ions in their pristine form and they need to be modified for improving their adsorption capabilities. Therefore, to overcome this issue herein we report a straightforward approach for the covalent modification of the external surface of halloysite nanotubes with hectorite clay. Compared to halloysite, hectorite possesses a lamellar structure with higher cation exchange capacity. The covalent linkage between the two clays was verified by several techniques (FTIR spectroscopy, 13C CP-MAS NMR, TGA, -potential, DLS, and XRD measurements) and the morphology was imaged by TEM investigations. As proof of concept the adsorption ability of the obtained nanomaterial in comparison to pristine clays was proved using ciprofloxacin and silver ions chosen as models for their different chemical characteristics.