A spectroscopic study on the effect of acid concentration on the physicochemical properties of calcined halloysite nanotubes

Abstract Halloysite nanotubes a naturally occurring type of clay with unique properties. This research intends to investigate of the effects of hydrochloric acid treatment on the physicochemical and pore properties of halloysite nanotubes. X-ray diffraction (XRD), field emission scanning electron microscopy (SEM), Fourier-transform infrared (FT-IR) spectroscopy, the nitrogen adsorption-desorption isotherm (BET), thermogravimetric analyses (TGA-DTA) and X-ray photoelectron spectroscopy (XPS) were used to analyze the structure of natural, calcined, and acid-treated calcined halloysite nanotubes. From the analysis of XRD, SEM, FT-IR, BET, and TGA-DTA, it was possible to infer that activation with HCl on the calcined nanotubes allowed for an increase in the specific surface area and the volume of pores while maintaining the tubular structure of these materials. Because the samples’ tubular structure was preserved, the study’s goal was to evaluate the effects of acid treatment on calcined halloysite nanotubes for use as potential adsorbents. The influence of treatment with hydrochloric acid on the structure of halloysite nanotubes calcinated at different temperatures was investigated using a surface sensitive XPS method.