Rapid adsorption of Cr (VI) on modified halloysite nanotubes

The halloysite nanotubes (HNTs) were modified with the surfactant of hexadecyltrimethylammonium bromide (HDTMA) to form a new adsorbent. The modified HNTs were characterized by the FTIR spectra and thermogravimetric analysis. The results show that quaternary ammonium cations were grafted on the nanotubes surface successfully. While the modified HNTs were used as adsorbent for Cr(VI) removal from its aqueous solution, they exhibited rapid adsorption rate for chromates and approached to 90% of the maximum adsorption capacity within 5 min. The effects of pH and ionic strength on the adsorption capacity were also investigated, which showed the adsorption capacity of the adsorbent decreased significantly with the increase of ionic strength and pH. The adsorption data of Cr(VI) on the modified HNTs are well consistent with Langmuir model. The regeneration of modified HNTs could be realized by eluents and the recovered adsorbent could be used again for Cr(VI) removal.