Functionalization of thermo-acid activated sepiolite by amine-silane and mercapto-silane for chromium(VI) adsorption from aqueous solutions

Abstract

Chromium(VI) adsorption from aqueous solutions onto thermo-acid activated sepiolite functionalized with (3-mercaptopropyl)trimethoxy-silane and [3-(2-aminoethylamino)pro-pyl]trimethoxy-silane, was investigated. Scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric and differential thermal analysis, nitrogen adsorption-desorption, and determination of the point of zero charge were used to characterize the obtained adsorbents. It has been established that the silanes were successfully grafted on the thermo-acid activated sepiolite surfaces and that the structure of parent material was preserved during the functionalization. The adsorption of Cr(VI) onto functionalized thermo-acid activated sepiolite was tested as a function of initial pH values at 298 K. The amine functionalized thermo-acid activated sepiolite showed a higher adsorption capacity than the mercapto functionalized thermo-acid activated sepiolite at all studied initial pH values, especially at the initial pH = 2.