Removal of Chromium(VI) from Aqueous Solution Using Persimmon Tannin Gel and Subsequent Recovery as Chromium(III)

Abstract

This study herein was investigated the removal of chromium(VI) from an aqueous solution using persimmon tannin gel and its subsequent recovery as chromium(III). At pH 2, Cr(VI) was effectively adsorbed (~80% adsorption) and <20% of this Cr(VI) was reduced to Cr(III) in the solution. More specifically, all adsorbed Cr(VI) from a 50 ppm solution was reduced to Cr(III) on the persimmon gel within 10 min. Although desorption of the Cr(III) species was challenging at 30˚C, it was increased upon increasing the temperature and was quantitatively desorbed in the presence of 1 M hydrochloric acid under reflux. In addition, although the quantity of retained Cr(VI) on the tannin gel increased upon increasing the chromium concentration of the original aqueous solution, all the desorbed chromium was successfully reduced to Cr(III). Finally, Cr(VI) removal and recovery as Cr(III) was repeated effectively 8 times using the same persimmon tannin gel sample, thus demonstrating the recyclability of this system.