Abstract:
The objective of this research was to investigate the efficiency of hexavalent chromium (Cr(VI)) removal from the solution using condensed tannin gel (CT) which has a magnetic property, as the adsorbent. Magnetism of the CT was achieved by the incorporation of magnetite (Fe3O4), manganese ferrite (MnFe2O4), or cobalt ferrite (CoFe2O4) into the gels matrix. The added magnetic property was intended to ease the separation of the gel for reuse. The tested variables in the study included the adsorption equilibrium time and pH of the solution at which hexavalent chromium removal by the magnetic condensed tannin gel (MTG) reached the maximum. The studied pHs were 1.0 3.0 5.0 and 7.0. The Cr(VI) removal efficiency of the reused MTG was also investigated. Results showed that the adsorption reached an equilibrium in 120 minutes. All MTGs were able to remove more than 98 % of 1,000 mg/L Cr(VI) when the solution has the pH of 1.0. The removal efficiency of Fe3O4 -MTG was as high as 99.46%, whereas those of MnFe2O4-MTG and CoFe2O4-MTG were 98.21% and 98.38%, respectively. The removal efficiency of all MTGs was decreased as pH of the solution increased. The lowest was at pH 7.0. Separation of the MTGs after the adsorption was easily done by using a simple magnet. After rinsing with 1M HCl and DI, the separated MTGs were ready for reuse. Except for CoFe2O4-MTG, other gels can be repeatedly used for 5 adsorption cycles with no statistically significant change in Cr(VI) removal efficiency (alpha=0.05). Therefore, the addition of magnetic materials, Fe3O4 and MnFe2O4, helped increase the ability to reuse CT at least for 5 cycles with no Cr(VI) removal efficiency compromised.