Efficient sequestration and reduction of hexavalent chromium with organosilica sol–gels

Abstract

Sol–gel materials prepared from organically-modified silanes are used for sequestration and reduction of Cr(VI). These sol–gels act as matrices for sequestration and reduction of Cr(VI) as well as binding of Cr(III) ions in the porous structure. Acid treated sol–gels obtained from bis[3-(trimethoxysilyl)propyl]ethylenediamine (EnTMOS) and 3-mercaptopropyltrimethoxysilane (SHTMOS) sequester and reduce Cr(VI) from an external solution. The removal of Cr(VI) from solution was monitored spectrophotometrically and the sol–gels were characterized with FTIR and TEM. The amino and thiol groups in the hybrid sol–gels play a critical role and the gels containing both these functional groups are considerably more effective at removal of Cr(VI) than those containing just one of these functional groups. Finally, the pH of the medium is also found to be an important parameter in kinetics and efficiency of removal of Cr(VI).