Ferrate(VI): Green chemistry oxidant for degradation of cationic surfactant

Abstract

Iron in its familiar form exists in the +2 and +3 oxidation states, however, higher oxidation state of iron +6, ferrate(VI) ( FeVI O4 2 - ) can be obtained. The high oxidation power of ferrate(VI) can be utilized in developing cleaner ("greener") technology for remediation processes. This paper demonstrates the unique property of ferrate(VI) to degrade almost completely the cationic surfactant, cetylpyridinium chloride (C5H5N+(CH2)15CH3 · H2O Cl-, CPC). The Rate law for the oxidation of CPC by ferrate(VI) at pH 9.2 was found to be: -d[Fe(VI)]/dt = k[Fe(VI)][CPC]2. Ferrate(VI) oxidizes CPC within minutes and molar consumption of ferrate(VI) was nearly equal to the oxidized CPC. The decrease in total organic carbon (TOC) from CPC was more than 95%; suggesting mineralization of CPC to carbon dioxide. Ammonium ion was the other product of the oxidation. This is the first report in which FeVI O4 2 - ion opens the pyridine ring and mineralizes the aliphatic chain of the organic molecule giving inorganic ions. © 2005 Elsevier Ltd. All rights reserved.