Advanced oxidation process for the removal of ionic liquids from water: The influence of functionalized side chains on the electrochemical degradability of imidazolium cations

Advanced oxidation processes can assist in the elimination of imidazolium-based ionic liquids (ILs) from water. With the aid of electrocatalytic degradation at a lead dioxide anode, it was shown that the degradation rate of these ILs from aqueous solutions was dependent on a change in the nature of the side chains in the cation. All the ionic liquids were efficiently oxidized within 240 min. Even the mineralization of ILs was high up to 97% depending on structure. Cyclic voltammetry indicated that ILs were oxidized indirectly by radicals generated on the anode surface. HPLC-UV and electrospray mass spectroscopy analysis suggest that ILs undergo degradation along a pathway involving intermediates produced as a result of hydroxyl radical substitution to side chain and by oxidative cleavage of the imidazolium ring. The probability of imidazolium core attack by (OH)-O-center dot radicals increased with decreasing length of the substituted side chain. (c) 2012 Elsevier B.V. All rights reserved.