Electrocatalytic Oxidation of 1-Butyl-3-Methylimidazolium Chloride: Effect of the Electrode Material

Aqueous process diluted solutions containing ionic liquids (ILs) are a challenge for water treatment as many ionic liquids are not biodegradable and hazardous for the environment. As an advanced oxidation process electrochemical depletion of the 1-butyl-3-methylimidazolium chloride (IM14Cl) dissolved in water was studied using dimensionally stable anodes (IrPt, IrO2, PbO2) and boron-doped diamond (BDD). Cyclic voltammetry demonstrated that electrochemical oxidation of the IM14(+) mainly occurred indirectly via center dot OH and by other chemical entities such as active chlorine species. Next, ionic liquid oxidation was carried out galvanostatically in the potential region of water discharge. The conventional electrodes (IrPt, IrO2) were ineffective for the removal of IM14Cl. As the IrO2 anode surface was deactivated by organic intermediates generated in this process, IM14Cl degradation was not complete and COD removal was very low (19%). Effective electrochemical oxidation was achieved at "non-active" electrodes like PbO2 and BDD. At the lowest used current density COD removal was 60% and 84% for PbO2 and BDD respectively. To better understanding the mechanism of IL electrooxidation by-products were identified by GC-MS technique. The results suggested that the electrolysis at "active" and "non-active" electrode materials led to the different distribution of products, due to different mechanism of IL degradation.