Dehalogenation of polychlorinated biphenyls (PCB) by Nucleofile reactants at the presence of ionic liquids and under application of microwaves

Abstract

Laboratory-scale experiments were performed in order to examine the effect of microwave field on the effectiveness of KPEG method (nucleophilic substitution of the chlorine atoms in a molecule of PCBs by alkaline polyethylene glycol PEG) in the removal of PCBs from highly contaminated mineral oils with the content of indicator congeners (No 28,52,101,53,138 and 180) above 5500 mg kg -1. Results show that the microwave field significantly increases the reaction rate and the method's effectiveness in the removal of chlorine from the molecules of PCBs. Addition of a small amount of an ionic liquid, in this case 1-butyl-3-methylimidazolium hexafluorophosphate-[bmim][PF6], significantly positively affects the results obtained under the influence of microwave field. The KPEG method enhanced by the application of microwaves could be used in practice for decontamination and recycling of PCB-containing dielectric fluids in electric capacitors and transformers. High efficiencies of the reaction were achieved even when microwaves were applied with no PEG added, only by the presence of alkaline hydroxide or by the presence of a small amount, up to ca. 2%, of an ionic liquid [bmim][PF6]. The microwave enhanced KPEG method might has some advantages for practical uses in decontamination applications. © 2011 Global NEST Printed in Greece. All rights reserved.