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.