Highly efficient and rapid dechlorination of polyvinyl chloride via microwave pyrolysis

Polyvinyl chloride (PVC) waste recycling is challenging due to its high chlorine content, which generates hazardous chlorinated pollutants if treated improperly. A safe and promising PVC dechlorination method is urgently needed to address this issue. Several dechlorination methods have been reported at the laboratory scale; however, each method has its downsides, and none has been proven at the commercial scale. We present, for the first time in the literature, an effective microwave pyrolysis process that can dechlorinate PVC rapidly without the requirement of a solvent/microwave absorber. High dechlorination efficiency up to 99.6% was achieved within 96 s. This process releases hydrogen chloride and generates hydrocarbon-containing liquid and a dechlorinated residue. Dielectric analysis revealed that the untreated PVC was readily heated under microwaves due to the polar chlorine group in its structure. Thermogravimetric analysis confirmed that there were two pyrolysis stages and dechlorination was achieved after the first pyrolysis stage. Fourier-transform infrared (IR) analysis showed that all the bands corresponding to the stretching of C-Cl bonds were not detected in the dechlorinated residue. All these results prove that microwave pyrolysis is a promising process for PVC dechlorination, and it could be the game changer that makes PVC recycling commercially viable.This article is part of the discussion meeting issue 'Microwave science in sustainability'.