A thermo-kinetic investigation on the thermal degradation of polyvinyl chloride in the presence of magnetite and hematite

Abstract

Electric arc furnace dust (EAFD) which is accumulated in large amounts world-wide contains hematite (Fe2O3) and significant quantities of magnetite (Fe3O4). Waste polyvinyl chloride (PVC) also poses a great environmental threat aside to accumulated EAFD. Both of these wastes have shown a great potential for their co-thermal treatment for metal extraction, thus minimising their environmental footprint. Herein, an investigation on the thermal degradation behaviour, reaction products, thermodynamics and the decomposition kinetics of PVC and its stoichiometric mixtures with Fe3O4 and Fe2O3 was conducted using non-isothermal thermogravimetric scans. The kinetic data suggests a significant increase in the average activation energy of PVC de-hydrochlorination from 122.6 ± 24.2 kJ/mol (pure PVC) to 177.0 ± 28.0 and 199.0 ± 77.0 kJ/mol when stoichiometric quantities of Fe3O4 and Fe2O3 were mixed with PVC. The inhibiting effect of both Fe3O4 and Fe2O3 on the degradation of PVC might be assigned to the capturing of emitted gaseous HCl which is known for its catalytic effect. This result suggests that EAFDs containing both Fe3O4 (in large amounts) and Fe2O3 can have an inhibiting effect on the de-hydrochlorination of PVC resulting in longer processing times or the requirement of higher processing temperatures for achieving reasonable reaction rates.