Thermal degradation of polyvinyl chloride in the presence of lead oxide: A kinetic and mechanistic investigation

Abstract

The elimination of toxic heavy metals from metallurgical wastes before its recycling to steel furnaces is essential. Lead oxide (PbO) is a major toxic heavy metal present in electric arc furnace dust (EAFD). The co-recycling of EAFD with Polyvinyl chloride (PVC) followed by water leaching allows the elimination of this material. Herein, an experimental and theoretical kinetic investigation was conducted on the thermal degradation of PVC in the presence of PbO. An inhibiting effect of PbO on the thermal degradation of PVC was observed; the onset PVC de-hydrochlorination temperature increased from 273 to 293 °C. PbO addition also increased the activation energy of PVC mass loss from 148 kJ/mol (PVC) to 173 kJ/mol (PbO-PVC) in the conversion window 5–45 %. The theoretical Density Function Theory (DFT) suggested that the intramolecular hydrogen transfer (IHT) to form H2O on PbO surface exhibited the highest energy barrier at 251.01 kJ/mol, which aligns with the experimental data. The kinetic parameters generated here can be utilised to calculate the appropriate holding temperature and time for the effective removal of PbO from waste EAFD using PVC as a chlorinating additive. This should contribute towards optimising process economics and efficiency.