Pyrolysis of pharmaceuticals as a novel means of disposal and material recovery from waste for a circular economy

Abstract

In this study, pyrolysis is suggested as an environmentally and economically sustainable treatment for pharmaceutical waste within the context of circular economy. Low temperature pyrolysis was conducted on immediate release tablets containing 500 mg paracetamol, with the liquid and gas products analyzed using GC-MS (gas chromatography-mass spectroscopy). The pyrolytic behavior of the pharmaceutical product was studied through kinetic and thermodynamic analysis. The data obtained by thermogravimetric analysis (TGA) were used to estimate the activation energy (E) and the pre-exponential factor (A) through isoconversional models of Kissenger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO), and The thermodynamic parameters were determined. The average E values for the pyrolysis of the drug product using KAS and FWO methods were found to be 125.9 and 128.8 kJ.mol−1, respectively. The GC-MS results showed that the most abundant component of the pyrolysis liquid was the active pharmaceutical ingredient (paracetamol), along with other compounds, including long-chain alkanes and acids while the pyrolysis gas consisted mainly of light hydrocarbons, including CO, CO2, CH4, and ethylene. Both the gaseous and liquid pyrolysis products may be repurposed, as the active pharmaceutical ingredient (API) may be recycled to produce new tablets, and the other compounds may be utilized as fuel or chemical feedstock.