Valorisation of polyethylene terephthalate waste: An upcycling approach into a reusable CO2 liquid sorbent

Two of the most pressing environmental issues that the contemporary society is facing are the emissions of carbon dioxide and plastic pollution. Both of these concerns have far-reaching implications for the human health, contributing significantly to climate change. In this work we propose a polyethylene terephthalate (PET) plastic waste upcycling into a liquid carbon dioxide sorbent. Through our approach we chemically recycled PET into terephthalic diamides via glycolysis and successive aminolysis. Among the obtained terephthalic diamides, N,N’-bis(2-aminopropyl)terephthalamide (BAPTA) resulted promising for the formation of a stable, homogeneous liquid if combined with propylene glycol, a non-toxic and inexpensive diol. The system was characterized by differential scanning calorimetry, density, viscosity, and conductivity measurements, resulting a low-transition-temperature mixture (LTTM) with non-ionic properties. This LTTM demonstrated a CO2 capture capacity of up to 52 gCO2/kgsorbent if exposed to 1 atmosphere of carbon dioxide at 30 °C, and it maintained its capture performances over multiple absorption–desorption cycles, suggesting its practical potential. The processes involved in the work aim at maintaining mild operating conditions, solvent recovery via distillation, and waste minimization.