Depolymerization of poly(ethylene terephthalate) waste with biomass-waste derived recyclable heterogeneous catalyst

Poly(ethylene terephthalate) (PET) is one of the most widely used polymeric materials in chemical industry representing about 13% of the world's production. With the exponentially increasing consumption of plastics combined with its non-biodegradability, the accumulation of plastic waste in the environment rises steeply and its recycling has attracted enormous attention among researchers in recent years. In this present work, we describe bamboo leaf ash (BLA) as a bio-waste derived recyclable heterogeneous catalyst for the depolymerization of waste PET. The prepared catalyst was characterized by FT-IR, XRD, SEM, TEM, EDX, TGA and BET analyses to assess its morphology and composition. Postconsumer PET bottles were shredded and processed with 20 wt% BLA and 16 equivalents of ethylene glycol (EG) at 190 °C for 3.5 h under atmospheric pressure to give recrystallized bis(2-hydroxyethyl) terephthalate (BHET) monomer in 83% yield. The catalyst can be reused for four catalytic cycles and the residual EG was recovered for subsequent catalytic reactions. Excellent activity, cost-free, environmental-friendliness and ease of preparation, handling and reusability of the catalyst with simple work-up procedure are the notable advantages of this protocol.