Selective Depolymerization of Poly(ethylene terephthalate) in Mixed Plastic Waste Using Magnetically Recoverable nZVI Catalyst
Priyank Sinha, Sudipta Paul, Swarup Maity, Sanjib Banerjee
Abstract
The escalating global plastic waste crisis, particularly that of poly(ethylene terephthalate) (PET), necessitates innovative recycling approaches that align with the concept of a circular economy. In this study, we present an efficient and sustainable strategy for PET depolymerization via glycolysis, employing a magnetically recoverable nano zerovalent iron (nZVI) catalyst. Key reaction parameters, including the ethylene glycol (EG)/PET ratio, catalyst loading, reaction time, and temperature, were systematically optimized, achieving complete PET conversion and a bis(2-hydroxyethyl) terephthalate (BHET) yield exceeding 90%. The catalyst exhibited excellent reusability over four cycles, and its selectivity was demonstrated in mixed plastic waste systems where PET was effectively depolymerized, while bisphenol A polycarbonate (BPA-PC) remained largely unaffected. The comparison with BPA-PC highlights the specificity of the nZVI catalyst toward ester bond hydrolysis in PET, while BPA-PC, a carbonate-based polymer with a difference in structure and glycolysis reactivity, remained resistant under the same reaction conditions. Moreover, the process integrated efficient recovery and recycling of unreacted EG, further enhancing its sustainability. These findings underscore the potential of nZVI-catalyzed glycolysis as a green, economically viable solution for advanced PET recycling and waste management.