Ethanolysis of PLA using ChCl/Zn(OAc)2 deep eutectic solvent for sustainable ethyl lactate production

Polylactic acid (PLA) is a biodegradable polyester generated from renewable materials and is progressively utilised as a sustainable substitute for traditional polymers. However, limitations in mechanical recycling create a need for efficient chemical recycling routes that support a circular plastics economy. The ethanolysis of PLA to produce ethyl lactate (EtLa), a valuable green solvent, presents an appealing method for upcycling PLA waste. This study reports for the first time the depolymerisation of PLA into EtLa using a deep eutectic solvent (DES) composed of choline chloride (ChCl) and zinc acetate (Zn(OAc) 2 ) at a 1:1 molar ratio. The catalytic performance of Zn(OAc) 2 in its anhydrous and dihydrate forms are compared. Reactions were conducted between 80 and 140 °C. The anhydrous Zn(OAc) 2 DES consistently delivered faster depolymerisation ( E a = 23.3 ± 7 kJ·mol -1 ) relative to the dihydrate analogue ( E a = 31.6 ± 2 kJ·mol -1 ), demonstrating a higher catalytic activity. Complete PLA conversion and 94% EtLa yield were achieved at 140 °C and 8 h. DES recyclability was also evaluated. The efficiency of the DES catalytic system was further demonstrated by obtaining EtLa from actual post-consumer PLA waste (PLA toy, disposable cup and 3D-printing filament). Overall, this work demonstrates a greener and efficient method for producing EtLa from waste PLA.