Iron-Based Lewis/Brønsted Deep Eutectic Solvents for the Hydrolysis of Nylon-6,6

Approximately one-third of the global nylon production is accounted for by polyamide 6,6 (PA 66), with an annual output of 2.5 million tonnes. Despite its limited biodegradability, few end-of-life recycling strategies have been developed for PA 66. In this work, PA 66 is quantitatively depolymerized into its monomers: adipic acid and hexamethylenediamine (recovered as diammonium dichloride) using a naturally abundant iron-based Lewis/Brønsted acidic deep eutectic solvents (LBDESs) at 180 °C in 5 h. After optimization of the reaction conditions and work-up procedure, the overall monomer recovery yield exceeds 85%. The process is effective not only for virgin PA 66 in pellet and fiber forms but also with real post-consumer 100% nylon hosiery. Furthermore, environmental performance metrics for this method were evaluated and compared to previously reported depolymerization processes, indicating that the present approach is competitive.