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.
Rollo et al. (Sun,) studied this question.