The accumulation of end-of-life polyamide 6 (PA6) fishing nets in marine environments poses a serious ecological and waste management challenge1. Recent advances in chemical recycling through solvolysis have opened new avenues for recovering high-value monomers such as ε-caprolactam from polyamide waste streams, thus supporting circular economy principles and the production of next-generation materials. In this investigation, a deep eutectic solvent (DES) composed of choline chloride and diethanolamine (ChCl:DEA) at different molar ratios is employed as both reaction medium and nucleophilic agent for the depolymerization of PA6 sourced from marine waste2.
The study systematically explores the solvolysis process under moderate thermal conditions (170–210 °C), focusing on the optimization of reaction parameters such as molar composition, catalyst loading, and temperature, using a statistical experimental design. The catalytic role of 4-(dimethylamino)pyridine (DMAP) is evaluated for its potential to enhance depolymerization kinetics and product selectivity. Structural changes in the polymer matrix are monitored via attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR), while depolymerization efficiency is assessed through gravimetric analysis. The ChCl:DEA DES demonstrated a robust performance, promoting extensive amide bond cleavage through its dual-function behavior and serving both as a polar solvent and as a reactive nucleophile capable of exerting an aminolytic attack on the polymer backbone.
Previous studies have shown the effectiveness of DES and related ionic media in the chemical depolymerization of polyesters and polyamides due to their unique hydrogen-bonding and catalytic properties (Badia et al., 2024; Sert et al., 2021). The present work contributes to this growing body of knowledge by demonstrating the applicability of ChCl:DEA for the efficient recycling of real-world marine PA6 waste under relatively mild and scalable conditions.
This approach highlights a promising route for upcycling problematic marine plastics into valuable chemical feedstocks, reducing the environmental impact of discarded fishing gear while enabling the development of sustainable materials from secondary raw resources.
