Transformation of waste PET into a robust broad-spectrum hydrogel adsorbent via DE-RE polymerization

Hydrogel adsorbent combines the high efficiency and easy separation characteristics of traditional adsorbent, and is considered as a promising alternative in the field of water pollution treatment. However, traditional hydrogels have poor mechanical properties and are easy to break under poor adsorption conditions, making them difficult to separate and not reusable. Therefore, developing robust, high-performance hydrogels through simple and cost-effective methods remains a major challenge. In this study, we proposed a simple and economical method to prepare hydrogel by Depolymerization-Repolymerization of waste polyethylene terephthalate (PET) under the catalysis of non-volatile metal-free green ionic liquid, so as to improve the mechanical strength and performance of hydrogel and realize the green and high-value recovery of waste PET. The fracture stress of this ingeniously designed PET-based double-network hydrogel is 150 times higher than that of a single-network hydrogel. The incorporated PET fragments confer “π-π” stacking interactions and coordination on the hydrogel and are combined with other active ingredients. The synergistic effect of these components significantly promotes the high adsorption capacity for dyes such as methylene blue (411.5 mg·g⁻¹) and acriflavine hydrochloride (1224.7 mg·g⁻¹), as well as for metal ions, demonstrating a notable selective adsorption capacity for neodymium ions in mixed metal ion solutions. This broad-spectrum hydrogel adsorbent offers a promising strategy for addressing both plastic recycling and water pollution treatment simultaneously.