Eco-friendly poly(acrylic acid)-sodium alginate nanofibrous hydrogel: A multifunctional platform for superior removal of Cu(II) and sustainable catalytic applications

A thorough cleanup of heavy metal ions in water bodies is of vital importance for the urgent requirement of clean potable water. In this study, combining the prominent structural characteristics of electrospun nanofibers and the special property of hydrogels, we developed a green strategy to construct an eco-friendly poly(acrylic acid)-sodium alginate nanofibrous hydrogels (PAA-SA NFHs) by electrospinning PAA-SA nanofibers, and followed by a facile thermal cross-linking treatment. The resultant PAA-SA NFHs with high swelling ratio, intrinsic fiber morphology, excellent stability and satisfactory mechanical performances exhibited prominent adsorption performances towards Cu²⁺ (q_m = 591.7 mg/g) and outstanding regenerability. Notably, by virtue of the synergy of porous network structure, superhydrophilicity and faster adsorption rate, such PAA-SA NFHs membrane permitted extremely high water permeation flux solely driven by gravity (up to 868.5 L m⁻² h⁻¹) and remarkable removal efficiency, when acted as a free-standing filter for the dynamic removal of Cu²⁺. Furthermore, we also demonstrated a sustainable strategy of converting the toxic Cu²⁺ pollutants to valuable Cu nanoparticles for imparting additional functionality of catalysis, and the resultant PAA-SA NFHs with uniformly distributed Cu nanoparticles possessed an excellent catalytic activity. Consequently, constructing such attractive PAA-SA NFHs will provide new insights into the design and exploitation of novel adsorbents or filters for the practical water purification, and to recycle metals (copper and potentially others) for keeping the resources sustainable.