Highly elastic hydrophobic-associated dual-network hydrogel for efficient and reusable removal of heavy metal ions

The discharge of heavy metal ions in industrial wastewater poses serious threats to ecosystems and human health. Herein, a novel hydrophobic-associated dual-network hydrogel (PVA/PASC 16 ) was synthesized by integrating a chemically cross-linked network of acrylamide (AM), sodium acryloyl dithiocarbamate (SAD), and cetyl dimethylallyl ammonium chloride (C 16 DMAAC) with a physically cross-linked polyvinyl alcohol (PVA) crystalline network. Structural characterization​ via FT-IR, SEM, ESEM, and Cryo-SEM confirmed the dual-network architecture and hydrophobic microdomains. Rheological analysis and swelling tests demonstrated that hydrophobic interactions from C 16 DMAAC significantly enhanced elasticity, achieving a ​94.8% creep recovery​ under 5 kPa stress while suppressing swelling. Adsorption performance revealed exceptional capacities for Cu(II) (207.58 mg·g − 1 ), Pb(II) (313.72 mg·g − 1 ), and Mn(II) (154.25 mg·g − 1 ) at pH 5.25 and 500 mg·L − 1 initial metal ion concentration within 180 min. Studies on the adsorption of Cu(II) revealed that the adsorption kinetics followed the pseudo-second-order model (R² > 0.98). Furthermore, experimental data exhibited optimal agreement with the Langmuir isotherm model, further indicating that the adsorption mechanism of the hydrogel towards Cu(II) is dominated by chemisorption. Reusability tests demonstrated > 90% adsorption capacity retention after five regeneration cycles via acid/alkaline treatment, highlighting exceptional recyclability. Mechanistic studies employing SEM-EDS, ESEM, and XPS confirmed that electrostatic attraction, ion exchange, and coordinate chelation via O/S-functional groups were the primary pathways for adsorption. This research presents a reusable adsorbent with high elasticity and adsorption efficiency, presenting a sustainable strategy for the removal of heavy metals in wastewater treatment.