Lignin@Polypyrrole Nanoparticles Enhanced Hydrogel for Recyclable Congo Red Dye Adsorption

ABSTRACT Polypyrrole (PPy) has been widely studied for its considerable potential in adsorption applications. However, its poor dispersibility significantly limits its effectiveness. In this work, lignin nanoparticles (LNPs) were prepared by green deep eutectic solvent, and the lignin@polypyrrole nanoparticle (NLP) was constructed via the in situ polymerization of pyrrole on the surface of the LNPs, effectively addressing the problem of uneven dispersion of PPy and improving its adsorption capacity. Furthermore, polyvinyl alcohol (PVA)/gelatin hydrogels enhanced by NLP were constructed for synergistic cyclic adsorption. The tensile strength of the composite hydrogel increased by 20% to 1.21 MPa, and its adsorption capacity for Congo red reached 202.7 mg/g. The adsorption kinetics of the composite hydrogel fit the pseudo‐first‐order adsorption model, indicating that the adsorption mechanism is primarily governed by physical adsorption. With five adsorption–desorption cycles completed, the composite hydrogel exhibited a slight decline in adsorption capacity of only 8.3% compared to the initial cycle, while maintaining good structural integrity. Overall, this composite hydrogel exhibits significant potential and excellent cyclic adsorption performance for dye wastewater treatment.