Synergistic design of thermoresponsive interpenetrating network hydrogels for efficient and dynamic Pb(II) adsorption

Thermo-responsive materials represent a novel class of functional materials capable of reversible swelling, contraction, or phase transition in response to environmental temperature changes, demonstrating vast potential in environmental remediation. This study successfully synthesized a composite hydrogel with interpenetrating network structure, using sodium alginate (SA) and sodium carboxymethyl cellulose (CMC) as the matrix, and incorporating the thermo-sensitive polymer poly(N-isopropylacrylamide) (PNIPAM). The SCP composite gel enables controlled adsorption and release of Pb(II) through temperature-dependent regulation of surface hydrophilicity. At lower temperatures, hydrophilic groups are exposed on the material surface, resulting in a high Pb(II) adsorption capacity of up to 311 mg g⁻¹. When the temperature exceeds the lower critical solution temperature (LCST), a conformational transition occurs, leading to the concealment of hydrophilic groups and subsequent release of adsorbed Pb(II). This tunable approach ensures superior regeneration performance of the material. The reliability of the experimental data was further validated by fitting with isothermal adsorption models and kinetic models. This study has shown that SCP composite hydrogel is a cost-effective and highly efficient adsorbent for Pb(II), holding significant application value in the treatment of heavy metal wastewater.