Robust and stretchable dynamic cellulose-based complex hydrogels and their dye adsorption performance.

Dye-contaminated wastewater poses severe environmental and health risks. To address this challenge, this study developed a novel composite hydrogel based on oxidized carboxymethyl cellulose (OCMC). OCMC was first synthesized via sodium periodate oxidation of carboxymethyl cellulose and subsequently cross-linked with gelatin (GEL) and alkali lignin (AL) to fabricate OCMC/AL/GEL composite hydrogels. The composite hydrogel has a dual-network structure stabilized by dynamic imine and hydrogen bonds. It delivers a tensile strength of 239 kPa, stretchability of 327%, exceptional fatigue resistance (100 continuous stretching cycles without failure), and self-healing ability. The optimal adsorption conditions for methylene blue (MB) were determined as pH 6.0, an adsorbent dosage of 0.02 g, and a temperature of 30 °C, under which the adsorption capacity reached 103.33 mg/g within 12 h. Furthermore, competitive adsorption experiments in mixed-dye systems demonstrated the hydrogel's preferential selectivity for cationic dyes. By leveraging structural optimization and synergistic interactions, this work significantly enhances both the adsorption capacity and selectivity for MB while ensuring recyclability. These findings suggest that the developed OCMC/GEL/AL hydrogel is a promising and efficient adsorbent for advanced dye wastewater treatment.