A Bifunctional Alginate-Based Composite Hydrogel with Synergistic Pollutant Adsorption and Photocatalytic Degradation Performance

The growing dye pollution has become an urgent threat to environmental and biological safety. To meet the requirements of both dye adsorption and photocatalytic degradation in complicated wastewater environments, here, a novel La(OH)(3)-immobilized alginate/polyacrylamide composite hydro- gel (La(OH)(3)@SA/PAM) is fabricated by in situ growth of La(OH)(3) on the inner walls of alginate/polyacrylamide networks. Because of the binding sites provided by alginate, La(OH)(3) nanoparticles are immobilized with homogeneous distribution in the hydrogel support. Notably, La(OH)(3)@SA/PAM exhibits extremely high adsorption capacities of 1610.34, 993.29, and 3000.08 mg/g for methylene blue, crystal violet, and malachite green, respectively, and the adsorption process fits the Langmuir adsorption isotherm and pseudo-second-order rate equation. The H-bonding and electrostatic interactions account for the dye adsorption. Additionally, the La(OH)(3)@SA/PAM hydrogel exhibits high photodegradation efficiency against dyes under UV-light irradiation, revealing the complete elimination of the pollutants. Furthermore, the dyes adsorbed by the hydrogel can be regenerated by solution elution. These results indicate that La(OH)(3)@SA/PAM is a promising adsorption material and an effective catalyst in wastewater purification.