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 hydrogel (La(OH)3@SA/PAM) is fabricated by in situ growth of La(OH)3 on the inner walls of alginate/polyacrylamide networks. Due to the binding sites provided by alginate, La(OH)3 nanoparticles are immobilized with homogenous distribution in the hydrogel support. Notably, La(OH)3@SA/PAM exhibits extremely high adsorption capacities of 1610.34 mg/g, 993.29 mg/g and 3000.08 mg/g for methylene blue, crystal violet, and malachite green, respectively, and the adsorption process fits 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...