Embedding polydopamine in keratin-based biohydrogels for efficient dye removal

Keratin-based hydrogels have shown promise as materials for wastewater remediation, yet their low surface area and poor mechanical performance hindered the practical application. To address these challenges, we developed a bowl-shaped polydopamine-loaded sponge bio-hydrogel (BPSH) with a hierarchical porous structure and high stability. The extruded keratin chains facilitated the formation of three distinct macroporous frameworks, while embedding bowl-shaped polydopamine into the bio-hydrogel significantly enhanced the hierarchical porous structure. This modification introduced various functional groups, such as hydroxyl, amino, and aromatic rings, improving the surface area, porosity, mechanical strength and adsorption capacity of the materials. The BPSH demonstrated selective adsorption of anionic dyes, particularly Congo red (CR), with a remarkable adsorption capacity (Q_m) of 2032.5, 2284.3, and 2591.9 mg/g at 30, 40, and 50 °C, respectively. The adsorption-desorption cycles were repeated three times, and the BPSH hydrogel demonstrated excellent reusability, with adsorption capacities (Q_e) of 1948.1, 1845.6, and 1784.1 mg/g for CR in the first, second, and third cycles, respectively, confirming its strong potential for repeated use in dye removal applications. This study presents a green, efficient strategy to enhance the surface area, porosity, and mechanical stability of keratin-based hydrogels, and we look forward to the widespread application of this effective adsorbent in wastewater purification.