Eco-engineered sodium alginate-bentonite-Fe-ATA aerogels with tunable crosslinking for high-efficiency cationic dye...

Sodium alginate (SA)-based aerogels and MOF materials have been well documented for dye removal, yet both materials face fundamental limitations that hinder their use in real waters. SA exhibits a single type of adsorption site in its unmodified form, whereas MOFs suffer structural damage upon long-term exposure to aqueous environments. To address these issues, this study achieved the in-situ growth of a metal (Fe³⁺)-ligand (2-aminoterephthalic acid (ATA)) coordination network within the sodium alginate gel scaffold, thereby maximizing the synergistic adsorption advantages of SA aerogels and Fe-MOF. The material was further reinforced with bentonite (BNT) to enhance mechanical rigidity and diversified functionality for improved dye capture. Sequential crosslinking of the SA-BNT mixture with Fe³⁺ and ATA, respectively, yielded a doubly crosslinked aerogel (DCL-aerogel) containing in situ-formed metal-ligand coordination bonds. DCL-aerogel exhibits superior dye adsorption performance, with maximum adsorption capacities for methylene blue (MB) and crystal violet (CV) reaching 1317 and 1334 mg/g, respectively. The adsorption behavior followed the Langmuir isotherm and the pseudo-second-order kinetic model, achieving equilibrium within 120 min and maintaining strong stability over a wide pH range (2-12). The DCL-aerogel exhibited excellent dye removal efficiency, structural stability, and chemical adaptability, demonstrating its great potential as a sustainable bio-MOF hybrid adsorbent for wastewater purification.