Synergistic Integration of Clay Mineral and Microcrystalline Cellulose Into Robust Aerogels for Superior Congo Red Decontamination

The treatment of wastewater containing refractory anionic dyes remains a significant environmental challenge, driving the need for adsorbents that combine high capacity, rapid kinetics, and excellent reusability. Here, we report a sustainable strategy for fabricating three‐dimensional porous hybrid aerogels (MPES and MPEA) via a sol–gel process coupled with freeze‐drying. Microcrystalline cellulose (MCC) and natural clay minerals (sepiolite or attapulgite) are cross‐linked with epichlorohydrin (ECH) and functionalized by polyethyleneimine (PEI) to construct a robust biomass‐based adsorbent. The optimized MPEA‐2 aerogel exhibits exceptional adsorption performance for the anionic dye Congo Red (CR), achieving a maximum capacity of 5337.54 mg g −1 at 308 K. Kinetic and isotherm studies revealed that the adsorption process follows the pseudo‐second‐order and Langmuir models, indicating chemisorption‐driven monolayer adsorption. The high efficiency is attributed to a synergistic mechanism dominated by electrostatic attraction between protonated amine groups from PEI and sulfonate groups of CR, assisted by hydrogen bonding, pore filling, and ion exchange facilitated by the clay mineral components. The aerogel demonstrates excellent regenerability and long‐term stability, retaining > 80% and ~70% of its initial capacity after five and eight consecutive cycles, respectively. This work provides a feasible route to design efficient biomass‐based adsorbents for dye wastewater purification.