Eco-friendly and mechanically stable carboxymethylated cellulose nanofibril and polyvinyl alcohol aerogel for effective methylene blue adsorption from water

Abstract

An eco-friendly and mechanically stable carboxymethylated cellulose nanofibril/polyvinyl alcohol/citric acid (CMCNF/PVA/CA) aerogel (CPCA) was prepared for efficient methylene blue (MB) adsorption using freeze-drying and thermal esterification. The novelty of this work is in achieving a balanced combination of high adsorption performance, mechanical stability, wet durability, and regeneration capability through the integration of CMCNF, PVA reinforcement, and CA crosslinking. The incorporation of PVA transformed the fragile CMCNF aerogel structure into a stable interconnected porous network with enhanced mechanical strength and adsorption-site accessibility. Among the prepared aerogels, CPCA-20 exhibited the optimum performance with a compressive strength of ∼1.41 MPa at 75% strain and a shape recovery of 75%. The aerogel showed a maximum monolayer adsorption capacity of 251.32 mg/g with optimum adsorption at pH 6–9, 1 g/L adsorbent dosage, 180 min contact time, and 298 K. Adsorption kinetics followed the pseudo-second-order model (PSO), while Freundlich and D–R analyses indicated heterogeneous multilayer physisorption dominated by electrostatic attraction and hydrogen bonding. The aerogel retained >95% regeneration efficiency after five cycles, demonstrating strong potential as a sustainable and recyclable adsorbent for wastewater treatment.