Facile Surface‐Modified Cellulose Nanocrystal for Adsorption of Methylene Blue Dye

Water pollution is a critical global crisis. As water sources for drinking and agriculture rapidly decline, urgent research is underway to develop advanced absorbent materials to improve wastewater treatment efficiency. This work aimed to functionalize cellulose nanocrystals (CNCs) with butyric acid to adsorb methylene blue dye. The resulting material, CNC‐B, was analyzed using FTIR, XRD, AFM, SEM, BET, and Zeta potential. The effects of initial dye concentration, CNC‐B amount, contact time, pH, and temperature on dye removal efficiency were examined. Kinetics, isothermal adsorption, and thermodynamic studies further elucidated the mechanism of the process. CNC‐B removed approximately 88.25% of methylene blue at 40 mg initial concentration, pH 8, 25°C, 40 mg CNC‐B, and 25 min contact time. The kinetic data fit the pseudo‐second‐order model. Thermodynamic analysis exhibited that adsorption was spontaneous and exothermic, and became less favorable at higher temperatures. Isothermal studies confirmed monolayer adsorption on a uniform surface, consistent with the Langmuir model. These results suggest CNC‐B is a promising, versatile absorbent for efficient adsorption of cationic dyes from water.