Cationic functionalization of cellulose monoliths using a urea-choline based deep eutectic solvent and their applications

This study investigates an alternative green strategy based on non-toxic and readily biodegradable chlorocholine chloride/urea deep eutectic solvents (DESs), which act both as functionalization agents and solvents that allow for the cationization of cellulose monoliths to form novel adsorbents for removal of anionic reactive dye from water. Cellulose monolith was produced by deacetylation of cellulose acetate monolith which was fabricated via thermally induced phase separation (TIPS) method using binary solvents of DMF and 1-hexanol. Cationization of cellulose monolith was confirmed by SEM, FTIR, elemental analysis, TGA and BET surface area analysis. For the flow-through applications, the permeability and mechanical properties were also analysed in this study. The cationized cellulose monoliths were employed to remove acid red 70 dye from aqueous solutions in dynamic adsorption experiments. Results showed exceptional affinity for adsorption of acid red 70 dye due to the charge-induced adsorption aided by quaternary ammonium groups. A high adsorbed percentage of 83% could be obtained at initial concentration of 70 ppm. Moreover, the adsorbed dye could be easily desorbed. Combining their ultrafast adsorption kinetics with excellent properties of high adsorption capacity and rapid adsorption/desorption rates remained during the five consecutive cycles, the DES-modified cellulose monolith has large potential for effluent treatment applications.