Cellulose based hierarchically structured anion-exchange fiber for efficient dye adsorption

Ion-exchange fiber has been widely used as a conventional adsorbent for water purification, but its base material, the petroleum, does not comply with the current trend of environmental protection. The synthesis of functional materials from natural resources attracts intensive interest. Cotton lint fiber is a natural cellulose based hollow fiber, which has a unique advantage in ion-exchange process. Herein, for the first time, a cationic design for the cotton lint fiber was carried out in a simple two-step strategy. The cellulose based anion-exchange fiber (CAF) showed well-preserved fibrous macrostructure and cellulose nanofibril structure. And the ideal cationic group content (133.26 mmol·100 g −1 ) of it indicates the successful combination of structural and functional properties, which are the responsible for its excellent adsorption efficiency that includes the high adsorption capacity (above 1300 mg g −1 ), rapid adsorption rate (90% of its equilibrium uptake within 6 min at the initial concentration of 300 mg L −1 ), perfect solid/liquid separation property, and good recyclability (> 95%) for congo red. Additionally, the adsorption mechanism can be attributed to the synergistic effect of electrostatic attraction, hydrogen bonding, and van der Waals force, which was explained by the employment of classical adsorption models and advanced double layer statistical physical model. The results show that this functionalized biomaterial is an ideal candidate to replace the conventional anion-exchange fiber. This work not only revolutionizes the application of natural plant fiber, but also provides a cost-effective and simple strategy for the utilization of cellulose.