Stable and recyclable straw cellulose-based anion exchanger for sustainable textile dyeing wastewater treatment

Biomass-derived adsorption materials from agricultural wastes, particularly crop straw, have emerged as promising candidates for water treatment owing to their abundant sources, cost-effectiveness, and renewability. Nevertheless, the inherent limitations of raw straw-suboptimal adsorption capacity and organic matter leaching risks-restrict its viability in wastewater remediation. In this study, a straw cellulose-based anion exchanger (SCAE) with enhanced adsorption performance and recyclability was fabricated through alkaline pretreatment and monochlorotriazine-mediated etherification. The di-tertiary amine-based cationic modifier enhances the functional group density on the anion exchanger， while the natural crystalline structure of cellulose maintains the structural stability of the anion exchanger. The optimal adsorption performance can be achieved using only 12.5 % of the straw mass as the modifier. The optimized SCAE retained over 95.4 % mass retention through 15 acid-base washing cycles while demonstrating 265 mg·g^-1 static adsorption capacity for simulated dye effluents. A desorption efficiency of 97 % was achieved in the adsorption-desorption cycles using a 0.25 wt% NaOH solution. The industrial applicability of SCAE was also evidenced by a 97.7 % chroma reduction in actual printing and dyeing wastewater. Remarkably, dynamic column tests revealed that 50 g SCAE could process 18.1 L simulated effluent per cycle, maintaining 95.6 % performance retention after five cycles. This strategy bridges agricultural waste recycling with advanced water purification technologies, providing a closed-loop solution for industrial dyeing wastewater.