Toward Renewable Water Treatments: Efficient and Sustainable Cationic Cellulose Nanofiber Flocculants Derived from Rice Straw

Flocculants are essential for removing pollutants from wastewater, yet conventional organic and inorganic types often lack renewability and pose risks of secondary pollution. In this study, a cationic cellulose nanofiber (CCNF) flocculant was developed from rice straw, offering enhanced flocculation performance, sustainability, and environmental compatibility. The cellulose nanofiber was extracted and cationically modified under mild conditions. Optimized modification enhanced cationic substitution, yielding a maximum SS removal of 98.9%. CCNF maintained stable performance under both acidic and alkaline conditions and was particularly effective in removing nanoscale SS and treating actual agricultural wastewater. Moreover, cationic modification did not significantly alter the biodegradability of cellulose, with CCNF showing a weight loss similar to that of unmodified CNF after 180 days in soil. The estimated cost of CCNF-3 was approximately 1.13 yuan/g, slightly higher than conventional flocculants, but with considerable environmental benefits.