High-Performance Flocculant from g-C₃N₄-Mediated Cross-Linking of Chitosan and Polyacrylamide for Turbid Water Treatment

Flocculation is crucial for water purification, but conventional flocculants are hampered by inefficiency and environmental concerns. This study develops a novel chitosan-polyacrylamide (CS-PAM) flocculant innovatively synthesized using graphitic carbon nitride (g-C₃N₄) as a dual-function photoinitiator and cross-linker. This facile photocatalytic approach under ambient conditions yielded a composite flocculant (CNCSPAM) with a uniquely integrated network. The optimized CNCSPAM exhibited exceptional performance in treating highly turbid wastewater, achieving over 97% turbidity removal at an ultralow dosage of 0.25 mg L⁻¹, rapid sedimentation kinetics (<2 min), vastly outperforming its individual components. It also demonstrated wide pH applicability and strong tolerance to environmental interferents. Flocculation kinetics and mechanism studies revealed that the high efficiency stems from a synergistic effect: charge neutralization by chitosan enhanced by the bridging effect of the cross-linked PAM network. This work provides a sustainable and cost-effective flocculation strategy, notable for its green synthesis, minimal dosage, and high efficacy, representing a significant advance for water treatment technologies.