Efficient Congo Red Degradation in Aqueous Solutions Using Au/Cu@Chitosan-Coated Cotton Fiber-Supported Nanocatalyst: A Promising Approach for the Removal of Contaminants of Emerging Concern

Introduction: Industrial effluents containing synthetic dyes pose serious environmental hazards, necessitating cost-effective and sustainable catalysts for wastewater treatment. Methods: Cotton fibers were first dip-coated with 1 wt % chitosan, then impregnated with aqueous Au³⁺/Cu²⁺ salts. In-situ reduction with hydrazine generated bimetallic Au/Cu nanoparticles (NPs) on the chitosan-coated cotton (Au/Cu@Chi-CC). The catalyst was characterized by SEM, XRD, and EDX to confirm nanoparticle formation, elemental composition, and morphology. Results: SEM and XRD confirmed well-dispersed, alloyed Au/Cu nanoparticles, and EDX verified the expected Au–Cu ratio. Catalytic tests showed a pseudo–first-order rate constant of 0.298 min⁻¹ for Congo Red degradation. The catalyst strips maintained over 90 % activity after three reuse cycles, requiring only a rinse with distilled water. Discussion: The alloyed Au/Cu interface promoted synergistic electron transfer, leading to markedly higher catalytic activity than monometallic systems. The high-rate constant reflects this enhancement. Excellent reusability further demonstrates the catalyst’s stability and ease of regeneration, supporting its practical applicability. Conclusion: The Au/Cu@Chi-CC nanocatalyst couples low-cost biopolymer support with bimetallic synergy, delivering rapid dye degradation and excellent recyclability. These attributes underscore its practicality as an economical, sustainable solution for removing hazardous dyes from industrial wastewater.