A multifunctional chitosan-anchored copper(i)oxide/zinc oxide nanoplatform for high-capacity fluoride capture in eco-intelligent water systems

Abstract

Describing the dual imperatives of environmental stewardship and water security, this study presents an innovative, phytogenic route for the fabrication of a multifunctional Cs-Cu₂O/ZnO nanocomposite (Cs-Cu₂O/ZnO NC), employing the bioactive Water Calyx Fluid (WCF) of Spathodea campanulata as a natural reducing, capping, and stabilizing agent. This green synthesis paradigm leverages the intrinsic phytoconstituents of the WCF to orchestrate the in situ nucleation and growth of Cu₂O and ZnO nanoparticles within a chitosan matrix yielding a hybrid nanostructure characterized by enhanced surface heterogeneity, high crystallinity, and robust colloidal stability. Comprehensive physicochemical characterization confirmed the successful formation of a hierarchically porous nanocomposite. The material exhibited abundant surface functional groups and strong redox activity, making it suitable for environmental remediation applications. The nanocomposite was systematically evaluated for fluoride ion sequestration from aqueous systems, with quantification conducted via the SPADNS spectrophotometric protocol. Adsorption kinetics adhered to a pseudo-second-order model, and isotherm analyses indicated multilayer chemisorption, governed by active site interactions and ion exchange dynamics. The Cs-Cu₂O/ZnO system demonstrated significant fluoride removal efficiency under environmentally benign conditions, outperforming conventional adsorbents in both capacity and reusability. This work pioneers the utilization of Spathodea campanulata Water Calyx Fluid as a sustainable nanofactory and underscores the significant potential of green-engineered hybrid nanomaterials for next-generation water purification technologies.