Badreah A Al Jahdaly, Ghada S Masaret
A sustainable approach was proposed for the preparation of Cu-La2O3 and Cu-La2O3/chitosan (CS) nanocomposites through a biomimetic method utilizing the aqueous extract of Camellia sinensis as the bioreductant and stabilizer. CS incorporation reduced particle size (8-22 nm), enhanced surface functionality, and generated a mesoporous structure with a high surface area. The Cu-La2O3/CS nanocomposite exhibited higher antioxidant activity (IC50 = 0.228 ± 0.008 mg mL-1) than Cu-La2O3 (IC50 = 0.327 ± 0.010 mg mL-1), which may be attributed to the combined contributions of the Cu-La2O3 nanostructure and chitosan functional groups. Additionally, the Cu-La2O3/CS nanocomposite achieved up to 98% crystal violet removal under the optimized experimental conditions. The adsorption process was best described by the pseudo-second-order kinetic model (R2 = 0.999) and the Langmuir isotherm model, with a maximum adsorption capacity (qmax) of 118.6 mg g-1, suggesting predominantly monolayer adsorption. Thermodynamic analysis indicated that the adsorption process was spontaneous and endothermic. The experimental findings suggest a proposed crystal violet removal mechanism involving adsorption through electrostatic interactions and hydrogen bonding, with a possible contribution from reactive oxygen species (ROS). Moreover, the Cu-La2O3/CS nanocomposite retained high crystal violet removal efficiency after five consecutive adsorption cycles, exhibiting only a slight decrease in performance. In conclusion, the green-synthesized Cu-La2O3/CS nanocomposite represents a promising multifunctional material for wastewater remediation and antioxidant applications.