Chitosan capped Au@Pd@Ag trimetallic nanoparticles: Synthesis, stability, capping action and adsorbing activities

Chitosan is a biodegradable, biocompatible, and nontoxic biopolymer. Au@Pd@Ag NPs were prepared with chitosan as a capping agent. Chitosan-Pd²⁺ and chitosan-Ag⁺ complexes reduced on the surface of AuNPs. The ninhydrin was used to detect the presence of the chitosan amino group on the surface of Au@Pd@Ag NPs. Viscosity data revealed that the capped chitosan was stable with ageing time. Chitosan capped Au@Pd@Ag was used as an adsorbent to the removal of acid orange 7 from wastewater. The maximum adsorption efficiency (q⁰_max = 71.42 mg/g with regression: R² = 0.996) was calculated from Langmuir adsorption isotherm to the adsorption of dye. The acid orange 7 dye removal followed the pseudo-second-order kinetics with a high correlation (R² = 0.999). Maximum adsorption (90%) was observed in acidic pH (= 6.0). The oxidative dissolution of Ag⁺ ions from the surface of chitosan capped Au@Pd@Ag NPs were very slow and depend on the pH.