Amidoxime engineering enhanced adsorption efficiency and selectivity of diaminomaleonitrile-modified chitosan for...

Efficient and selective recovery of gold ions (Au(III)) from industrial wastewater is of significant environmental and economic importance. In this study, an amidoxime-functionalized chitosan adsorbent (CS-DAMN-AO) was synthesized via a two-step modification process for the highly efficient adsorption of Au(III). Comprehensive characterization using SEM-EDS, XPS, FTIR, XRD, BET, and TGA confirmed the successful functionalization, revealing a mesoporous structure with excellent thermal stability and significant structural changes after adsorption. Batch adsorption experiments demonstrated that CS-DAMN-AO achieved an outstanding adsorption capacity of 1720.90 mg/g at 318 K, with rapid kinetics, reaching over 90 % capacity within 30 min. Kinetic, isotherm, and thermodynamic studies indicated a spontaneous endothermic adsorption process, primarily controlled by external and internal diffusion. Moreover, CS-DAMN-AO exhibited exceptional selectivity for Au(III) in the presence of competing ions (Ni(II), K(I), Li(I), Zn(II), Co(II)). Reusability tests confirmed the material's high adsorption efficiency across multiple cycles, underscoring its practical application potential. In conclusion, this study demonstrated that CS-DAMN-AO is an efficient, highly selective and reusable adsorbent, which solves the limitations of existing adsorbents in treating complex wastewater and provides a new solution for gold recovery from wastewater.