High-Efficiency Recovery of Au (III) From Acidic Metallurgical Wastewater Using Sulfonic Acid-Functionalized UIO-67-NH2 Metal–Organic Frameworks

A robust metal–organic framework (MOF) material, UIO67-PS, was synthesized by grafting sulfonic acid groups onto the UIO67-NH 2 framework. This modification significantly enhances the electronegativity and coordination-site density on the MOF surface, enabling threefold higher Au (III) adsorption capacity (536.4 mg/g at pH 2.0 temperature 25°C and agitation speed 120 rpm) compared to pristine UIO67-NH 2 (168.4 mg/g). The material exhibits exceptional acid resistance and recyclability (91% capacity retention after three cycles). Density functional theory (DFT) calculations and X-ray photoelectron spectroscopy (XPS) analyses reveal that the adsorption mechanism is governed by synergistic electrostatic interactions and chelation, wherein electron-rich oxygen/nitrogen-containing functional groups on the adsorbent surface coordinate with metal ions via covalent bonds to form stable five-membered ring complexes. Kinetic studies confirm rapid adsorption equilibrium (< 240 min), while thermodynamic analysis indicates an endothermic, entropy-driven process. Notably, UIO67-PS demonstrates superior selectivity for Au (III) over competing ions (e.g., Zn 2+ and Cu 2+ ) in simulated e-waste leachates. Achieving removal rates as high as 80% in real metallurgical wastewater highlights its potential for practical application. This work reveals key coordination interactions, including complexation and electrostatic attraction, within a simulated e-waste leachate system containing competing ions such as copper and nickel. These insights advance the design strategies of MOFs for sustainable Au (III) recovery and provide a scalable platform for industrial wastewater treatment, contributing to environmental protection and the sustainable utilization of critical material resources.