Chitosan-interpenetrated metal organic framework for targeted recovery of gold from gold-electroplating wastewater

With increasing demand and the rising difficulty and cost of primary gold mining, gold recovery from industrial wastewater is becoming increasingly important. We report a chitosan interpenetrating Zr-MOF (CS@MOF-TPA) that retains chitosan-NH₂ bonds while significantly increasing the specific surface area, overcoming the trade-off between stability and functionality encountered in traditional cross-linking methods. Triazine-N/-NH₂-linkers are introduced into the MOF linker, increasing the density of N/O donor sites. CS@MOF-TPA operates within a pH range of 2-8 (optimum at pH 5), with adsorption capacities of 359.24, 473.27, and 556.33 mg/g at 298, 308, and 318 K, respectively. The adsorption equilibrium follows the Sips isotherm, and the kinetics fit the pseudo-secondary/Elovich model, indicating heterogeneous chemical adsorption. Gold removal efficiency reaches 99.39 % in mixed ion solutions and remains as high as 68.88 % in actual electroplating wastewater. The adsorbent retained an adsorption efficiency of 90.96 % after five thiourea regeneration cycles. XRD/XPS and DFT (DOS/PDOS, ELF, IGMH) analysis supported electrostatically assisted coordination of N/O sites as the primary capture pathway.