Efficient and selective gold recovery using a green iodine-iodide leaching system assisted by a synergistic ZnO-GO nanocomposite photocatalyst

The sustainable recovery of precious metals from electronic waste using environmentally benign processes has emerged as an important research focus in modern separation technologies. In the present work, ZnO, graphene oxide (GO), and a ZnO-GO nanocomposite were synthesized and comparatively investigated for photocatalytic gold dissolution in a green iodine-iodide leaching system under light irradiation. Structural and morphological analyses confirmed the successful formation of the ZnO-GO heterostructure with improved interfacial contact between ZnO nanoparticles and GO sheets. Photocatalytic experiments revealed pristine ZnO achieved 86.33% gold dissolution within 120 min, whereas GO exhibited enhanced dissolution efficiency of 95.1% under identical conditions. Remarkably, the ZnO-GO nanocomposite demonstrated outstanding photocatalytic activity, attaining 99.93% gold dissolution within 120 min with excellent reproducibility. The significantly enhanced performance of the heterostructure attributed to the synergistic interaction between ZnO and GO, which promotes efficient charge separation and suppresses electron-hole recombination. GO acts as an electron acceptor and conductive transport pathway, thereby accelerating iodide oxidation and facilitating the rapid formation of soluble gold-iodide complexes. Kinetic analysis further confirmed the superior reaction rate of the ZnO-GO system compared with individual components. The developed photocatalytic approach offers a highly efficient, selective and environmentally sustainable strategy for gold recovery from electronic waste, demonstrating strong potential for advanced separation and resource recovery applications.