Highly efficient gold recovery from electronic waste through employing 3D printed Polyethylenimine/graphene oxide/calcium alginate multilevel Macroporous adsorbent

Abstract

With the rapid development of the electronics industry, efficient gold recovery from electronic waste bears substantial economic benefits and carries profound ecological importance. In this study, by means of 3D printed technology, a polyethylenimine/graphene oxide/calcium alginate (3D PGCs) composite adsorbent with millimeter-to-micrometer multilevel macroporous morphology has been successfully constructed. Excellent hydrophilicity and gold adsorption capacity have been confirmed, with values of 1057 mg g−1 (at 298.15 K), 1395 mg g−1 (at 308.15 K), and 1527 mg g−1 (at 318.15 K) being achieved for Au(III) adsorption under a pH of 2.5, respectively. This remarkable adsorption performance is attributed to its multi-scale structural optimization and abundant surface-active functional groups (nitrogen and oxygen-containing groups). Characterization suggests that the adsorption of Au(III) on the 3D PGCs surface is attributed to the synergistic effects of electrostatic interactions and redox reactions. Furthermore, 3D PGCs displays a highly efficient selective adsorption capability for Au(III), maintaining a high adsorption capacity even after 8 cycles of repeated adsorption–desorption. In practical applications, without pH adjustment, the specific selectivity of 3D PGCs for Au(III) in real acidic gold-containing aqueous solution reaches up to 96 %. Furthermore, the gold adsorbed on the 3D PGCs can be desorbed through acid washing, and subsequently reduced using oxalic acid to obtain foam gold. After calcination, elemental gold can be obtained, thereby achieving gold recovery. Therefore, owing to its exceptional multi-level macroporous structure and modified active functional groups, 3D PGCs presents efficient selective adsorption capability for Au(III) in acidic aqueous solutions, indicating substantial potential to be applied in the efficient gold recovery from electronic waste.