Three-Dimensional, Vertical Platelets of ZnO Carriers for Selective Extraction of Cobalt Ions from Waste Printed Circuit Boards

Controlled design of low-cost, ecofriendly, and efficient metal recycling process of waste printed circuit boards (PCBs) is essential for sustainable industries. In this study, a metal extractor (ME) design was fabricated by anchoring organic chromophore chelate [(E)-4-((3-amino-4-hydroxyphenyl)diazenyl)naphthalen-1-ol (AHPDN)] into three-dimensional (3D) and vertical platelets of ZnO platforms to continuously extract and sensitively and selectively detect ultratrace Co2+ concentration (∼95.7%) in real e-waste leach liquor. Results reveal that the microscopic ZnO platelet hierarchy is successfully fabricated with nonstacked 3D platelet morphology through hydrothermal-assisted methodology. The 3D nonstacked ZnO platelets are oriented in horizontal and vertical domains, thereby enabling fabrication of potential ME for multidirectional diffusion and efficient adsorptivity of Co2+ ions. Multidiffusible, intermingled platelets and numerous active sites that decorated the ME hierarchy promote the ultratrace sep...