Direct, Environmentally Friendly Recovery of Copper from E-Waste Using Picolinic Acid and Its Upcycling to Cu2O for Sustainable Propargylation of Isatins

Abstract

The rapid increase in electronic waste generation and its associated environmental burden necessitate sustainable metal recovery strategies. In this work, we demonstrate an eco-friendly and efficient method for selectively recovering copper from waste printed circuit boards (WPCBs) using picolinic acid, a low-cost, commercially available, and environmentally benign chelating agent. Process parameters including picolinic acid concentration, pH, leaching time, and temperature were systematically optimized, achieving high copper recovery under mild conditions. The resulting copper-picolinate complex was subsequently reduced using hydrazine hydrate to obtain phase-pure Cu₂O nanoparticles. The synthesized Cu₂O acted as an effective heterogeneous material for the nucleophilic addition (propargylation) of allenylborolane to isatins, demonstrating the application of recovered copper. This study highlights a closed-loop approach wherein copper is recovered through a green leaching process and upcycled into a functional heterogeneous material for an important organic transformation, offering a sustainable pathway for e-waste valorization.