Green Recovery of Precious Metals from Discarded Waste through a Peroxymonosulfate-Based Homogeneous Fenton-Like System

Abstract

Precious metal (PM) recovery from discarded waste is essential to mitigate supply risks; however, traditional methods typically cause substantial environmental harm. This study presents a novel leaching process employing a low-concentration peroxymonosulfate (PMS)/CoCl₂ Fenton-like system for the efficient recovery of gold (Au), palladium (Pd), and platinum (Pt) from electronic waste and spent catalysts. Through electron paramagnetic resonance spectroscopy, ¹⁸O isotope tracing, and density functional theory calculations, SO₄·^–, ·OH, and reactive Co species were identified as the primary reactive species responsible for the oxidative dissolution of the PMs. Notably, the spontaneous cycling between Co(II) and Co(III) oxidation states sustained the solution’s reactivity for over 12 consecutive cycles. To demonstrate the efficacy of this method, hectogram quantities of spent Pd/C catalyst were processed, yielding 1.97 g of high-purity Pd. Operating at room temperature and without the need for strong acids or toxic cyanides, this method offers a sustainable alternative for PM recovery. Furthermore, this study highlights the broader potential of advanced oxidation processes for the efficient and environmentally friendly recycling of secondary resources.