Toward Eco‐Friendly E‐Waste Recycling: New Perspectives on Ozone‐Assisted Gold Leaching

Abstract

Global demand for more effective methods to reclaim gold from electronic waste (E‐waste) has never been greater. Alternatives to hydrometallurgical methods, such as cyanide, are still limited. This work examines utilizing ozone and chlorides to recycle Au from E‐waste. It is started with a fundamental investigation of Au dissolution processes on the extended surface of Au polycrystalline and Au nanoparticulated electrodes. An online electrochemical scanning flow cell coupled with inductively coupled plasma mass spectrometry quantifies the rates and amounts of Au leaching. Identical‐location scanning electron microscopy (IL‐SEM) further correlates dissolution events with electrode morphological changes. It is demonstrated that ozone in the electrolyte imposes an anodic potential on the electrode, leading to anodic Au dissolution. Passivation disappears when small amounts of chlorides are added to the electrolyte, significantly enhancing the leaching yield. IL‐SEM images of gold nanoparticles (NPs) before and after exposure to ozone reveal heterogeneity in NP size‐dependent dissolution, showing higher dissolution for smaller particles. An effective Au leaching procedure is further demonstrated in a lab‐scale reactor using real E‐waste where almost complete recovery of Au is achieved. This research suggests that with engineering optimization in reactor applications based on ozone‐stimulated gold, dissolution can pave the way for environmentally friendly gold recycling.