Green Leaching of Metallic Platinum Using an Ionic Liquid with Synergistic Organic Acid–Chlorinating Agent Additives

Abstract

This study explored the potential for an environmentally friendly method for refining difficult-to-solubilise noble metals (notably platinum). Conventional noble-metal refining processes rely on the use of strong inorganic acids and oxidants, which cause significant environmental impact. To overcome these challenges, we propose a non-aqueous direct leaching process using an ionic liquid, an organic acid, and a chlorinating agent. Our findings indicate that trihexyl(tetradecyl)phosphonium chloride (P66614Cl) in combination with methanesulfonic acid and trichloroisocyanuric acid effectively solubilises metallic platinum. We investigated the leaching mechanism using ultraviolet–visible spectroscopy and confirmed that Pt(0) was oxidised to Pt(IV) to form PtCl62−. Recovery of Pt from Pt-loaded P66614Cl was achieved by stripping with ammonium nitrate solution. This work advances the development of sustainable refining methods for noble metals.

Keywords

• Ionic liquid
• Non-aqueous leaching
• Platinum
• Oxidative dissolution
• Sustainable metallurgy