A Fundamental Study of Platinum Recovery from Spent Auto-Catalyst Using “Dry Aqua Regia”

Abstract

In this paper, a novel method for recovering platinum using molten FeCl₃-KCl system as “dry aqua regia” is presented. The method consists of the dissolution of platinum by molten FeCl₃-KCl system and the recovery of dissolved platinum by the solvent leaching of frozen FeCl₃-KCl, using the different solubility between platinum compounds and iron compounds for the solvents. Platinum dissolution was conducted in the molten FeCl₃-KCl system at 585-655 K. The maximum dissolution rate of platinum was 0.45 mol･m⁻²･h⁻¹, which is fast enough compared with the hydrometallurgy process using aqua regia or electrochemical dissolution process in ionic liquid. And dissolved platinum recovered as K₂(PtCl₆) by the solvent leaching of frozen FeCl₃-KCl using water or ethanol. This “dry aqua regia” process have a number of advantages, including low energy consumption, easy operation and low toxicity of chemicals compared with pyrometallurgy process and hydrometallurgy process, as recycling process of platinum.