Abstract
In this research, a recycling process for palladium using “dry aqua regia,” which consists of iron(III) chloride–potassium chloride, was proposed. Palladium was dissolved in “dry aqua regia,” and the dissolved palladium was recovered by leaching with potassium chloride solution with added ammonium chloride and nitric acid. Palladium was almost completely dissolved in 3 h at 600 K, and the recovery ratio of dissolved palladium was up to 80%. In addition, the dissolution of palladium in coexistence with platinum and the dissolution of platinum-palladium alloy by “dry aqua regia” were also tested. The dissolved palladium and platinum were separated and recovered by solid–liquid separation technique using the difference in solubility of their compounds in potassium chloride and sodium chloride solutions. As a result, pure compounds of each element were recovered. This result suggested the possibility of using “dry aqua regia” for the separation of platinum-group metals.Graphical
Highlights
Platinum (Pt) and palladium (Pd) are platinum-group metals (PGMs), which are important metals for jewelry, coins, and other industrial applications, owing to their high catalytic abilities and chemical stability
It is suggested that Pd can be more dissolved than Pt by treatment with dry aqua regia
The authors confirmed the dissolution of Pd using dry aqua regia and its recovery by the precipitation process
Summary
Platinum (Pt) and palladium (Pd) are platinum-group metals (PGMs), which are important metals for jewelry, coins, and other industrial applications, owing to their high catalytic abilities and chemical stability. They are often used as automotive catalysts, approximately 40% of Pt and 75% of Pd and rhodium (Rh) were consumed [1, 2]. Panda et al summarized these efforts in the previous review [3] Both pyrometallurgical and hydrometallurgical recycling impose large environmental loads due to the energy consumption and the generation of waste liquids, use of chlorine (Cl2), etc. It lacks userfriendliness because of additional treatments required, such as electrolysis or Cl2 gas blowing
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