Recovery of Platinum Group Metals from Spent Automotive Catalysts Using Lithium Salts and Hydrochloric Acid

Abstract

The recovery of platinum group metals (PGMs) from waste materials involves dissolving the waste in an aqueous solution. However, since PGMs are precious metals, their dissolution requires strong oxidizing agents such as chlorine gas and aqua regia. In this study, we aimed to recover PGMs via the calcination of spent automotive catalysts (autocatalysts) with Li salts based on the concept of “spent autocatalyst + waste lithium-ion batteries” and leaching with only HCl. The results suggest that, when Li2CO3 was used, the Pt content was fully leached, while 94.9% and 97.5% of Rh and Pd, respectively, were leached using HCl addition. Even when LiF, which is a decomposition product of the electrolytic solution (LiPF6), was used as the Li salt model, the PGM leaching rate did not significantly change. In addition, we studied the immobilization of fluorine on cordierite (2MgO·2Al2O3·5SiO2), which is a matrix component of autocatalysts. Through the calcination of LiF in the presence of cordierite, we found that cordierite thermally decomposed, and fluorine was immobilized as MgF2.

Extraction of platinum group metals from catalytic converters

“…Various techniques are applied to extract PGMs from catalytic converters [ 114 , [125] , [126] , [127] , [128] ], including pyrometallurgical and hydrometallurgical methods with subsequent element recovery [ 55 , 106 , 110 , [129] , [130] , [131] , [132] , [133] , [134] , [135] , [136] , [137] , [138] ], biological methods [ 139 , 140 ], leaching methods [ 109 , [141] , [142] , [143] , [144] , [145] , [146] ], solvometallurgical methods [ [147] , [148] , [149] , [150] , [151] ], molecular recognition technology [ [152] , [153] , [154] , [155] , [156] , [157] ] and biometallurgical methods [ [158] , [159] , [160] , [161] , [162] , [163] , [164] , [165] , [166] ]. These methods collectively ensure effective and eco-friendly processing of PGMs.…”

In Situ Mechanochemical Treatment of the Fe–Si–PGMs Alloy for Enhanced Platinum Group Metal Recovery: Overcoming Thermodynamic and Kinetic Barriers

“…One approach is to use alkaline roasting to convert the PGMs into their corresponding salts (such as Na 2 PtO 3 and Li 2 PtO 3 ), which can subsequently be leached with common inorganic acids to achieve PGM extraction. However, the complete oxidation of PGMs to salts and the feasibility of the process still require further investigation. − Another approach is to treat the matrix elements, Fe and Si, in the alloy so that their phases are transformed into their corresponding salts and removed while the PGMs are enriched. Dong et al used NaOH to roast Fe–Si–PGMs alloy, followed by water leaching and sulfuric acid leaching to remove NaFeO 2 , Fe 2 O 3 , and Na 4 SiO 4 formed by Fe and Si and the PGMs were enriched nine times at a content of 23.4% present in residue .…”

Plasma Regeneration of Spent Pd/Al2O3 Catalysts and Their Electrochemical Performance

“…Conventional approaches for recovering precious metals from waste catalysts mainly involve mechanical disassembly, chemical leaching, inciner-ation, or even microwave radiation. For example, Kuzuhara et al 14 extracted platinum group metals (PGMs) from spent automotive catalysts using calcination combined with acid leaching. Fang et al 15 reported the recovery of Pt and Rh from waste catalysts using a boiling solution containing HCl and HNO 3 .…”