Recovery and Then Individual Separation of Platinum, Palladium, and Rhodium from Spent Car Catalytic Converters Using Hydrometallurgical Technique followed by Successive Precipitation Methods

Ahmed M Yousif

doi:10.1155/2019/2318157

Abstract

Recovery of PGMs (especially rhodium, platinum, and palladium) from different spent manufactured products (like catalytic converters) is considered as an important task as they are rarely found in nature, and they possess high economic value. In this work, the honeycomb of a car catalytic converter was primarily processed by crushing, grinding, and then treating in a hydrogen atmosphere. In order to establish an economic and ecofriendly method for the recovery of studied PGMs, different experimental conditions of changing HCl/H2O2 (as a leaching solution) ratio, temperature, and contact time were studied through batch experiments to obtain the optimum leaching conditions. The use of 0.8 vol% H2O2 and 9.0 M HCl mixture at 60°C for a contact time of 2.5 hours during the leaching process may be considered as the best conditions to be followed to save chemicals, energy, and time (about 86%, 96%, and 98% of Rh, Pt, and Pd were recovered, respectively). Individual separation of PGM ions from each other using precipitation technique from their leaching liquor was performed where % purity values of 99.5, 99.3, and 95.5 were obtained for Pt, Pd, and Rh, respectively.

Highlights

In order to reduce the nitrogen oxide, hydrocarbon, and carbon monoxide emissions produced by different vehicle engines, it has been a must for all vehicles produced since 1993 to be fitted with catalytic converters
Different experimental conditions of changing HCl/H2O2 ratio, temperature, and contact time were studied for the leaching processes to obtain the optimum leaching conditions
Gas bubbles were observed after the addition of H2O2 to the leaching solutions which were considered as a primary evidence of the formation of chlorine gas active species as illustrated in the following equation: H2O2(aq) + 2HCl(aq) ⟷ Cl2(g) + 2H2O

Summary

Introduction

In order to reduce the nitrogen oxide, hydrocarbon, and carbon monoxide emissions (they are considered as harmful gases) produced by different vehicle engines, it has been a must for all vehicles produced since 1993 to be fitted with catalytic converters. PGMs from spent catalytic converters using different metallurgical and refining methods through the use of smelting furnaces, hydrogen pretreatment, and/or direct leaching of PGMs [4, 7,8,9]. Erefore, these facts lead us to think about the use of efficient and ecofriendly leaching processes. Efforts were directed to recover PGMs from processed spent catalytic converters (after pretreatment in a hydrogen atmosphere) using harmless leaching mixtures of hydrochloric acid and hydrogen peroxide as an oxidant (without any harmful gas emission or a residual byproduct generation during the process). Other experiments were conducted to individually separate PGMs from each other in the leaching liquor using the precipitation technique

Experimental

Results and Discussion

Conclusions