Centre of Marine Sciences

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Leaching efficiency and kinetics of the recovery of palladium and rhodium from a spent auto-catalyst in HCl/CuCl2 media

Publication . Nogueira, Carlos; Paiva, A. P.; Costa, M. Clara; Costa, Ana M. Rosa da

ABSTRACT: The recycling of scarce elements such as platinum-group metals is becoming crucial due to their growing importance in current and emerging applications. In this sense, the recovery of palladium and rhodium from a spent auto-catalyst by leaching in HCl/CuCl2 media was studied, aiming at assessing the kinetic performance as well as the influence of some processing factors, and the behaviour of contaminant metals. Based on a kinetic model developed for the present case, the influence of temperature was evaluated and the corresponding values of activation energy were estimated as 60.1 ± 4.1 kJ mol−1 for Pd and 44.3 ± 7.3 kJ mol−1 for Rh, indicating the relevance of the chemical step rather than diffusion. This finding was corroborated by the nonsignificant influence of the stirring velocity. The reaction orders were estimated for each leaching reagent: for HCl, values of 2.1 ± 0.1 for Pd and 1.0 ± 0.3 for Rh were obtained; for Cu2+, the obtained values were 0.42 ± 0.04 for Pd and 0.36 ± 0.06 for Rh. Without any significant loss of efficiency, solutions with higher metal concentrations were obtained using lower liquid/solid ratios, such as 5 L/kg. The main contaminant in solution was aluminum, and its leaching was found to be very dependent on the temperature and acid concentration.

2019Journal article

Open access

Ionic liquids in the solvent extraction of platinum-group metals : how far can they go?

Publication . Paiva, A. P.; Costa, M. Clara; Nogueira, Carlos

ABSTRACT: Ionic liquids (ILs) are molten salts that are liquid at room temperature. Although their existence has been known from the beginning of the 20th century, only at the end of the 80's - beginning of 90´s their characteristic properties and potential advantages began to be widely explored. Nowadays there is no doubt that ILs have become a major subject of research for modern chemistry, and the industry progressively starts to include ILs in chemical processes. This communication presents and discusses some relevant results found in literature concerning the application of ILs to recover platinum-group metals (PGMs) from complex leaching solutions by solvent extraction (SX). Based on the available data, an evaluation about the forthcoming of ILs to recover PGMs from real leaching solutions of spent catalysts will be assessed.

2019Conference object

Open access