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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.
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.
A two-stage cultivation strategy for the industrial production of the novel microalga Chlorococcum amblystomatis
Publication . Correia, Nádia; Trovão, Mafalda; Santo, Gonçalo E.; Guerra, Inês; Cunha, P.; Fonseca, Joana; Pereira, Hugo; Costa, Monya M.; Ferreira, Sara; Santos, Tamára; Barros, Ana; Cardoso, Helena; Silva, Joana; Gouveia, Luisa; Varela, João
ABSTRACT: This study presented the industrial-scale validation of a two-stage growth strategy for a poorly explored yet industrially relevant chlorophyte microalga, Chlorococcum amblystomatis, addressing the gap between laboratory research and practical application. By using cultures grown heterotrophically as inoculum for industrial-scale photoautotrophic reactors, this approach significantly accelerated scale-up. The proposed strategy reduced the overall scale-up time by approximately 5.5-fold compared to the conventional pipeline, without compromising productivity or biochemical quality. A maximum biomass concentration of 70.96 +/- 0.35 g L-1 was achieved in 7-L benchtop fermenters under heterotrophic conditions, representing the highest value reported to date for this microalga. The biomass obtained presented a protein content of 32.42 +/- 2.30% of dry weight, which increased to 54.55 +/- 2.04% upon cultivation under photoautotrophic conditions, as well as polyunsaturated fatty acids, which increased from 50.12 +/- 3.27 to 67.74 +/- 0.35% of total fatty acids, with alpha-linolenic acid as the predominant fatty acid. Conversely, the saturated fatty acids content (38.26 +/- 1.63% of TFA) decreased to 22.37 +/- 0.02% of TFA in the phototrophic stage. Pigment contents also increased significantly during the phototrophic stage, with chlorophylls rising from 10.04 +/- 1.68 to 44.91 +/- 5.11 mg g(-)1 and carotenoids reaching notable concentrations, including lutein (5.34 +/- 0.10 mg g-1), beta-carotene (5.92 +/- 0.39 mg g-1), and neoxanthin (3.53 +/- 0.75 mg g-1). Among the industrial photoautotrophic systems tested, the closed tubular photobioreactors were the most suitable configuration for C. amblystomatis cultivation, achieving higher biomass productivity, enhanced protein content and pigment accumulation compared to open raceway ponds. Overall, this work demonstrates a scalable, efficient, and time-saving cultivation strategy for C. amblystomatis, supporting its potential for industrial biotechnological applications.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
6817 - DCRRNI ID
Número da atribuição
UID/Multi/04326/2019