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Extracção por solventes na recuperação de Platina e Paládio
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Orientador(es)
Resumo(s)
O trabalho desenvolvido no âmbito desta dissertação teve como objecto de estudo a etapa de extracção
por solventes (ES) de uma abordagem hidrometalúrgica, na qual dois novos extractantes foram testados
para a recuperação de Pd(II) de soluções cloretadas acídicas modelo e reais. As diamidas foram
sintetizadas com sucesso e a sua caracterização foi realizada através de diversas técnicas cromatográficas
e espectroscópicas:
1) Derivado de tiodiglicolamida N,N’-dimetil-N,N’-diciclohexiltiodipropanamida
(DMDCHTDPA);
2) Derivado de ditiodiglicolamida N,N’-dimetil-N,N’-diciclohexilditiodipropanamida (DiSulfide).
Os testes preliminares demonstraram que a DMDCHTDPA em tolueno possui uma capacidade
extractiva praticamente total ao longo da gama de [HCl] testadas, ao contrário do Di-Sulfide. De seguida,
estudaram-se diversos parâmetros experimentais, como: o tempo de contacto necessário para se atingir
o equilíbrio, a [extractante] na fase orgânica e o solvente usado na sua diluição. A aplicabilidade e
robustez da DMDCHTDPA em sistemas hidrometalúrgicos avaliou-se através do estudo da sua
capacidade de reutilização, que se revelou completa e estável ao longo dos ciclos de
extracção/reextracção realizados. As isotérmicas de equilíbrio traçadas demonstram que a
DMDCHTDPA exibe uma boa capacidade de carregamento em Pd(II).
O estudo da influência da acidez ([H+]) e da concentração de iões cloreto ([Cl−]) da fase aquosa, em
conjunto com as informações recolhidas nos estudos complementares prévios, apontam para a formação
mais provável de complexos organometálicos Pd(II):DMDCHTDPA de composição 1:2, do tipo [PdCl2
∙ L2
], através de uma reacção de troca de ligandos. Na presença de outros metais, a
DMDCHTDPA é eficiente, mas não totalmente selectiva, para a extracção de Pd(II), ainda que a sua
capacidade extractiva para as outras espécies seja diminuta. Este comportamento mantém-se em
condições reais.
O comportamento da DMDCHTDPA em tolueno não difere muito do relatado para tiodiglicolamidas
de estrutura similar, previamente trabalhadas por este grupo de investigação, pelo que a co-extracção de
Al(III) em condições reais continua a ser um problema.
The research conducted within the framework of this dissertation focused on the solvent extraction (SX) phase of a hydrometallurgical process, wherein two novel extractants were evaluated for the recovery of Pd(II) from both model and real acidic chloride solutions. The diamides were synthesized and their characterization was carried out using various chromatographic and spectroscopic techniques: 1) Thiodiglycolamide derivative N,N’-dimethyl-N,N’-dicyclohexylthiodipropanamide (DMDCHTDPA); 2) Dithiodiglycolamide derivative N,N’-dimethyl-N,N’-dicyclohexyldithiodipropanamide (DiSulfide). Preliminary tests indicated that only DMDCHTDPA in toluene has near-complete extractive capacity across the range of [HCl] tested. Several experimental parameters were investigated, including the contact time required to reach equilibrium, the [extractant] in the organic phase, and the solvent employed for its dilution. The applicability of DMDCHTDPA in hydrometallurgical systems was assessed by examining its reusability, which remained complete and stable throughout the extraction/reextraction cycles performed. Equilibrium isotherms obtained describe DMDCHTDPA as having a good Pd(II) loading capacity. The investigation into the influence of acidity ([H+]) and chloride ion concentration ([Cl−]) in the aqueous phase, combined with data from prior complementary studies, points out to the formation of 1:2 Pd(II):DMDCHTDPA organometallic species ([PdCl2 ∙ L2]), established via complexation reaction by ligand exchange. In the presence of other metals, DMDCHTDPA demonstrates efficiency, albeit not complete selectivity, for the extraction of Pd(II), while its extractive capacity for other species remains minimal. This behavior persists when using real leach solutions. As previously documented for similarly structured thiodiglycolamide derivatives, DMDCHTDPA in toluene exhibits some affinity to Al(III) under real conditions, which inhibits the Pd(II) interaction with the stripping agents, decreasing the overall efficiency of the process.
The research conducted within the framework of this dissertation focused on the solvent extraction (SX) phase of a hydrometallurgical process, wherein two novel extractants were evaluated for the recovery of Pd(II) from both model and real acidic chloride solutions. The diamides were synthesized and their characterization was carried out using various chromatographic and spectroscopic techniques: 1) Thiodiglycolamide derivative N,N’-dimethyl-N,N’-dicyclohexylthiodipropanamide (DMDCHTDPA); 2) Dithiodiglycolamide derivative N,N’-dimethyl-N,N’-dicyclohexyldithiodipropanamide (DiSulfide). Preliminary tests indicated that only DMDCHTDPA in toluene has near-complete extractive capacity across the range of [HCl] tested. Several experimental parameters were investigated, including the contact time required to reach equilibrium, the [extractant] in the organic phase, and the solvent employed for its dilution. The applicability of DMDCHTDPA in hydrometallurgical systems was assessed by examining its reusability, which remained complete and stable throughout the extraction/reextraction cycles performed. Equilibrium isotherms obtained describe DMDCHTDPA as having a good Pd(II) loading capacity. The investigation into the influence of acidity ([H+]) and chloride ion concentration ([Cl−]) in the aqueous phase, combined with data from prior complementary studies, points out to the formation of 1:2 Pd(II):DMDCHTDPA organometallic species ([PdCl2 ∙ L2]), established via complexation reaction by ligand exchange. In the presence of other metals, DMDCHTDPA demonstrates efficiency, albeit not complete selectivity, for the extraction of Pd(II), while its extractive capacity for other species remains minimal. This behavior persists when using real leach solutions. As previously documented for similarly structured thiodiglycolamide derivatives, DMDCHTDPA in toluene exhibits some affinity to Al(III) under real conditions, which inhibits the Pd(II) interaction with the stripping agents, decreasing the overall efficiency of the process.
Descrição
Tese de Mestrado, Química, 2024, Universidade de Lisboa, Faculdade de Ciências
Palavras-chave
PGMs Pd(II) Tiodiglicolamidas Extracção líquido-líquido Catalisadores Teses de mestrado - 2024