Abstract
By the use of the tertiary amine A327 and 1 M HCl solution as precursors, the ionic liquid A327H+Cl− was generated and used to investigate its performance in the transport of Au(III) from hydrochloric acid medium. The influence of the stirring speed (600–1800 min−1), ionic liquid concentration (1.25–50% v/v) in the membrane phase, and gold concentration (0.01–0.15 g/L) in the feed phase on metal transport have been investigated. An equation which included both equilibrium and kinetics parameters was derived, and the membrane diffusional resistance (Δm) and feed phase diffusional resistance (Δf) was estimated as 9.5 × 106 s/cm and 307 s/cm, respectively. At carrier concentrations in the 5–50% v/v range and gold concentrations in the 0.01–0.15 g/L range, metal transport is controlled by diffusion of metal species through the feed boundary layer, whereas at the lowest carrier concentrations, membrane diffusion is predominant. From the receiving solutions, gold can be recovered as gold nanoparticles.
Highlights
Nowadays the presence of metals in urban environments is a norm, such as the necessity of recycling of the materials contained in them, and the concept of urban mining arises
Liquid membranes processes have been of increasing interest against liquid-liquid extraction, or even ion exchange and adsorption processes, for the separation and concentration of metals, from dilute aqueous solutions, due to the fact that they combine in a single operation the extraction and stripping stages
The precursors for the generation of the ionic liquid were the tertiary amine A327 (Sanofi), which is composed by a 50% mixture of tri-octyl and tri-decyl amines, with average molecular weight of 395 and density 0.82 g/cm3 (20 ◦ C), the reagent was diluted in toluene (Fluka, Madrid, Spain) in order to adequately determine the range of amine concentrations, and of the ionic liquid to the gold transport experiments
Summary
Nowadays the presence of metals in urban environments is a norm, such as the necessity of recycling of the materials contained in them, and the concept of urban mining arises. In the treatment of these e-wastes, hydrometallurgy can be an option; this technology included leaching of the product yielded from the corresponding pre-treatment of the solid waste (dismantling, shedding, comminution), and separation and recovery of the valuable elements from the leachate Among these separation technologies, liquid membranes processes have been of increasing interest (though not a single process has been yet installed in industrial form) against liquid-liquid extraction, or even ion exchange and adsorption processes, for the separation and concentration of metals, from dilute aqueous solutions, due to the fact that they combine in a single operation the extraction and stripping stages. The treatment of the receiving solutions with sodium borohydride leads to the precipitation of gold as nanoparticles
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