New challenges and applications of supported liquid membrane systems based on facilitated transport in liquid phase separations of metallic species

The linear economic model based on "take-make-dispose" has become unsustainable, revealing the necessity of shifting towards a circular economy (CE) approach, in which secondary raw materials play a key role in closing material cycles. In this context, industrial effluents with metallic content, are considered a potential secondary source for these elements, the lack of the availability of the appropriate technology being the main barrier when implementing circular economy principles at industrial scale. In this regard, supported liquid membrane (SLM) systems based on facilitated transport may be decisive. Thus, the objective of this research paper is to show the potential of facilitated transport systems to foster the transition to a more sustainable management of industrial metallic effluents. To accomplish that, three different applications of supported liquid membrane systems in acidic industrial effluents will be presented: a) Zn/Fe separation, b) Ni/Cd separations and c) Removal of hexavalent Cr. Additionally, the recovery and separation of two different critical raw materials, i.e. Li and rare earth elements will be discussed. Although facilitated transport systems have been successfully applied to both, Zn/Fe and Ni/Cd separation, as well as to hexavalent Cr removal, further work should be done for the successful recovery and separation of Li and rare earths with supported liquid membrane systems, especially in terms of selectivity improvement and validation with real industrial effluents.Financial support from the Spanish Ministry of Science, Innovation and Universities under the projects PID2020-115409RB-I00 and RTI2018-093310-B-I00 are gratefully acknowledged

Selective extraction of lithium from seawater desalination concentrates: study of thermodynamic and equilibrium properties using Density Functional Theory (DFT)

Lithium, declared critical raw material by the European Union in 2020, is a competitor to hydrogen as alternative to petroleum. Its use is increasing while reserves are declining, boosting new sources, as seawater desalination concentrates. In this work, a computational study of the most promising extractants, B-diketones and organophosphates and combinations thereof, towards lithium in presence of metal ions found in the concentrates, Na+, K+, Mg2+, Ca2+ and Sr2+ was carried out, via molecular simulation using ab initio Density Functional Theory (DFT). The geometries, reaction energies, and thermodynamic parameters have been evaluated. Using the square of the electronic wave function an electrostatic interaction was confirmed as cation-extractant/s bonding. The complexation reaction energies of the systems formed by a cation and a single extractant display negative [delta]E and [delta]G values, pointing towards stable complexes and spontaneous reactions. The synergic effect of extractants was studied by combining the [beta]-diketones with TOPO (1:1) leading to an increase of [delta]E and [delta]G (absolute value). The extraction coefficient, K, follows the order K(K+) > K(Na+) > K(Li+) > K(Sr2+) > K(Ca2+) > K(Mg2+). In consequence, selectivity Li+ towards cations of the group II was higher, S(Li+/Mg2+) > S(Li+/Ca2+) > S(Li+/Sr2+) for the combined mixtures BTA TOPO and FDOD TOPO and lower towards group I cations, S(Li+/Na+) > S(Li+/K+) for DBM TOPO and LIX54 TOPO. The selectivity of Li+ regarding the rest of the cations and the 16 extractants and mixtures of extractants was lower than the selectivity of Li+ with respect to each cation, being the best value for the DBM TOPO and LIX54 TOPO systems. The results obtained are expected to provide a tool on the behaviour of the most promising of extractants towards Li+ in seawater desalination concentrates.This research was developed in the framework of the project PID2020-115409RB-I00 financed by the Ministry of Science and Innovation (Spain)

Preliminary study of Li⁺ recovery from desalination plant concentrates using β-diketones and organophosphorus

RESUMEN: Debido al rápido desarrollo de la tecnología de los dispositivos móviles y del sector automovilístico, el consumo de litio tiende a incrementar cada vez más. Actualmente, este elemento se obtiene principalmente mediante la tecnología evaporítica, en la que se concentran lagos salados mediante evaporación solar y eólica. Entre las desventajas de este proceso se encuentra el tiempo (1 - 2 años), su dependencia de las condiciones climáticas, el gran consumo de agua y generación de residuos. En este sentido, este Trabajo Fin de Máster pretende contribuir, con un estudio preliminar, a la recuperación de Li⁺ a partir de fuentes secundarias de materias primas, como son los concentrados de desaladoras, en el marco de la Economía Circular. Para ello, se seleccionó la tecnología de extracción líquido-líquido debido a su bajo costo, fácil operatividad, bajo consumo de productos químicos, eficacia de extracción, extractantes reciclables y facilidad de escalar a nivel industrial. El estudio del estado del arte muestra como la mayoría de las recuperaciones de Li⁺ descritas en la literatura se han realizado principalmente con los metales alcalinos encontrados en las salmueras, excluyendo muchos de estos trabajos a los cationes alcalinotérreos, especialmente al Sr²⁺. A partir del estudio de la bibliografía, se puede concluir que las mezclas β-dicetona-ligando solvatante son las más selectivas a la extracción del Li⁺ en medios alcalinos. A partir de las conclusiones alcanzadas en la bibliografía, se llevó a cabo un estudio de las propiedades termodinámicas (energía de reacción (ΔE) y energía libre de Gibbs (ΔG)), mediante simulación molecular, de la extracción de Li⁺ con las β-dicetonas DBM, LIX 54, TTA, FTA, BTA y FDOD, y los ligandos organofosforados TOPO, TBP, TRIS y BIS, previamente seleccionados de la literatura, en colaboración con el Departamento de Ciencias de la Tierra y Física de la Materia Condensada de la Universidad de Cantabria. De este estudio resultó que la combinación de extractantes simulados con mayor energía de reacción y mayor energía de Gibbs fue la mezcla dibenzoilmetano (DBM) + óxido de trioctilfosfina (TOPO) (ΔE=-86 kcal/mol, ΔG=-64 kcal/mol), indicando ser la mezcla más eficaz para la extracción de Li⁺. A partir del desarrollo experimental de la isoterma de extracción, se obtuvo que el 95,44 ± 0,61% de este catión se extrae en medio alcalino entre pH 9,0 y pH 12,25. Un análisis de la influencia del tiempo conllevó a que en tan solo 5 min se alcanza el equilibrio. Este comportamiento se encuentra relacionado con el efecto tautomérico de la β-dicetona. El Diseño Central Compuesto permitió ajustar los resultados experimentales a un modelo matemático (R2=96,21% y R2 ajustado=93,99%) que describe la influencia de las variables independientes (proporción de extractante respecto al litio ([Ext]:[Li]), concentración de NH3 ([NH3]), y fracción molar de DBM (x(DBM))) en la variable respuesta (% Extracción). Como ejecución óptima el modelo predice la combinación de valores de los factores [Ext]:[Li]=232,33, [NH3]=1,60 M y x(DBM)=0,46, con un valor de extracción del 99,7% con un intervalo de confianza de 96,1% - 103,3%. Para su comprobación se realizó el experimento obteniéndose un 96,97 ± 0,00%, el cual entra dentro del intervalo de confianza predicho. Finalmente, se comprobó como agente re-extractante al HCl, alcanzándose con una concentración de HCl 2,0·10⁻⁴ M (menor que la estequiométrica), una extracción de un 78,42 ± 0,74% de Li⁺, y con apenas HCl 1,0·10⁻³ M es suficiente para recuperar el 100 ± 0,00% de Li⁺ de la fase orgánica (1,7 veces estequiométricamente).ABSTRACT: Due to the rapid development of mobile device technology and the automobile sector, the consumption of lithium is tending to increase more and more. At present, lithium is mainly obtained by evaporitic technology, in which salt lakes are concentrated by solar and wind evaporation. Among the disadvantages of this process are the time (1 - 2 years), its dependence on climatic conditions, high water consumption and waste generation. In this sense, this Master's Thesis pretends to contribute, with a preliminary study, to the recovery of Li⁺ from secondary sources of raw materials, such as desalination plant concentrates, within the framework of the Circular Economy. For this purpose, liquid-liquid extraction technology was selected due to its low cost, easy operation, low chemical consumption, extraction efficiency, recyclable extractants and ease of industrial scale-up. The study of the state of the art shows that most of the Li⁺ recoveries described in the literature have been carried out mainly with the alkali metals found in brines, with many of these works excluding the alkaline earth cations, especially Sr²⁺. From the literature review, it can be concluded that β-diketone-solvent ligand mixtures are the most selective for Li⁺ extraction in alkaline solutions. The study of the state of the art shows that most of the Li⁺ recoveries described in the literature have been carried out mainly with the alkali metals found in brines, with many of these works excluding the alkaline earth cations, especially Sr²⁺. From the literature review, it can be concluded that β-diketone-solvent ligand mixtures are the most selective for Li⁺ extraction in alkaline solutions. Based on the conclusions reached in the literature, a study of the thermodynamic properties (reaction energy (ΔE) and Gibbs free energy (ΔG)) of Li⁺ extraction with the β-diketones DBM, LIX 54, TTA, FTA, BTA and FDOD, and the organophosphorus ligands TOPO, TBP, TRIS and BIS, previously selected from the literature, was carried out by molecular simulation in collaboration with the Department of Earth Sciences and Condensed Matter Physics of the University of Cantabria. From this study it was found that the combination of simulated extractants with the highest reaction energy and Gibbs energy was the mixture dibenzoylmethane (DBM) + trioctylphosphine oxide (TOPO) (ΔE=-86 kcal/mol, ΔG=-64 kcal/mol), indicating to be the most efficient mixture for the extraction of Li⁺. From the experimental development of the extraction isotherm, it was obtained that 95.44 ± 0.61% of this cation is extracted in an alkaline medium between pH 9.0 and pH 12.25. An analysis of the influence of time showed that equilibrium was reached in only 5 min. This behaviour is related to the tautomeric effect of β-diketone. The Central Composite Design allowed fitting the experimental results to a mathematical model (R2=96.21% and adjusted R2=93.99%) that describes the influence of the independent variables (ratio of extractant to lithium ([Ext]: [Li]), NH3 concentration ([NH3]), and mole fraction of DBM (x(DBM)) on the response variable (% Extraction). As optimal run the model predicts the combination of values of the factors [Ext]: [Li]=232.33, [NH3]=1.60 M and x(DBM)=0.46, with an extraction value of 99.7% with a confidence interval of 96.1% - 103.3%. For its verification, the experiment was carried out obtaining 96.97 ± 0.00%, which is within the predicted confidence interval. Finally, HCl was tested as a re-extracting agent, reaching an extraction of 78.42 ± 0.74% of Li+ with a concentration of 2.0·10⁻⁴ M HCl (lower than stoichiometric), and with only 1.0·10⁻³ M HCl it is enough to recover 100 ± 0.00% of Li+ from the organic phase (1.7 times stoichiometrically).Máster en Ingeniería Químic

Simulation of a bioetanol manufacturing process using a residue of Ulva rigida as feedstock

Grado en Ingeniería Químic