Aqueous biphasic systems comprising copolymers and cholinium-based salts or ionic liquids: Insights on the mechanisms responsible for their creation

Recycling of metals from LiFePO4 battery cathode material by using ionic liquid based-aqueous biphasic systems

Lithium-ion batteries are essential for electric vehicles and energy storage devices. With the increasing demand for their production and the concomitant surge in waste generation, the need for an efficient and environmentally friendly recycling process has become imperative. This work presents a new approach for recycling of metals from the LiFePO4 (LFP) cathode material. The cathode material was first leached by a HCl solution without an oxidizing agent. Subsequently, an ionic-liquid-based aqueous biphasic system (IL-based ABS) was used for the separation of lithium and iron from leachate solutions, followed by a precipitation process. The influence of the acid concentration, solid-to-liquid ratio and leaching time on the leaching yield was investigated. UV-vis absorption spectra revealed the presence of mixed-valent iron in the leachate, with 83 ± 1% Fe(ii) and 17 ± 1% Fe(iii). The ABS systems comprised tributyltetradecylphosphonium chloride [P44414]Cl and a salting-out agent (HCl or NaCl). The extraction percentage of iron reached 90% and less than 1% of lithium was extracted under the studied optimal conditions. Further enhancement of iron extraction, reaching 98%, was achieved via a two-stage cross-current extraction process. Iron was precipitated from the loaded IL phase with an efficiency of 97% as Fe(OH)2 and Fe(OH)3, using an aqueous ammonia solution. Lithium was precipitated as Li3PO4 with a lithium purity of 99.5% by adding K3PO4 solution. The ionic liquid used in the process was efficiently regenerated and used in four extraction cycles with no activity decline, with an extraction percentage of 90% of iron in each cycle.

Aqueous Two-Phase Systems Based on Ionic Liquids and Deep Eutectic Solvents as a Tool for the Recovery of Non-Protein Bioactive Compounds—A Review

Aqueous two-phase systems (ATPS) based on ionic liquids (IL) and deep eutectic solvents (DES) are ecofriendly choices and can be used to selectively separate compounds of interest, such as bioactive compounds. Bioactive compounds are nutrients and nonnutrients of animal, plant, and microbial origin that benefit the human body in addition to their classic nutritional properties. They can also be used for technical purposes in food and as active components in the chemical and pharmaceutical industries. Because they are usually present in complex matrices and low concentrations, it is necessary to separate them in order to increase their availability and stability, and ATPS is a highlighted technique for this purpose. This review demonstrates the application of ATPS based on IL and DES as a tool for recovering nonprotein bioactive compounds, considering critical factors, results and the most recent advances in this field. In addition, the review emphasizes the perspectives for expanding the use of nonconventional ATPS in purification systems, which consider the use of molecular modelling to predict experimental conditions, the investigation of diverse compounds in phase-forming systems, the establishment of optimal operational parameters, and the verification of bioactivities after the purification process.

Enantioselective liquid-liquid extraction of tryptophan enantiomers by a recyclable aqueous biphasic system based on stimuli-responsive polymers

The hydrophobic organic solvents/water biphasic system had been always used in the traditional enantioselective liquid-liquid extraction (ELLE). In recent years, aqueous biphasic systems (ABSs) are considered as a promising method used in the ELLE. In the present work, a recyclable ABS composed of a temperature-responsive polymer poly(MAH-β-CD-co-NIPAAm) (P_N-CD) and a pH-responsive polymer poly(AA-DMAEMA-BMA) (P_ADB) was employed in the enantioseparation of tryptophan enantiomers. The polymer P_N-CD acted as not only the phase-forming component but also the chiral selector, which can be recycled by changing the temperature. The polymer P_ADB can be used as the phase-forming component, which can also be recycled by adjusting the pH. The phase behaviors of this P_N-CD/P_ADB ABS had been studied. The influencing parameters were studied for this chiral separation process, including the polymer concentration, initial tryptophan concentration, extraction temperature, and system pH. The maximum separation factor (α) of 1.42 was obtained by one-step extraction under the optimal conditions. Meanwhile, the distribution coefficients of L-tryptophan (L-Trp) and D-tryptophan (D-Trp) were 2.79 and 1.96, respectively. This study develops a green and sustainable strategy for enantioseparation by using the ELLE.