Modelling and Comparative Analysis of Different Methods of Liquid Membrane Separations

Abstract

This article is devoted to a brief review of the modelling of liquid membrane separation methods, such as emulsion, supported liquid membranes, film pertraction, and three-phase and multi-phase extraction. Mathematical models and comparative analyses of liquid membrane separations with different flow modes of contacting liquid phases are presented. A comparison of the processes of conventional and liquid membrane separations is carried out under the following assumptions: mass transfer is described by the traditional mass transfer equation; the equilibrium distribution coefficients of a component passing from one of the phases to another are constant. It is shown that, from the point of view of mass transfer driving forces, emulsion and film pertraction liquid membrane methods have advantages over the conventional conjugated extraction stripping method, when the mass-transfer efficiency of the extraction stage is significantly higher than the efficiency of the stripping stage. The comparison of the supported liquid membrane with conjugated extraction stripping showed that when mass-transfer rates on the extraction and stripping sides are different, the liquid membrane method is more efficient, while when they are equal to each other, both processes demonstrate the same results. The advantages and disadvantages of liquid membrane methods are discussed. The main disadvantages of liquid membrane methods—low throughput and complexity—can be overcome by using modified solvent extraction equipment to carry out liquid membrane separations.

The Latest Achievements of Liquid Membranes for Rare Earth Elements Recovery from Aqueous Solutions—A Mini Review

“…The stability of SLMs during long operation may be affected by various parameters, e.g., the nature of support and organic phase of the membrane, and conditions in which the membrane operates. Therefore, choosing the right separation method and optimal experimental conditions can be a challenge and, as noted by Kostanyan et al [20], "to select an appropriate method for solving the set separation problem, as well as for its optimal design, preliminary mathematical modeling is necessary". Recently, Tyagi et al [50] used an artificial neural network coupled with a genetic algorithm for modeling and optimization of the separation of neodymium ions with the use of a supported liquid membrane (with TOPO carrier) and, after the analysis of the effects of different input factors on the transport rate, determined the optimum set of parameters that provided the maximum extraction.…”

“…In general, in ELMs, the aqueous stripping phase (internal phase) is encapsulated (as microdroplets) in large droplets of a liquid membrane phase moving in the aqueous feed phase (external phase, containing an analyte, e.g., REE ions). However, systems are also known in which the feed phase is encapsulated (as microdroplets) in large droplets of the liquid membrane phase moving in a continuous stripping phase [20]. ELMs are double emulsions as they constitute either a water-in-oil-in-water (w/o/w) system or an oil-in-water-in-oil (o/w/o) system.…”

“…Differences in form between various LMs are quite significant, e.g., in the case of SLM, a porous material (polymer) is impregnated with the organic liquid membrane, while in ELM, the membrane solvent is emulsified. However, because of certain limitations associated with the use of LMs (e.g., SLM and ELM often exhibit low stability during application), the possibility of membrane modifications that would enable more efficient membrane processes, also on a larger scale, have been systematically investigated [19,20]. A type of liquid membrane whose composition and thickness can be easily modified is the polymer inclusion membrane (PIM), which, in addition to the polymer that forms the matrix of the membrane and the ions binding carriers, also usually contains a plasticizer that gives the membrane adequate plasticity.…”

Solvent Extraction of Au(III) by 2-ethylhexanol and Kinetic Modelling of the Facilitated Transport Across a Liquid Membrane

“…Indeed, the interest of scientists for the utilization of these membranes technologies on the recovery of metals or other pollutants still is alive as some recent publications also demonstrated. Several reviews about the general use of liquid membranes included: the transport of actinide elements using diglycolamides as carriers [6] and the application of membranes on the recovery of various elements [7][8][9][10], with mention to the use of Disclaimer/Publisher's Note: The statements, opinions, and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions, or products referred to in the content.…”

Treatment of Stainless Steel Rinse Waters Using Non-Dispersive Extraction and Strip Dispersion Membrane Technology

“…Using one or another type of liquid membrane operations, there were recent references to its applicability for the recovery and/or elimination of metals from different aqueous media [1][2][3][4]. Besides the above, most recent references to supported liquid membrane operation using permeation cells investigations have included the transport of Cr(VI) using organic solutions of the commercially available Cyanex 921 and Cyanex 923 phosphine oxides [5]; also, the transport of In(III) from HCl solutions has been investigated using the same methodology and the pseudo-protic ionic liquids TOAH + Cl − and TODAH + Cl − as carriers [6].…”