Special Issue "Advances in Liquid Membrane-Based Separation"

A special issue of Membranes (ISSN 2077-0375). This special issue belongs to the section "Membrane Applications in Industry and Chemical Analysis".

Deadline for manuscript submissions: closed (15 May 2018)

Special Issue Editor

Guest Editor
Prof. Dr. Clàudia Fontàs

Department of Analytical Chemistry, The University of Girona, 17071 Girona, Spain
Website | E-Mail
Phone: +34 606800581
Fax: +34 972 418 150
Interests: separation processes based on functionalized membranes; supported liquid membranes; polymer inclusion membranes; membrane systems for the clean-up of natural waters and industrial wastewaters; physico-chemical and electrical characterization of membranes; environmental and industrial sampling and analysis

Special Issue Information

Dear Colleagues,

This Special Issue, entitled “Advances in Liquid Membrane-Based Separation”, is motivated by the growing interest in developing novel selective membranes to be used in separation processes. Liquid membranes (LM) possess attractive features, such as easy in terms of preparation and operation, and low in energy consumption, with a remarkable potential for low environmental impact and energy aspects. The selectivity of LM is easily increased with the use of an appropriate carrier, becoming functionalized membranes that can be very specific for the separation of target solutes. Separation systems based on LM have been successfully used for gas separations, recovery of valued or toxic metals, removal of organic compounds, and recovery biological systems. LMs are very versatile, and can be found in different configurations, such as supported liquid membranes (SLM) and membrane contactors, emulsion liquid membranes (ELM), or bulk liquid membranes (BLM). Additionally, the liquid membrane can be entrapped in a polymeric network, such as the case of polymer inclusion membranes (PIM). Liquid membrane science remains a fruitful and exciting area for research, with promise of offering many novel solutions to critical problems of separation systems. There is a need for both basic and applied research to enhance the possibilities of this technology.

Overall, this Special Issue is orientated to all the above-cited research topics, directed to the latest developments in liquid membrane based separation processes. Authors are welcome to submit original research papers, communications, and review articles. We are looking forward to your outstanding contribution for this Special Issue.

Prof. Dr. Clàudia Fontàs
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Membranes is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (6 papers)

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Research

Open AccessArticle Design of a Hollow Fiber Supported Liquid Membrane System for Zn Speciation in Natural Waters
Received: 15 August 2018 / Revised: 16 September 2018 / Accepted: 25 September 2018 / Published: 27 September 2018
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Abstract
A supported liquid membrane-hollow fiber system (HFSLM) has been developed to determine zinc speciation in aquatic environments. The liquid membrane consisted of an organic solution of bis-(2-ethylhexyl)phosphoric acid (D2EHPA) impregnated in the microporous of a polypropylene hollow fiber. The membrane contacted both the [...] Read more.
A supported liquid membrane-hollow fiber system (HFSLM) has been developed to determine zinc speciation in aquatic environments. The liquid membrane consisted of an organic solution of bis-(2-ethylhexyl)phosphoric acid (D2EHPA) impregnated in the microporous of a polypropylene hollow fiber. The membrane contacted both the donor solution, that contained the metal and the stripping solution, placed in the lumen of the hollow fiber, where the metal was preconcentrated. Different parameters affecting the Zn2+ transport efficiency have been evaluated such as the composition of both the donor and stripping solutions as well as the membrane phase. Extraction and transport efficiencies of free Zn(II) higher than 90% were obtained with a liquid membrane consisting of a 0.1 M D2EHPA solution in dodecane and a 0.1 M HNO3 solution as the stripping phase. The developed HFSLM was used to study the effect of different ligands (EDTA and citric acid) in the donor phase of Zn(II) transport and to investigate the selectivity of the membrane towards Zn when other metals were also present. Finally, the HFSLM system was successfully applied to estimate the free Zn(II) concentrations in three water samples from a mining area. Moreover, the HFSLM system facilitates the analytical determination of trace Zn(II) levels allowing the achievement of enrichment factors of around 700 in the stripping phase. Full article
(This article belongs to the Special Issue Advances in Liquid Membrane-Based Separation)
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Open AccessArticle Extraction Kinetics of As(V) by Aliquat-336 Using Asymmetric PVDF Hollow-Fiber Membrane Contactors
Received: 23 June 2018 / Revised: 19 July 2018 / Accepted: 24 July 2018 / Published: 2 August 2018
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Abstract
This work focuses on the study of the mass transfer of arsenic(V) through asymmetric polyvinylidene fluoride hollow-fiber membrane contactors using Aliquat-336 as an extractant. In the first part of this work, the fibers were prepared and characterized by SEM and by determining their [...] Read more.
This work focuses on the study of the mass transfer of arsenic(V) through asymmetric polyvinylidene fluoride hollow-fiber membrane contactors using Aliquat-336 as an extractant. In the first part of this work, the fibers were prepared and characterized by SEM and by determining their thickness and porosity. From SEM pictures, an asymmetric structure was obtained that was characterized by an inner sponge-like structure and outer finger-like structure with a pore radius and porosity about 0.11 µm and 80%, respectively. In the second part, the prepared fibers were used as membrane contactors for the study of mass transfer of arsenic(V), investigating the effect of several parameters such as pH, temperature, and initial concentration of the feed. The overall mass transfer coefficient of As(V) was around 6 × 10–6 cm/s. Full article
(This article belongs to the Special Issue Advances in Liquid Membrane-Based Separation)
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Open AccessArticle Applicability of a Supported Liquid Membrane in the Enrichment and Determination of Cadmium from Complex Aqueous Samples
Received: 21 March 2018 / Revised: 11 April 2018 / Accepted: 11 April 2018 / Published: 23 April 2018
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Abstract
A supported liquid membrane is developed for the separation of Cd from either high in salinity or acidity aqueous media. The membrane consisted of a durapore (polyvinylidene difluoride) polymeric support impregnated with a 0.5 M Aliquat 336 solution in decaline. The effect of [...] Read more.
A supported liquid membrane is developed for the separation of Cd from either high in salinity or acidity aqueous media. The membrane consisted of a durapore (polyvinylidene difluoride) polymeric support impregnated with a 0.5 M Aliquat 336 solution in decaline. The effect of carrier concentration, organic solvent and feed and receiving solutions on the metal permeability is studied. This system allows the effective transport of trace levels of Cd through the formation of CdCl42−, which is the predominant species responsible for the extraction process, in both NaCl and HCl solutions. The supported liquid membrane system in a hollow fibre configuration allows the enrichment and separation of trace levels of Cd from spiked seawater samples, facilitating the analytical determination of this toxic metal. Full article
(This article belongs to the Special Issue Advances in Liquid Membrane-Based Separation)
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Open AccessArticle Liquid Membranes as a Tool for Chemical Speciation of Metals in Natural Waters: Organic and Inorganic Complexes of Nickel
Received: 15 March 2018 / Revised: 3 April 2018 / Accepted: 3 April 2018 / Published: 15 April 2018
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Abstract
The different species of nickel present in natural waters exhibit different transport behaviour through bulk liquid membranes (BLMs). This fact has been used to design and optimise a separation/pre-concentration system applicable to separate labile and non-labile nickel fractions. A hydrazone derivative—1,2-cyclohexanedione bis-benzoyl-hydrazone (1,2-CHBBH) [...] Read more.
The different species of nickel present in natural waters exhibit different transport behaviour through bulk liquid membranes (BLMs). This fact has been used to design and optimise a separation/pre-concentration system applicable to separate labile and non-labile nickel fractions. A hydrazone derivative—1,2-cyclohexanedione bis-benzoyl-hydrazone (1,2-CHBBH) dissolved in toluene/dimethyl formamide (2% DMF)—was used as a chemical carrier of nickel species, from an aqueous source solution (sample) to a receiving acidic solution. Both chemical and hydrodynamic conditions controlling the transport system were studied and optimised. Under optimum conditions, variations in the transport of nickel ions as a function of organic (humic acids) and inorganic (chloride ions) ligands were studied. Relationships between the permeability coefficient (P) or recovery efficiency (%R) and the concentrations of ligands and nickel species were analysed using Winhumic V software. A negative correlation between P and the concentration of organic nickel complexes was found, suggesting that only labile nickel species are transported through the liquid membrane, with non-labile complexes remaining in the water sample; allowing for their separation and subsequent quantification in natural waters. Full article
(This article belongs to the Special Issue Advances in Liquid Membrane-Based Separation)
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Open AccessArticle Gas Transport in Glassy Polymers: Prediction of Diffusional Time Lag
Received: 29 December 2017 / Revised: 26 January 2018 / Accepted: 1 February 2018 / Published: 3 February 2018
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Abstract
The transport of gases in glassy polymeric membranes has been analyzed by means of a fundamental approach based on the nonequilibrium thermodynamic model for glassy polymers (NET-GP) that considers the penetrant chemical potential gradient as the actual driving force of the diffusional process. [...] Read more.
The transport of gases in glassy polymeric membranes has been analyzed by means of a fundamental approach based on the nonequilibrium thermodynamic model for glassy polymers (NET-GP) that considers the penetrant chemical potential gradient as the actual driving force of the diffusional process. The diffusivity of a penetrant is thus described as the product of a purely kinetic quantity, the penetrant mobility, and a thermodynamic factor, accounting for the chemical potential dependence on its concentration in the polymer. The NET-GP approach, and the nonequilibrium lattice fluid (NELF) model in particular, describes the thermodynamic behavior of penetrant/polymer mixtures in the glassy state, at each pressure or composition. Moreover, the mobility is considered to follow a simple exponential dependence on penetrant concentration, as typically observed experimentally, using only two adjustable parameters, the infinite dilution penetrant mobility L10 and the plasticization factor β, both determined from the analysis of the dependence of steady state permeability on upstream pressure. The available literature data of diffusional time lag as a function of penetrant upstream pressure has been reviewed and compared with model predictions, obtained after the values of the two model parameters (L10 and β), have been conveniently determined from steady state permeability data. The model is shown to be able to describe very accurately the experimental time lag behaviors for all penetrant/polymer pairs inspected, including those presenting an increasing permeability with increasing upstream pressure. The model is thus more appropriate than the one based on Dual Mode Sorption, which usually provides an unsatisfactory description of time lag and required an ad hoc modification. Full article
(This article belongs to the Special Issue Advances in Liquid Membrane-Based Separation)
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Open AccessArticle The Effect of Surface Confined Gold Nanoparticles in Blocking the Extraction of Nitrate by PVC-Based Polymer Inclusion Membranes Containing Aliquat 336 as the Carrier
Received: 1 January 2018 / Revised: 18 January 2018 / Accepted: 22 January 2018 / Published: 25 January 2018
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Abstract
Clusters of gold nanoparticles (AuNPs) formed on the surface of PVC-based polymer inclusion membranes (PIMs) with a liquid phase containing Aliquat 336 as the carrier and in some cases 1-dodecanol or 2-nitrophenol octyl ether as plasticizers were found to inhibit the extraction of [...] Read more.
Clusters of gold nanoparticles (AuNPs) formed on the surface of PVC-based polymer inclusion membranes (PIMs) with a liquid phase containing Aliquat 336 as the carrier and in some cases 1-dodecanol or 2-nitrophenol octyl ether as plasticizers were found to inhibit the extraction of nitrate by the PIMs. This observation was based on gradually increasing the mass of AuNPs on the membrane surface and testing the ability of the membrane to extract nitrate after each increase. In this way, it was possible to determine the so-called “critical AuNP masses” at which the studied membranes ceased to extract nitrate. On the basis of these results, it can be hypothesized that the surfaces of these PIMs are not homogeneous with respect to the distribution of their membrane liquid phases, which are present only at certain sites. Extraction takes place only at these sites, and at the “critical AuNP mass” of a PIM, all these extraction sites are blocked and the membrane loses its ability to extract. Full article
(This article belongs to the Special Issue Advances in Liquid Membrane-Based Separation)
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