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3 pages, 166 KiB

Open AccessEditorial

Computational Approaches in Membrane Science and Engineering

by Alessio Fuoco, Giorgio De Luca, Elena Tocci and Johannes Carolus Jansen

Computation 2020, 8(2), 36; https://doi.org/10.3390/computation8020036 - 23 Apr 2020

Cited by 2 | Viewed by 2521

Abstract

Computational modelling and simulation form a consolidated branch in the multidisciplinary field of membrane science and technology [...] Full article

(This article belongs to the Special Issue Computational Design and Characterization of Membranes, Membrane Materials and Membrane Separation Processes)

Research

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16 pages, 6196 KiB

Open AccessArticle

Gas Transport in Mixed Matrix Membranes: Two Methods for Time Lag Determination

by Alessio Fuoco, Marcello Monteleone, Elisa Esposito, Rosaria Bruno, Jesús Ferrando-Soria, Emilio Pardo, Donatella Armentano and Johannes Carolus Jansen

Computation 2020, 8(2), 28; https://doi.org/10.3390/computation8020028 - 11 Apr 2020

Cited by 15 | Viewed by 4156

Abstract

The most widely used method to measure the transport properties of dense polymeric membranes is the time lag method in a constant volume/pressure increase instrument. Although simple and quick, this method provides only relatively superficial, averaged data of the permeability, diffusivity, and solubility [...] Read more.

The most widely used method to measure the transport properties of dense polymeric membranes is the time lag method in a constant volume/pressure increase instrument. Although simple and quick, this method provides only relatively superficial, averaged data of the permeability, diffusivity, and solubility of gas or vapor species in the membrane. The present manuscript discusses a more sophisticated computational method to determine the transport properties on the basis of a fit of the entire permeation curve, including the transient period. The traditional tangent method and the fitting procedure were compared for the transport of six light gases (H₂, He, O₂, N₂, CH₄, and CO₂) and ethane and ethylene in mixed matrix membranes (MMM) based on Pebax^®1657 and the metal–organic framework (MOF) Cu^II₂(S,S)-hismox·5H₂O. Deviations of the experimental data from the theoretical curve could be attributed to the particular MOF structure, with cavities of different sizes. The fitting procedure revealed two different effective diffusion coefficients for the same gas in the case of methane and ethylene, due to the unusual void morphology in the MOFs. The method was furthermore applied to mixed gas permeation in an innovative constant-pressure/variable-volume setup with continuous analysis of the permeate composition by an on-line mass-spectrometric residual gas analyzer. This method can provide the diffusion coefficient of individual gas species in a mixture, during mixed gas permeation experiments. Such information was previously inaccessible, and it will greatly enhance insight into the mixed gas transport in polymeric or mixed matrix membranes. Full article

(This article belongs to the Special Issue Computational Design and Characterization of Membranes, Membrane Materials and Membrane Separation Processes)

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9 pages, 5937 KiB

Open AccessFeature PaperArticle

Enzyme Immobilization on Polymer Membranes: A Quantum and Molecular Mechanics Study

by Francesco Petrosino, Stefano Curcio, Sudip Chakraborty and Giorgio De Luca

Computation 2019, 7(4), 56; https://doi.org/10.3390/computation7040056 - 28 Sep 2019

Cited by 27 | Viewed by 3478

Abstract

Adsorption of the phosphotriesterase on a polysulfone membrane surface was investigated in this paper through a double-scale computational approach. Surface charges of the enzyme, as well as membrane, were calculated at sub and nanoscale while protein adsorption was simulated at larger scale. Adsorption [...] Read more.

Adsorption of the phosphotriesterase on a polysulfone membrane surface was investigated in this paper through a double-scale computational approach. Surface charges of the enzyme, as well as membrane, were calculated at sub and nanoscale while protein adsorption was simulated at larger scale. Adsorption energies were calculated as a function of the enzyme–surface distance, and for each distance, several protein rotations were tested to find the most stable orientations of the macromolecule. The results of this model were useful in obtaining information about the adhesion of the enzyme and to give indications on the orientations of its binding site. Adsorption energies agreed with the literature data. Furthermore, the binding site of the immobilized phosphotriesterase was less accessible with respect to native enzymes due to the steric hindrance of the polymer surface; thus, a reduction of its efficiency is expected. The proposed methodology made use of fundamental quantities, calculated without resorting to adjustable or empirical parameters, providing basic outputs useful for ascertaining enzymatic catalysis rate. Full article

(This article belongs to the Special Issue Computational Design and Characterization of Membranes, Membrane Materials and Membrane Separation Processes)

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11 pages, 5034 KiB

Open AccessArticle

Molecular Dynamics of Water Embedded Carbon Nanocones: Surface Waves Observation

by Georgia Karataraki, Andreas Sapalidis, Elena Tocci and Anastasios Gotzias

Computation 2019, 7(3), 50; https://doi.org/10.3390/computation7030050 - 10 Sep 2019

Cited by 7 | Viewed by 5105

Abstract

We employed molecular dynamics simulations on the water solvation of conically shaped carbon nanoparticles. We explored the hydrophobic behaviour of the nanoparticles and investigated microscopically the cavitation of water in a conical confinement with different angles. We performed additional molecular dynamics simulations in [...] Read more.

We employed molecular dynamics simulations on the water solvation of conically shaped carbon nanoparticles. We explored the hydrophobic behaviour of the nanoparticles and investigated microscopically the cavitation of water in a conical confinement with different angles. We performed additional molecular dynamics simulations in which the carbon structures do not interact with water as if they were in vacuum. We detected a waving on the surface of the cones that resembles the shape agitations of artificial water channels and biological porins. The surface waves were induced by the pentagonal carbon rings (in an otherwise hexagonal network of carbon rings) concentrated near the apex of the cones. The waves were affected by the curvature gradients on the surface. They were almost undetected for the case of an armchair nanotube. Understanding such nanoscale phenomena is the key to better designed molecular models for membrane systems and nanodevices for energy applications and separation. Full article

(This article belongs to the Special Issue Computational Design and Characterization of Membranes, Membrane Materials and Membrane Separation Processes)

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14 pages, 6176 KiB

Open AccessArticle

Pressure-Induced Deformation of Pillar-Type Profiled Membranes and Its Effects on Flow and Mass Transfer

by Giuseppe Battaglia, Luigi Gurreri, Girolama Airò Farulla, Andrea Cipollina, Antonina Pirrotta, Giorgio Micale and Michele Ciofalo

Computation 2019, 7(2), 32; https://doi.org/10.3390/computation7020032 - 19 Jun 2019

Cited by 8 | Viewed by 3597

Abstract

In electro-membrane processes, a pressure difference may arise between solutions flowing in alternate channels. This transmembrane pressure (TMP) causes a deformation of the membranes and of the fluid compartments. This, in turn, affects pressure losses and mass transfer rates with respect to undeformed [...] Read more.

In electro-membrane processes, a pressure difference may arise between solutions flowing in alternate channels. This transmembrane pressure (TMP) causes a deformation of the membranes and of the fluid compartments. This, in turn, affects pressure losses and mass transfer rates with respect to undeformed conditions and may result in uneven flow rate and mass flux distributions. These phenomena were analyzed here for round pillar-type profiled membranes by integrated mechanical and fluid dynamics simulations. The analysis involved three steps: (1) A conservatively large value of TMP was imposed, and mechanical simulations were performed to identify the geometry with the minimum pillar density still able to withstand this TMP without collapsing (i.e., without exhibiting contacts between opposite membranes); (2) the geometry thus identified was subject to expansion and compression conditions in a TMP interval including the values expected in practical applications, and for each TMP, the corresponding deformed configuration was predicted; and (3) for each computed deformed configuration, flow and mass transfer were predicted by computational fluid dynamics. Membrane deformation was found to have important effects; friction and mass transfer coefficients generally increased in compressed channels and decreased in expanded channels, while a more complex behavior was obtained for mass transfer coefficients. Full article

(This article belongs to the Special Issue Computational Design and Characterization of Membranes, Membrane Materials and Membrane Separation Processes)

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14 pages, 9629 KiB

Open AccessArticle

Structure and Properties of High and Low Free Volume Polymers Studied by Molecular Dynamics Simulation

by Mikhail Mazo, Nikolay Balabaev, Alexandre Alentiev, Ivan Strelnikov and Yury Yampolskii

Computation 2019, 7(2), 27; https://doi.org/10.3390/computation7020027 - 31 May 2019

Cited by 14 | Viewed by 4159

Abstract

Using molecular dynamics, a comparative study was performed of two pairs of glassy polymers, low permeability polyetherimides (PEIs) and highly permeable Si-containing polytricyclononenes. All calculations were made with 32 independent models for each polymer. In both cases, the accessible free volume (AFV) increases [...] Read more.

Using molecular dynamics, a comparative study was performed of two pairs of glassy polymers, low permeability polyetherimides (PEIs) and highly permeable Si-containing polytricyclononenes. All calculations were made with 32 independent models for each polymer. In both cases, the accessible free volume (AFV) increases with decreasing probe size. However, for a zero-size probe, the curves for both types of polymers cross the ordinate in the vicinity of 40%. The size distribution of free volume in PEI and highly permeable polymers differ significantly. In the former case, they are represented by relatively narrow peaks, with the maxima in the range of 0.5–1.0 Å for all the probes from H₂ to Xe. In the case of highly permeable Si-containing polymers, much broader peaks are observed to extend up to 7–8 Å for all the gaseous probes. The obtained size distributions of free volume and accessible volume explain the differences in the selectivity of the studied polymers. The surface area of AFV is found for PEIs using Delaunay tessellation. Its analysis and the chemical nature of the groups that form the surface of free volume elements are presented and discussed. Full article

(This article belongs to the Special Issue Computational Design and Characterization of Membranes, Membrane Materials and Membrane Separation Processes)

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19 pages, 12680 KiB

Open AccessArticle

Numerical Simulation on Supercritical CO₂ Fluid Dynamics in a Hollow Fiber Membrane Contactor

by Hugo Valdés, Kevin Unda and Aldo Saavedra

Computation 2019, 7(1), 8; https://doi.org/10.3390/computation7010008 - 15 Jan 2019

Cited by 3 | Viewed by 4855

Abstract

This research answers the following question: What is the fluid dynamic behavior of a supercritical fluid (SCF) inside a membrane module? At this time, there is very little or no reported information that can provide an answer to this question. The research studies [...] Read more.

This research answers the following question: What is the fluid dynamic behavior of a supercritical fluid (SCF) inside a membrane module? At this time, there is very little or no reported information that can provide an answer to this question. The research studies related to the themes of supercritical CO₂ (SC-CO₂), hollow fiber membrane contactors (HFMCs), and numerical simulations have mainly reported on 2D simulations, but in this work, 3D profiles are presented. Simulations were performed based on the experimental results and other simulations, using the geometry of a commercial module. The results were mainly based on the different operating conditions and geometric dimensions. A mesh study was performed to ensure the mesh non-dependence of the results presented here. It was observed that the velocity profile developed at 10 mm from the wall of the supercritical CO₂ entrance pipe. A profile equilibrium around the fiber close to the entrance of the module was achieved in the experimental hollow fiber membrane contactor when compared to the case of the commercial hollow fiber membrane contactor. The results of this research provided a visualization of the boundary layer, which did not cover the entire fiber length. Finally, the results of this paper are interesting for technical applications and contribute to our understanding of the hydrodynamics of SCFs. Full article

(This article belongs to the Special Issue Computational Design and Characterization of Membranes, Membrane Materials and Membrane Separation Processes)

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Review

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26 pages, 5084 KiB

Open AccessReview

A Review on Computational Modeling Tools for MOF-Based Mixed Matrix Membranes

by Seda Keskin and Sacide Alsoy Altinkaya

Computation 2019, 7(3), 36; https://doi.org/10.3390/computation7030036 - 18 Jul 2019

Cited by 32 | Viewed by 5957

Abstract

Computational modeling of membrane materials is a rapidly growing field to investigate the properties of membrane materials beyond the limits of experimental techniques and to complement the experimental membrane studies by providing insights at the atomic-level. In this study, we first reviewed the [...] Read more.

Computational modeling of membrane materials is a rapidly growing field to investigate the properties of membrane materials beyond the limits of experimental techniques and to complement the experimental membrane studies by providing insights at the atomic-level. In this study, we first reviewed the fundamental approaches employed to describe the gas permeability/selectivity trade-off of polymer membranes and then addressed the great promise of mixed matrix membranes (MMMs) to overcome this trade-off. We then reviewed the current approaches for predicting the gas permeation through MMMs and specifically focused on MMMs composed of metal organic frameworks (MOFs). Computational tools such as atomically-detailed molecular simulations that can predict the gas separation performances of MOF-based MMMs prior to experimental investigation have been reviewed and the new computational methods that can provide information about the compatibility between the MOF and the polymer of the MMM have been discussed. We finally addressed the opportunities and challenges of using computational studies to analyze the barriers that must be overcome to advance the application of MOF-based membranes. Full article

(This article belongs to the Special Issue Computational Design and Characterization of Membranes, Membrane Materials and Membrane Separation Processes)

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