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Membranes
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Advances of Membrane Technology for Liquid Separation and Purification
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Advances of Membrane Technology for Liquid Separation and Purification

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

Deadline for manuscript submissions: closed (28 February 2022) | Viewed by 12645

Special Issue Editors

Dr. Jincai Su

E-Mail Website
Guest Editor
Ngee Ann Polytechnic, 535 Clementi Road, Singapore 599489, Singapore
Interests: applied membrane research; forward osmosis membrane and process development for liquid purification; ultrafiltration membrane for water treatment; membrane and system for liquid degassing
Prof. Dr. Neal Tai-Shung Chung

grade E-Mail Website
Guest Editor
Department of Chemical and Biomolecular Engineering, National University of Singapore, Singapore 119260, Singapore
Interests: membranes for water reuse; desalination; gas separation; biofuel separation; energy development and CO2 capture
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

In recent years, the focus of membrane research and development is seen shifting from maturing water-based separation (e.g., portable water, process water and wastewater treatment) to power generation, pharmaceutical production, food and beverage processing, and separations needed for manufacturing chemicals, electronics, fuels and a range of other liquid products. Behind this is the growing demands on reducing energy, saving resources and safe processing in various industrial processes. For liquid separation and purification, membrane materials and membrane devices are faced with new challenges of short lifetime, low productivity and low separation efficiency as a result of high operation temperature, in direct contact with harsh chemicals and strong solvents, extreme pH levels, and molecules to be separated with close chemical similarity, etc. Therefore, more robust and performing membrane materials and devices are critical for employing membrane technology for liquid separation and purification in commercial scale.

This special issue aims to collect research on membrane and membrane devices for liquid separation and purification to highlight the advances in membrane development, and to gain insight into the future direction and research focus in relevant fields.

Dr. Jincai Su
Prof. Dr. Neal Tai-Shung Chung
Guest Editors

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 submissions that pass pre-check are 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 2700 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 (4 papers)

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Research

21 pages, 11775 KiB  
Article
Pervaporation Membranes for Seawater Desalination Based on Geo–rGO–TiO2 Nanocomposites. Part 1: Microstructure Properties
by Subaer Subaer, Hamzah Fansuri, Abdul Haris, Misdayanti, Resky Irfanita, Imam Ramadhan, Yulprista Putri and Agung Setiawan
Membranes 2021, 11(12), 966; https://doi.org/10.3390/membranes11120966 - 08 Dec 2021
Cited by 5 | Viewed by 2746
Abstract
This is the first of two papers about the synthesis and microstructure properties of the Geo–rGO–TiO2 ternary nanocomposite, which was designed to suit the criteria of a pervaporation membrane for seawater desalination. The performance and capability of Geo–rGO–TiO2 as a seawater [...] Read more.
This is the first of two papers about the synthesis and microstructure properties of the Geo–rGO–TiO2 ternary nanocomposite, which was designed to suit the criteria of a pervaporation membrane for seawater desalination. The performance and capability of Geo–rGO–TiO2 as a seawater desalination pervaporation membrane are described in the second paper. A geopolymer made from alkali-activated metakaolin was utilized as a binder for the rGO-TiO2 nanocomposite. A modified Hummer’s method was used to synthesize graphene oxide (GO), and a hydrothermal procedure on GO produced reduced graphene oxide (rGO). The adopted approach yielded high-quality GO and rGO, based on Raman spectra results. The nanolayered structure of GO and rGO is revealed by Transmission Electron Microscopy (TEM) images. The Geo–rGO–TiO2 ternary nanocomposite was created by dispersing rGO nanosheets and TiO2 nanoparticles into geopolymer paste and stirring it for several minutes. The mixture was then cured in a sealed mold at 70 °C for one hour. After being demolded, the materials were kept for 28 days before being characterized. Fourier Transform Infrared (FTIR) and X-ray Diffraction (XRD) measurements revealed that the geopolymer matrix efficiently bonded the rGO and TiO2, creating nanocomposites. Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy (EDS) was used to examine the morphology of the outer layer and cross-sections of nanocomposites, and the results displayed that rGO were stacked on the surface as well as in the bulk of the geopolymer and will potentially function as nanochannels with a width of around 0.36 nm, while TiO2 NPs covered the majority of the geopolymer matrix, assisting in anti-biofouling of the membranes. The pores structure of the Geo–rGO–TiO2 were classified as micro–meso pores using the Brunauer–Emmet–Teller (BET) method, indicating that they are appropriate for use as pervaporation membranes. The mechanical strength of the membranes was found to be adequate to withstand high water pressure during the pervaporation process. The addition of rGO and TiO2 NPs was found to improve the hyropobicity of the Geo–rGO–TiO2 nanocomposite, preventing excessive seawater penetration into the membrane during the pervaporation process. The results of this study elucidate that the Geo–rGO–TiO2 nanocomposite has a lot of potential for application as a pervaporation membrane for seawater desalination because all of the initial components are widely available and inexpensive. Full article
(This article belongs to the Special Issue Advances of Membrane Technology for Liquid Separation and Purification)
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18 pages, 5265 KiB  
Article
CO2 Absorption Using Hollow Fiber Membrane Contactors: Introducing pH Swing Absorption (pHSA) to Overcome Purity Limitation
by Sayali Ramdas Chavan, Patrick Perré, Victor Pozzobon and Julien Lemaire
Membranes 2021, 11(7), 496; https://doi.org/10.3390/membranes11070496 - 30 Jun 2021
Cited by 6 | Viewed by 3366
Abstract
Recently, membrane contactors have gained more popularity in the field of CO2 removal; however, achieving high purity and competitive recovery for poor soluble gas (H2, N2, or CH4) remains elusive. Hence, a novel process for CO [...] Read more.
Recently, membrane contactors have gained more popularity in the field of CO2 removal; however, achieving high purity and competitive recovery for poor soluble gas (H2, N2, or CH4) remains elusive. Hence, a novel process for CO2 removal from a mixture of gases using hollow fiber membrane contactors is investigated theoretically and experimentally. A theoretical model is constructed to show that the dissolved residual CO2 hinders the capacity of the absorbent when it is regenerated. This model, backed up by experimental investigation, proves that achieving a purity > 99% without consuming excessive chemicals or energy remains challenging in a closed-loop system. As a solution, a novel strategy is proposed: the pH Swing Absorption which consists of manipulating the acido–basic equilibrium of CO2 in the absorption and desorption stages by injecting moderate acid and base amount. It aims at decreasing CO2 residual content in the regenerated absorbent, by converting CO2 into its ionic counterparts (HCO3− or CO32−) before absorption and improving CO2 degassing before desorption. Therefore, this strategy unlocks the theoretical limitation due to equilibrium with CO2 residual content in the absorbent and increases considerably the maximum achievable purity. Results also show the dependency of the performance on operating conditions such as total gas pressure and liquid flowrate. For N2/CO2 mixture, this process achieved a nitrogen purity of 99.97% with a N2 recovery rate of 94.13%. Similarly, for H2/CO2 mixture, a maximum H2 purity of 99.96% and recovery rate of 93.96% was obtained using this process. Moreover, the proposed patented process could potentially reduce energy or chemicals consumption. Full article
(This article belongs to the Special Issue Advances of Membrane Technology for Liquid Separation and Purification)
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11 pages, 2018 KiB  
Article
Study of Acid Whey Fouling after Protein Isolation Using Nanofiltration
by Marjana Simonič and Zorka Novak Pintarič
Membranes 2021, 11(7), 492; https://doi.org/10.3390/membranes11070492 - 30 Jun 2021
Cited by 6 | Viewed by 2025
Abstract
In this paper, nanofiltration (NF) of acid whey after isolation of proteins was studied. Two membranes were tested: NF-99 (Alfa Laval) and DL (Osmonic Desal). Based on previous measurements that determined the highest efficiency in separating lactic acid and lactose whey, the pH [...] Read more.
In this paper, nanofiltration (NF) of acid whey after isolation of proteins was studied. Two membranes were tested: NF-99 (Alfa Laval) and DL (Osmonic Desal). Based on previous measurements that determined the highest efficiency in separating lactic acid and lactose whey, the pH was adjusted to 3. First, the most appropriate transmembrane pressure (TMP) was determined based on the highest flux measured. The TMP range was 5–25 bar for the DL membrane and 10–30 bar for the NF-99 membrane. The temperature was kept at 4 °C using a thermostat. The mechanisms of membrane fouling were investigated. The Hermia models and the modified Tansel model were applied to study the fouling mechanism and to determine which membrane would foul earlier and more severely, respectively. The most suitable TMP was determined at 20 bar. Despite the 1.4 times higher flux of the sample at DL, the fouling rate was higher when NF-99 was used. The results showed that the Tansel model is suitable for predicting the fouling time of protein-isolated whey by nanofiltration. Full article
(This article belongs to the Special Issue Advances of Membrane Technology for Liquid Separation and Purification)
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12 pages, 4533 KiB  
Article
Lateral Degassing Method for Disposable Film-Chip Microfluidic Devices
by Suhee Park, Hyungseok Cho, Junhyeong Kim and Ki-Ho Han
Membranes 2021, 11(5), 316; https://doi.org/10.3390/membranes11050316 - 26 Apr 2021
Cited by 6 | Viewed by 3592
Abstract
It is critical to develop a fast and simple method to remove air bubbles inside microchannels for automated, reliable, and reproducible microfluidic devices. As an active degassing method, this study introduces a lateral degassing method that can be easily implemented in disposable film-chip [...] Read more.
It is critical to develop a fast and simple method to remove air bubbles inside microchannels for automated, reliable, and reproducible microfluidic devices. As an active degassing method, this study introduces a lateral degassing method that can be easily implemented in disposable film-chip microfluidic devices. This method uses a disposable film-chip microchannel superstrate and a reusable substrate, which can be assembled and disassembled simply by vacuum pressure. The disposable microchannel superstrate is readily fabricated by bonding a microstructured polydimethylsiloxane replica and a silicone-coated release polymeric thin film. The reusable substrate can be a plate that has no function or is equipped with the ability to actively manipulate and sense substances in the microchannel by an elaborately patterned energy field. The degassing rate of the lateral degassing method and the maximum available pressure in the microchannel equipped with lateral degassing were evaluated. The usefulness of this method was demonstrated using complex structured microfluidic devices, such as a meandering microchannel, a microvortex, a gradient micromixer, and a herringbone micromixer, which often suffer from bubble formation. In conclusion, as an easy-to-implement and easy-to-use technique, the lateral degassing method will be a key technique to address the bubble formation problem of microfluidic devices. Full article
(This article belongs to the Special Issue Advances of Membrane Technology for Liquid Separation and Purification)
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