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17 pages, 8351 KiB

Open AccessArticle

Impact of Silver-Decorated Graphene Oxide (Ag-GO) towards Improving the Characteristics of Nanohybrid Polysulfone Membranes

by Nur Syahirah Suhalim, Norherdawati Kasim, Ebrahim Mahmoudi, Intan Juliana Shamsudin, Nor Laili-Azua Jamari and Fathiah Mohamed Zuki

Membranes 2023, 13(6), 602; https://doi.org/10.3390/membranes13060602 - 15 Jun 2023

Cited by 5 | Viewed by 1799

Abstract

The utilization of membranes has been extensively employed in the treatment of water and wastewater. Membrane fouling, attributed to the hydrophobic nature of membranes, constitutes a noteworthy concern in the realm of membrane separation. The mitigation of fouling can be achieved through the [...] Read more.

The utilization of membranes has been extensively employed in the treatment of water and wastewater. Membrane fouling, attributed to the hydrophobic nature of membranes, constitutes a noteworthy concern in the realm of membrane separation. The mitigation of fouling can be achieved through the modification of membrane characteristics, including but not limited to hydrophilicity, morphology, and selectivity. In this study, a nanohybrid polysulfone (PSf) membrane embedded with silver–graphene oxide (Ag-GO) was fabricated to overcome problems related to biofouling. The embedment of Ag-GO nanoparticles (NPs) is the aim towards producing membranes with antimicrobial properties. The fabricated membranes at different compositions of NPs (0 wt%, 0.3 wt%, 0.5 wt%, and 0.8 wt%) are denoted as M0, M1, M2, and M3, respectively. These PSf/Ag-GO membranes were characterized using FTIR, water contact angle (WCA) goniometer, FESEM, and salt rejection. The additions of GO significantly improved the hydrophilicity of PSf membranes. An additional OH peak at 3380.84 cm⁻¹ of the nanohybrid membrane from FTIR spectra may be related to hydroxyl (-OH) groups of GO. The WCA of the fabricated membranes decreased from 69.92° to 54.71°, which confirmed the improvement in its hydrophilicity. In comparison to the pure PSf membrane, the morphology of the finger-like structure of the fabricated nanohybrid membrane slightly bent with a larger bottom part. Among the fabricated membranes, M2 achieved the highest iron (Fe) removal, up to 93%. This finding proved that the addition of 0.5 wt% Ag-GO NPs enhanced the membrane water permeability together with its performance of ionic solute removal (Fe²⁺) from synthetic groundwater. In conclusion, embedding a small amount of Ag-GO NPs successfully improved the hydrophilicity of PSf membranes and was able to achieve high removal of Fe at 10–100 mg L⁻¹ towards purification of groundwater for safe drinking water. Full article

(This article belongs to the Special Issue Membrane Science towards Sustainable Development Goals (SDGs))

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24 pages, 4789 KiB

Open AccessArticle

Magnesium Oxide Nanoparticles for the Adsorption of Pentavalent Arsenic from Water: Effects of Calcination

by Shaymala Mehanathan, Juhana Jaafar, Atikah Mohd Nasir, Ahmad Fauzi Ismail, Takeshi Matsuura, Mohd Hafiz Dzarfan Othman, Mukhlis A. Rahman and Norhaniza Yusof

Membranes 2023, 13(5), 475; https://doi.org/10.3390/membranes13050475 - 28 Apr 2023

Cited by 9 | Viewed by 2810

Abstract

The occurrence of heavy metal ions in water is intractable, and it has currently become a serious environmental issue to deal with. The effects of calcining magnesium oxide at 650 °C and the impacts on the adsorption of pentavalent arsenic from water are [...] Read more.

The occurrence of heavy metal ions in water is intractable, and it has currently become a serious environmental issue to deal with. The effects of calcining magnesium oxide at 650 °C and the impacts on the adsorption of pentavalent arsenic from water are reported in this paper. The pore nature of a material has a direct impact on its ability to function as an adsorbent for its respective pollutant. Calcining magnesium oxide is not only beneficial in enhancing its purity but has also been proven to increase the pore size distribution. Magnesium oxide, as an exceptionally important inorganic material, has been widely studied in view of its unique surface properties, but the correlation between its surface structure and physicochemical performance is still scarce. In this paper, magnesium oxide nanoparticles calcined at 650 °C are assessed to remove the negatively charged arsenate ions from an aqueous solution. The increased pore size distribution was able to give an experimental maximum adsorption capacity of 115.27 mg/g with an adsorbent dosage of 0.5 g/L. Non-linear kinetics and isotherm models were studied to identify the adsorption process of ions onto the calcined nanoparticles. From the adsorption kinetics study, the non-linear pseudo-first order showed an effective adsorption mechanism, and the most suitable adsorption isotherm was the non-linear Freundlich isotherm. The resulting R² values of other kinetic models, namely Webber-Morris and Elovich, were still below those of the non-linear pseudo-first-order model. The regeneration of magnesium oxide in the adsorption of negatively charged ions was determined by making comparisons between fresh and recycled adsorbent that has been treated with a 1 M NaOH solution. Full article

(This article belongs to the Special Issue Membrane Science towards Sustainable Development Goals (SDGs))

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21 pages, 8695 KiB

Open AccessArticle

Synthesis and Characterisation of Self-Cleaning TiO₂/PES Mixed Matrix Membranes in the Removal of Humic Acid

by Yan Kee Poon, Siti Kartini Enche Ab Rahim, Qi Hwa Ng, Peng Yong Hoo, Nur Yasmin Abdullah, Amira Nasib and Norazharuddin Shah Abdullah

Membranes 2023, 13(4), 373; https://doi.org/10.3390/membranes13040373 - 24 Mar 2023

Cited by 8 | Viewed by 1797

Abstract

Membrane application is widespread in water filtration to remove natural organic matter (NOM), especially humic acid. However, there is a significant concern in membrane filtration, which is fouling, which will cause a reduction in the membrane life span, a high energy requirement, and [...] Read more.

Membrane application is widespread in water filtration to remove natural organic matter (NOM), especially humic acid. However, there is a significant concern in membrane filtration, which is fouling, which will cause a reduction in the membrane life span, a high energy requirement, and a loss in product quality. Therefore, the effect of a TiO₂/PES mixed matrix membrane on different concentrations of TiO₂ photocatalyst and different durations of UV irradiation was studied in removing humic acid to determine the anti-fouling and self-cleaning effects. The TiO₂ photocatalyst and TiO₂/PES mixed matrix membrane synthesised were characterised using attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray powder diffraction (XRD), scanning electron microscope (SEM), contact angle, and porosity. The performances of TiO₂/PES membranes of 0 wt.%, 1 wt.%, 3 wt.%, and 5 wt.% were evaluated via a cross-flow filtration system regarding anti-fouling and self-cleaning effects. After that, all the membranes were irradiated under UV for either 2, 10, or 20 min. A TiO₂/PES mixed matrix membrane of 3 wt.% was proved to have the best anti-fouling and self-cleaning effect with improved hydrophilicity. The optimum duration for UV irradiation of the TiO₂/PES mixed matrix membrane was 20 min. Furthermore, the fouling behaviour of mixed matrix membranes was fitted to the intermediate blocking model. Adding TiO₂ photocatalyst into the PES membrane enhanced the anti-fouling and self-cleaning properties. Full article

(This article belongs to the Special Issue Membrane Science towards Sustainable Development Goals (SDGs))

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21 pages, 3922 KiB

Open AccessArticle

Polydimethylsiloxane/Magnesium Oxide Nanosheet Mixed Matrix Membrane for CO₂ Separation Application

by Muhd Izzudin Fikry Zainuddin, Abdul Latif Ahmad and Meor Muhammad Hafiz Shah Buddin

Membranes 2023, 13(3), 337; https://doi.org/10.3390/membranes13030337 - 14 Mar 2023

Cited by 8 | Viewed by 2702

Abstract

Carbon dioxide (CO₂) concentration is now 50% higher than in the preindustrial period and efforts to reduce CO₂ emission through carbon capture and utilization (CCU) are blooming. Membranes are one of the attractive alternatives for such application. In this study, [...] Read more.

Carbon dioxide (CO₂) concentration is now 50% higher than in the preindustrial period and efforts to reduce CO₂ emission through carbon capture and utilization (CCU) are blooming. Membranes are one of the attractive alternatives for such application. In this study, a rubbery polymer polydimethylsiloxane (PDMS) membrane is incorporated with magnesium oxide (MgO) with a hierarchically two-dimensional (2D) nanosheet shape for CO₂ separation. The average thickness of the synthesized MgO nanosheet in this study is 35.3 ± 1.5 nm. Based on the pure gas separation performance, the optimal loading obtained is at 1 wt.% where there is no observable significant agglomeration. CO₂ permeability was reduced from 2382 Barrer to 1929 Barrer while CO₂/N₂ selectivity increased from only 11.4 to 12.7, and CO₂/CH₄ remained relatively constant when the MMM was operated at 2 bar and 25 °C. Sedimentation of the filler was observed when the loading was further increased to 5 wt.%, forming interfacial defects on the bottom side of the membrane and causing increased CO₂ gas permeability from 1929 Barrer to 2104 Barrer as compared to filler loading at 1 wt.%, whereas the CO₂/N₂ ideal selectivity increased from 12.1 to 15.0. Additionally, this study shows that there was no significant impact of pressure on separation performance. There was a linear decline of CO₂ permeability with increasing upstream pressure while there were no changes to the CO₂/N₂ and CO₂/CH₄ selectivity. Full article

(This article belongs to the Special Issue Membrane Science towards Sustainable Development Goals (SDGs))

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17 pages, 4111 KiB

Open AccessArticle

Polydimethylsiloxane (PDMS) Membrane for Separation of Soluble Toluene by Pervaporation Process

by Salam H. Rasheed, Salah S. Ibrahim, Qusay F. Alsalhy and Hasan Sh. Majdi

Membranes 2023, 13(3), 289; https://doi.org/10.3390/membranes13030289 - 28 Feb 2023

Cited by 3 | Viewed by 3032

Abstract

A commercial polydimethylsiloxane (PDMS) membrane was employed to separate the soluble toluene compounds (C₇H₈) from an aqueous solution via the pervaporation (PV) process. The performance and the efficacy of the PDMS PV membrane were evaluated through the estimation of [...] Read more.

A commercial polydimethylsiloxane (PDMS) membrane was employed to separate the soluble toluene compounds (C₇H₈) from an aqueous solution via the pervaporation (PV) process. The performance and the efficacy of the PDMS PV membrane were evaluated through the estimation of the permeation flux and separation factor under various operating parameters. The response surface method (RSM) built in the Minitab-18 software was used for the design of the experiment in this study, and the responses of the permeation flux and the separation factor were analyzed and optimized based on the operating conditions. A nonlinear regression analysis was applied to the experimental output and input, and as a result, a quadratic equation model with parameters interactions was obtained as mathematical expressions to predict the permeation flux and separation factor. At the optimal conditions of temperature 30 °C, initial toluene concentration 500 ppm, and feed flowrate 3.5 L/min, the toluene permeation flux and separation factor were 125.855 g/m²·h and 1080, respectively. The feed concentration was the most impactful and significant in the improvement of the permeation flux and separation factor of the PDMS membrane. Full article

(This article belongs to the Special Issue Membrane Science towards Sustainable Development Goals (SDGs))

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24 pages, 11294 KiB

Open AccessArticle

Surface Modification of UiO-66 on Hollow Fibre Membrane for Membrane Distillation

by Noor Fadilah Yusof, Amirul Afiat Raffi, Nur Zhatul Shima Yahaya, Khairul Hamimah Abas, Mohd Hafiz Dzarfan Othman, Juhana Jaafar and Mukhlis A. Rahman

Membranes 2023, 13(3), 253; https://doi.org/10.3390/membranes13030253 - 21 Feb 2023

Cited by 5 | Viewed by 2742

Abstract

The hydrophobicity of metal–organic frameworks (MOFs) is critical in enhancing the separation process in membrane distillation. Herein, a new superhydrophobic University of Oslo 66 (UiO-66) MOFs was successfully constructed on the top of alumina hollow fibre (AHF) membrane for desalination purposes. The fabrication [...] Read more.

The hydrophobicity of metal–organic frameworks (MOFs) is critical in enhancing the separation process in membrane distillation. Herein, a new superhydrophobic University of Oslo 66 (UiO-66) MOFs was successfully constructed on the top of alumina hollow fibre (AHF) membrane for desalination purposes. The fabrication methodology of the membrane involved in situ growth of pure crystalline UiO-66 on top of AHF and post-synthetic modification by fluorosilane grafting. The resultant membrane was characterised to study the physicochemical properties of the pristine and modified membrane. A superhydrophobic UiO-66 with a contact angle of 163.6° and high liquid entry pressure was obtained by introducing a highly branched fluorocarbon chain while maintaining its crystallinity. As a result, the modified membrane achieved 14.95 L/m²∙h water flux and 99.9% NaCl rejection with low energy consumption in the direct contact membrane distillation process. Furthermore, the high surface energy contributed by UiO-66 is maximised to produce the maximum number of accessible sites for the grafting process. The synergistic effect of surface hydrophobicity and porous UiO-66 membrane in trapping water vapour shows great potential for desalination application. Full article

(This article belongs to the Special Issue Membrane Science towards Sustainable Development Goals (SDGs))

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18 pages, 9904 KiB

Open AccessArticle

Effect of Methacrylic Acid Monomer on UV-Grafted Polyethersulfone Forward Osmosis Membrane

by S. N. S. A. Aziz, M. N. Abu Seman, S. M. Saufi, A. W. Mohammad and M. Khayet

Membranes 2023, 13(2), 232; https://doi.org/10.3390/membranes13020232 - 15 Feb 2023

Cited by 2 | Viewed by 2089

Abstract

UV irradiation is one of the procedures that has been considered for membrane surface graft polymerization. It is commonly utilized for enhancing the wettability of polyethersulfone (PES) membranes. In this research study, the monomer methacrylic acid (MAA) was used for the UV grafting [...] Read more.

UV irradiation is one of the procedures that has been considered for membrane surface graft polymerization. It is commonly utilized for enhancing the wettability of polyethersulfone (PES) membranes. In this research study, the monomer methacrylic acid (MAA) was used for the UV grafting process of a commercial NF2 PES membrane for the preparation of a forward osmosis (FO) membrane. Three different monomer concentrations and three different UV irradiation times were considered. The intrinsic characteristics of both the surface-modified and pristine membranes were determined via a non-pressurized test method. Compared to the NF2 PES, the surface of the modified membranes was rendered more hydrophilic, as the measured water contact angle was reduced considerably from 65° to 32–58°. The membrane surface modification was also confirmed by the data collected from other techniques, such as atomic force microscopy (AFM), field emission-scanning electron microscope (FESEM) and Fourier-transform infrared spectroscopy–attenuated total reflectance (FTIR–ATR). Additionally, the modified membranes exhibited a greater water permeate flux (J_w) compared to the NF2 PES membrane. In this study, the water permeability (A), solute permeability (B) and structural parameter (S) were determined via a two-stage FO non-pressurized test method, changing the membrane orientation. Compared to the FO pressurized test, smaller S values were obtained with significantly high A and B values for the two non-pressurized tests. The adopted method in the current study is more adequate for determining the intrinsic characteristics of FO membranes. Full article

(This article belongs to the Special Issue Membrane Science towards Sustainable Development Goals (SDGs))

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13 pages, 2471 KiB

Open AccessArticle

A Novel Tri-Functionality pH-Magnetic-Photocatalytic Hybrid Organic-Inorganic Polyoxometalates Augmented Microspheres for Polluted Water Treatment

by Li Ying Yee, Qi Hwa Ng, Siti Kartini Enche Ab Rahim, Peng Yong Hoo, Pei Thing Chang, Abdul Latif Ahmad, Siew Chun Low and Siew Hoong Shuit

Membranes 2023, 13(2), 174; https://doi.org/10.3390/membranes13020174 - 31 Jan 2023

Cited by 2 | Viewed by 1673

Abstract

The severe water pollution from effluent dyes threatens human health. This study created pH-magnetic-photocatalytic polymer microspheres to conveniently separate the photocatalyst nanoparticles from the treated water by applying an external magnetic field. While fabricating magnetic nanoparticles’ (MNPs) microspheres, incorporating 0.5 wt.% iron oxide [...] Read more.

The severe water pollution from effluent dyes threatens human health. This study created pH-magnetic-photocatalytic polymer microspheres to conveniently separate the photocatalyst nanoparticles from the treated water by applying an external magnetic field. While fabricating magnetic nanoparticles’ (MNPs) microspheres, incorporating 0.5 wt.% iron oxide (Fe₃O₄) showed the best magnetophoretic separation ability, as all the MNPs microspheres were attracted toward the external magnet. Subsequently, hybrid organic–inorganic polyoxometalates (HPOM), a self-synthesized photocatalyst, were linked with the functionalized magnetic nanoparticles (f-MNPs) to prepare augmented magnetic-photocatalytic microspheres. The photodegradation dye removal efficiency of the augmented magnetic-photocatalytic microspheres (f-MNPs-HPOM) was then compared with that of the commercial titanium dioxide (TiO₂) photocatalyst (f-MNPs-TiO₂). Results showed that f-MNPs-HPOM microspheres with 74 ± 0.7% photocatalytic removal efficiency better degraded methylene orange (MO) than f-MNPs-TiO₂ (70 ± 0.8%) at an unadjusted pH under UV-light irradiation for 90 min. The excellent performance was mainly attributed to the lower band-gap energy of HPOM (2.65 eV), which required lower energy to be photoactivated under UV light. The f-MNPs-HPOM microspheres demonstrated excellent reusability and stability in the photo-decolorization of MO, as the microspheres retained nearly the same removal percentage throughout the three continuous cycles. The degradation rate was also found to follow the pseudo-first-order kinetics. Furthermore, f-MNPs-HPOM microspheres were pH-responsive in the photodegradation of MO and methylene blue (MB) at pH 3 (acidic) and pH 9 (alkaline). Overall, it was demonstrated that using HPOM photocatalysts in the preparation of magnetic-photocatalytic microspheres resulted in better dye degradation than TiO₂ photocatalysts. Full article

(This article belongs to the Special Issue Membrane Science towards Sustainable Development Goals (SDGs))

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17 pages, 6712 KiB

Open AccessArticle

Hybrid Inorganic Organic PSF/Hap Dual-Layer Hollow Fibre Membrane for the Treatment of Lead Contaminated Water

by Sumarni Mansur, Mohd Hafiz Dzarfan Othman, Nurul Jannah Ismail, Siti Hamimah Sheikh Abdul Kadir, Mohd Hafiz Puteh, Huda Abdullah, Juhana Jaafar, Mukhlis A. Rahman, Tutuk Djoko Kusworo, Ahmad Fauzi Ismail and Abdul Latif Ahmad

Membranes 2023, 13(2), 170; https://doi.org/10.3390/membranes13020170 - 30 Jan 2023

Cited by 2 | Viewed by 1704

Abstract

Lead (Pb) exposure can be harmful to public health, especially through drinking water. One of the promising treatment methods for lead contaminated water is the adsorption-filtration method. To ensure the cost-effectiveness of the process, naturally derived adsorbent shall be utilised. In this study, [...] Read more.

Lead (Pb) exposure can be harmful to public health, especially through drinking water. One of the promising treatment methods for lead contaminated water is the adsorption-filtration method. To ensure the cost-effectiveness of the process, naturally derived adsorbent shall be utilised. In this study, hydroxyapatite particles, Ca₁₀(PO₄)₆(OH)₂ (HAP) derived from waste cockle shell, were incorporated into the outer layer of polysulfone/HAP (PSf/HAP) dual-layer hollow fibre (DLHF) membrane to enhance the removal of lead from the water source due to its hydrophilic nature and excellent adsorption capacity. The PSf/HAP DLHF membranes at different HAP loadings in the outer layer (0, 10, 20, 30 and 40 wt%) were fabricated via the co-extrusion phase inversion technique. The performance of the DLHF membranes was evaluated in terms of pure water flux, permeability and adsorption capacity towards lead. The results indicated that the HAP was successfully incorporated into the outer layer of the membrane, as visibly confirmed by microscopic analysis. The trend was towards an increase in pure water flux, permeability and lead adsorption capacity as the HAP loading increased to the optimum loading of 30 wt%. The optimized DLHF membrane displayed a reduced water contact angle by 95%, indicating its improved surface hydrophilicity, which positively affects the pure water flux and permeability of the membrane. Furthermore, the DLHF membrane possessed the highest lead adsorption capacity, 141.2 mg/g. The development of a hybrid inorganic–organic DLHF membrane via the incorporation of the naturally derived HAP in the outer layer is a cost-effective approach to treat lead contaminated water. Full article

(This article belongs to the Special Issue Membrane Science towards Sustainable Development Goals (SDGs))

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13 pages, 2367 KiB

Open AccessArticle

Prediction of CO₂ Permeance across ZIF-L@PDMS/PES Composite Membrane

by Meor Muhammad Hafiz Shah Buddin, Abdul Latif Ahmad and Muhd Izzudin Fikry Zainuddin

Membranes 2023, 13(2), 134; https://doi.org/10.3390/membranes13020134 - 19 Jan 2023

Cited by 3 | Viewed by 1974

Abstract

The current work predicted the permeance of CO₂ across a ZIF-L@PDMS/PES composite membrane using two different models. The membrane was fabricated by dipping a PES hollow fiber membrane in a coating solution made using PDMS that contained ZIF-L. First, flat sheet ZIF-L@PDMS [...] Read more.

The current work predicted the permeance of CO₂ across a ZIF-L@PDMS/PES composite membrane using two different models. The membrane was fabricated by dipping a PES hollow fiber membrane in a coating solution made using PDMS that contained ZIF-L. First, flat sheet ZIF-L@PDMS membranes were fabricated to verify the role of ZIF-L on the gas separation performance of the membrane. Based on the data, the presence of ZIF-L in the PDMS matrix allowed enhancement of both permeability and selectivity of CO₂, where the maximum value was obtained at 1 wt% of ZIF-L. The performance of ZIF-L@PDMS layer, as a function of ZIF-L loading, was well-predicted by the Cussler model. Such information was then used to model the CO₂ permeance across ZIF-L@PDMS/PES composite membrane via the correction factor, which was introduced in the resistance in series model. This work discovered that the model must consider the penetration depth and the inorganic loading (in the case of ZIF-L@PDMS/PES). The error between the predicted CO₂ permeance and the experimental results was found to be minimal. Full article

(This article belongs to the Special Issue Membrane Science towards Sustainable Development Goals (SDGs))

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23 pages, 2627 KiB

Open AccessArticle

Novel Organic Solvent Nanofiltration Approaches for Microbial Biosurfactants Downstream Processing

by Miguel Figueiredo Nascimento, Petar Keković, Isabel A. C. Ribeiro, Nuno Torres Faria and Frederico Castelo Ferreira

Membranes 2023, 13(1), 81; https://doi.org/10.3390/membranes13010081 - 9 Jan 2023

Cited by 9 | Viewed by 3564

Abstract

Glycolipid biosurfactants are the most prominent group of microbial biosurfactants, comprising rhamnolipids, sophorolipids and mannosylerythritol lipids (MELs). Usually, large amounts of hydrophobic substrates (e.g., vegetable oils) are used to achieve high titers (~200 g/L) of a crude product of low purity at values [...] Read more.

Glycolipid biosurfactants are the most prominent group of microbial biosurfactants, comprising rhamnolipids, sophorolipids and mannosylerythritol lipids (MELs). Usually, large amounts of hydrophobic substrates (e.g., vegetable oils) are used to achieve high titers (~200 g/L) of a crude product of low purity at values limited to 50–60%, contaminated with unconsumed triacylglycerol and residual free fatty acids and monoacylglycerides. The methods reported for the removal of these contaminants use a mixture of organic solvents, compromising solvent recyclability and increasing final process costs. This study reports, for the first time, an innovative downstream method for MELs, in which 90% of the triacylglycerols are separated from the crude MEL mixture in a first stage and the other lipid derivatives (free fatty acids, mono- and diacylglycerols) are removed by organic solvent nanofiltration (OSN). Three commercially available membranes (GMT-oNF-2, PuraMEm-600 and DuramMem-500) and several homemade membranes, casted from 22, 24 or 26% (w/v) polybenzimidazole (PBI) solutions, were assessed for crude MELs purification by diafiltration. A final purity of 87–90% in the MELs was obtained by filtering two diavolumes of methanol or ethyl acetate solutions through a PBI 26% membrane, resulting in MELs losses of 14.7 ± 6.1% and 15.3 ± 2.2%, respectively. Higher biosurfactant purities can be archived using the PBI 26% membrane at higher DV, but at the cost of higher product losses. Namely, in MeOH, the use of 6 DV leads to losses of 32% for MELs and 18% for sophorolipids. To obtain MELs at reagent grade with purities equal or higher than 97%, a two-sequential cascade filtration approach was implemented using the commercial membrane, GMT-oNF. In such a process, MELs with 98% purity was obtained at the cost of 11.6% MELs losses. Finally, decoloration, important in some applications, was successfully assessed using activated carbon. Overall, this study reports a unique solution for microbial biosurfactants production with minimal product losses, enabling solvent recycling and potentially reducing costs. Full article

(This article belongs to the Special Issue Membrane Science towards Sustainable Development Goals (SDGs))

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15 pages, 2578 KiB

Open AccessArticle

A Comparison between Various Polymeric Membranes for Oily Wastewater Treatment via Membrane Distillation Process

by Dharshini Mohanadas, Puteri Mimie Isma Nordin, Rosiah Rohani, Nur Syafiqah Farhanah Dzulkharnien, Abdul Wahab Mohammad, Peer Mohamed Abdul and Suriani Abu Bakar

Membranes 2023, 13(1), 46; https://doi.org/10.3390/membranes13010046 - 29 Dec 2022

Cited by 5 | Viewed by 2241

Abstract

Oily wastewater (OW) is detrimental towards the environment and human health. The complex composition of OW needs an advanced treatment, such as membrane technology. Membrane distillation (MD) gives the highest rejection percentage of pollutants in wastewater, as the membrane only allows the vapor [...] Read more.

Oily wastewater (OW) is detrimental towards the environment and human health. The complex composition of OW needs an advanced treatment, such as membrane technology. Membrane distillation (MD) gives the highest rejection percentage of pollutants in wastewater, as the membrane only allows the vapor to pass its microporous membrane. However, the commercial membranes on the market are less efficient in treating OW, as they are prone to fouling. Thus, the best membrane must be identified to treat OW effectively. This study tested and compared the separation performance of different membranes, comparing the pressure-driven performance between the membrane filtration and MD. In this study, several ultrafiltration (UF) and nanofiltration (NF) membranes (NFS, NFX, XT, MT, GC and FILMTEC) were tested for their performance in treating OW (100 ppm). The XT and MT membranes (UF membrane) with contact angles of 70.4 ± 0.2° and 69.6 ± 0.26°, respectively, showed the best performance with high flux and oil removal rate. The two membranes were then tested for long-term performance for two hours with 5000 ppm oil concentration using membrane pressure-filtration and MD. The XT membrane displayed a better oil removal percentage of >99%. MD demonstrated a better removal percentage; the flux reduction was high, with average flux reduction of 82% compared to the membrane pressure-filtration method, which experienced a lower flux reduction of 25%. The hydrophilic MT and XT membranes have the tendency to overcome fouling in both methods. However, for the MD method, wetting occurred due to the feed penetrating the membrane pores, causing flux reduction. Therefore, it is important to identify the performance and characteristics of the prepared membrane, including the best membrane treatment method. To ensure that the MD membrane has good anti-fouling and anti-wetting properties, a simple and reliable membrane surface modification technique is required to be explored. The modified dual layer membrane with hydrophobic/hydrophilic properties is expected to produce effective separation in MD for future study. Full article

(This article belongs to the Special Issue Membrane Science towards Sustainable Development Goals (SDGs))

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11 pages, 3878 KiB

Open AccessArticle

Preparation of a PVA/Chitosan/Glass Fiber Composite Membrane and the Performance in CO₂ Separation

by Yunwu Yu, Chunyang Xie, Yan Wu, Peng Liu, Ye Wan, Xiaowei Sun, Lihua Wang and Yinan Zhang

Membranes 2023, 13(1), 36; https://doi.org/10.3390/membranes13010036 - 28 Dec 2022

Cited by 5 | Viewed by 2038

Abstract

In this study, a novel composite membrane was developed by casting the mixed aqueous solution of chitosan (CS) and polyvinyl alcohol (PVA) on a glass fiber microporous membrane. The polymeric coating of a composite membrane containing amino groups and hydroxyl groups has a [...] Read more.

In this study, a novel composite membrane was developed by casting the mixed aqueous solution of chitosan (CS) and polyvinyl alcohol (PVA) on a glass fiber microporous membrane. The polymeric coating of a composite membrane containing amino groups and hydroxyl groups has a favorable CO₂ affinity and provides an enhanced CO₂ transport mechanism, thereby improving the permeance and selectivity of CO₂. A series of tests for the composite membranes were taken to characterize the chemical structure, morphology, strength, and gas separation properties. ATR-FTIR spectra showed that the chemical structure and functional group of the polymer coating had no obvious change after the heat treatment under 180 °C, while SEM results showed that the composite membranes had a dense surface. The gas permeance and selectivity of the composite membrane were tested using single gases. The results showed that the addition of chitosan can increase the CO₂ permeance which could reach 233 GPU. After a wetting treatment, the CO₂ permeance (454 GPU) and gas selectivity (17.71) were higher than that of dry membranes because moisture promotes the composite membrane transmission. After a heat treatment, the permeance of N₂ decreased more significantly than that of CO₂, which led to an increase in CO₂/N₂ selectivity (10.0). Full article

(This article belongs to the Special Issue Membrane Science towards Sustainable Development Goals (SDGs))

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11 pages, 1559 KiB

Open AccessArticle

The Combined Effects of the Membrane and Flow Channel Development on the Performance and Energy Footprint of Oil/Water Emulsion Filtration

by Nafiu Umar Barambu, Muhammad Roil Bilad, Norazanita Shamsuddin, Shafirah Samsuri, Nik Abdul Hadi Md Nordin and Nasrul Arahman

Membranes 2022, 12(11), 1153; https://doi.org/10.3390/membranes12111153 - 16 Nov 2022

Cited by 1 | Viewed by 1844

Abstract

Membrane filtration is a promising technology for oil/water emulsion filtration due to its excellent removal efficiency of microdroplets of oil in water. However, its performance is highly limited due to the fouling-prone nature of oil droplets on hydrophobic membranes. Membrane filtration typically suffers [...] Read more.

Membrane filtration is a promising technology for oil/water emulsion filtration due to its excellent removal efficiency of microdroplets of oil in water. However, its performance is highly limited due to the fouling-prone nature of oil droplets on hydrophobic membranes. Membrane filtration typically suffers from a low flux and high pumping energy. This study reports a combined approach to tackling the membrane fouling challenge in oil/water emulsion filtration via a membrane and a flow channel development. Two polysulfone (PSF)-based lab-made membranes, namely PSF- PSF-Nonsolvent induced phase separation (NIPS) and PSF-Vapor-induced phase separation (VIPS), were selected, and the flow channel was modified into a wavy path. They were assessed for the filtration of a synthetic oil/water emulsion. The results showed that the combined membrane and flow channel developments enhanced the clean water permeability with a combined increment of 105%, of which 34% was attributed to the increased effective filtration area due to the wavy flow channel. When evaluated for the filtration of an oil/water emulsion, a 355% permeability increment was achieved from 43 for the PSF-NIPS in the straight flow channel to 198 L m⁻² h⁻¹ bar⁻¹ for the PSF-VIPS in the wavy flow channel. This remarkable performance increment was achieved thanks to the antifouling attribute of the developed membrane and enhanced local mixing by the wavy flow channel to limit the membrane fouling. The increase in the filtration performance was translated into up to 78.4% (0.00133 vs. 0.00615 kWh m⁻³) lower in pumping energy. The overall findings demonstrate a significant improvement by adopting multi-pronged approaches in tackling the challenge of membrane fouling for oil/water emulsion filtration, suggesting the potential of this approach to be applied for other feeds. Full article

(This article belongs to the Special Issue Membrane Science towards Sustainable Development Goals (SDGs))

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15 pages, 3249 KiB

Open AccessArticle

Effects of the Structure of Benzenesulfonate-Based Draw Solutes on the Forward Osmosis Process

by DaEun Yang, Yeonsu Cho and Hyo Kang

Membranes 2022, 12(11), 1067; https://doi.org/10.3390/membranes12111067 - 29 Oct 2022

Cited by 4 | Viewed by 2313

Abstract

A series of phosphonium-based ionic liquids (ILs) based on benzenesulfonate derivatives (tetrabutylphosphonium benzenesulfonate ([TBP][BS]), tetrabutylphosphonium 4-methylbenzenesulfonate ([TBP][MBS]), tetrabutylphosphonium 2,4-dimethylbenzenesulfonate ([TBP][DMBS]), and tetrabutylphosphonium 2,4,6-trimethylbenzenesulfonate ([TBP][TMBS])) were synthesized via anion exchange with tetrabutylphosphonium bromide ([TBP][Br]). Then, we characterized the ILs and investigated their suitability as [...] Read more.

A series of phosphonium-based ionic liquids (ILs) based on benzenesulfonate derivatives (tetrabutylphosphonium benzenesulfonate ([TBP][BS]), tetrabutylphosphonium 4-methylbenzenesulfonate ([TBP][MBS]), tetrabutylphosphonium 2,4-dimethylbenzenesulfonate ([TBP][DMBS]), and tetrabutylphosphonium 2,4,6-trimethylbenzenesulfonate ([TBP][TMBS])) were synthesized via anion exchange with tetrabutylphosphonium bromide ([TBP][Br]). Then, we characterized the ILs and investigated their suitability as draw solutes for forward osmosis (FO), focusing on their thermoresponsive properties, conductivities, and osmotic pressures. We found that aqueous [TBP][BS] was not thermoresponsive, but 20 wt% aqueous [TBP][MBS], [TBP][DMBS], and [TBP][TMBS] had lower critical solution temperatures (LCSTs) of approximately 41, 25, and 21 °C, respectively, enabling their easy recovery using waste heat. Based on these findings, 20 wt% aqueous [TBP][DMBS] was tested for its FO performance, and the water and reverse solute fluxes were found to be approximately 9.29 LMH and 1.37 gMH, respectively, in the active layer facing the draw solution (AL-DS) mode and 4.64 LMH and 0.37 gMH, respectively, in the active layer facing the feed solution (AL-FS) mode. Thus, these tetrabutylphosphonium benzenesulfonate-based LCST-type ILs are suitable for drawing solutes for FO process. Full article

(This article belongs to the Special Issue Membrane Science towards Sustainable Development Goals (SDGs))

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25 pages, 6718 KiB

Open AccessArticle

Separation of Soluble Benzene from an Aqueous Solution by Pervaporation Using a Commercial Polydimethylsiloxane Membrane

by Salam H. Rasheed, Salah S. Ibrahim, Qusay F. Alsalhy and Issam K. Salih

Membranes 2022, 12(11), 1040; https://doi.org/10.3390/membranes12111040 - 25 Oct 2022

Cited by 4 | Viewed by 2023

Abstract

A developed polydimethylsiloxane (PDMS) membrane was used to separate soluble benzene compounds (C₆H₆) from an aqueous solution via a pervaporation (PV) process. This membrane was characterized by scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, contact angle (CA), and [...] Read more.

A developed polydimethylsiloxane (PDMS) membrane was used to separate soluble benzene compounds (C₆H₆) from an aqueous solution via a pervaporation (PV) process. This membrane was characterized by scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy, contact angle (CA), and energy-dispersive spectroscopy (EDS). To evaluate the performance of the membrane, the separation factor and permeation flux were estimated in various operating conditions, including the feed temperature, initial benzene concentration, and feed flow rate. The experiments to maximize the separation factor and permeation flux were designed using the response surface method (RSM) that is built into Minitab 18. A quadratic model (nonlinear regression equation) was suggested to obtain mathematical expressions to predict the benzene permeation flux and the separation factor according to the effect of the parameters’ interaction. The optimization of the PV was performed using an RSM that was based on the analysis of variance (ANOVA). The optimal values of the benzene permeation flux and separation factor were 6.7 g/m²·h and 39.8, respectively, at the optimal conditions of temperature (30 °C), initial concentration of benzene (1000 ppm), and feed flow rate (3.5 L/min). It was found that the feed concentration was the most influential parameter, leading to a significant increase in the permeation flux and separation factor of the PDMS membrane. Full article

(This article belongs to the Special Issue Membrane Science towards Sustainable Development Goals (SDGs))

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27 pages, 4321 KiB

Open AccessArticle

Fabrication and Characterisation of MWCNT/Polyvinyl (PVC) Polymer Inclusion Membrane for Zinc (II) Ion Removal from Aqueous Solution

by Nadia Aqilah Khalid, Noor Fazliani Shoparwe, Abdul Hafidz Yusoff, Ahmad Ziad Sulaiman, Abdul Latif Ahmad and Nur Aina Azmi

Membranes 2022, 12(10), 1020; https://doi.org/10.3390/membranes12101020 - 20 Oct 2022

Cited by 3 | Viewed by 2133

Abstract

Heavy metal pollution has prompted researchers to establish the most effective method to tackle the impacts of heavy metals on living things and the environment, which include by applying nanoparticles. An example is the employment of multi-walled carbon nanotubes (MWCNTs) as an additive [...] Read more.

Heavy metal pollution has prompted researchers to establish the most effective method to tackle the impacts of heavy metals on living things and the environment, which include by applying nanoparticles. An example is the employment of multi-walled carbon nanotubes (MWCNTs) as an additive in an intermediate membrane or polymer inclusion membrane (PIM). The MWCNTs were added to enhance the properties and reinforce the transport performance of zinc (II) ion (Zn²⁺) removal from the source phase to the receiver phase by the PIMs. The present study constructed a membrane with a poly(vinyl chloride) (PVC)-based polymer, dioctyl phthalate (DOP) plasticiser, and bis-(2-ethylhexyl) phosphate (B2EHP) carrier incorporated with different concentrations of MWCNTs. The contact angle (CA), water uptake, ion exchange capacity (IEC), and porosity of the fabricated membranes were evaluated. The membrane was also characterised by employing scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and electrochemical impedance spectroscopy (EIS). Subsequently, the fabricated PIM (W1) and mixed matrix (MM)-PIM (W2–W5) samples were assessed under different parameters to acquire the ideal membrane composition and effectiveness. Kinetic modelling of Zn²⁺ removal by the fabricated PIMs under similar conditions was performed to reveal the mechanisms involved. The average removal efficiency of the membranes was >99% at different parameter conditions. Nevertheless, the W3 membrane with 1.0 wt% MWCNT immersed in a 5 mg/L initial Zn²⁺ concentration and 1.0 M receiver solution for seven hours at pH 2 demonstrated the highest percentage of Zn²⁺ removal. The experimental data were best fitted to the pseudo-first-order kinetic model (PFO) in kinetic modelling, and the permeability and flux of the W3 at optimum conditions were 0.053 m s⁻¹ and 0.0532 mol m⁻² s⁻¹, respectively. In conclusion, the transport mechanism of Zn²⁺ was enhanced with the addition of the MWCNTs. Full article

(This article belongs to the Special Issue Membrane Science towards Sustainable Development Goals (SDGs))

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13 pages, 4223 KiB

Open AccessArticle

Effect of Graphene Oxide on the Properties of Polymer Inclusion Membranes for Gold Extraction from Acidic Solution

by Siti Madiha Husna, Abdul Hafidz Yusoff, Mythili Mohan, Nur Aina Azmi, Teo Pao Ter, Noor Fazliani Shoparwe and Ahmad Ziad Sulaiman

Membranes 2022, 12(10), 996; https://doi.org/10.3390/membranes12100996 - 14 Oct 2022

Cited by 3 | Viewed by 2175

Abstract

The cyanidation leaching method is hazardous to the environment, but it is widely applied in the gold mining process because it is effective for gold extraction. This study fabricates polymer inclusion membranes (PIMs), which have environment-friendly properties, with graphene oxide (GO) as an [...] Read more.

The cyanidation leaching method is hazardous to the environment, but it is widely applied in the gold mining process because it is effective for gold extraction. This study fabricates polymer inclusion membranes (PIMs), which have environment-friendly properties, with graphene oxide (GO) as an alternative to the cyanidation leaching method for gold extraction. Poly(vinylidenefluoride-co-hexa-fluoropropylene)-based PIMs with different GO concentrations in five membranes (i.e., M1 (0 wt.%), M2 (0.5 wt.%), M3 (1.0 wt.%), M4 (1.5 wt.%), and M5 (2.0 wt.%)) are studied for their potential to extract gold from a hydrochloric acid solution. The membranes are prepared using di-(2-ethylhexyl) phosphoric acid as the extractant and dioctyl phthalate as the plasticizer. Scanning electron microscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis, ion exchange capacity, and water uptake are used to characterize the physical and chemical properties of the fabricated PIMs. The results show that the optimized membrane for gold extraction is M4 (1.5 wt.% GO), which yields a better performance on thermal stability, ion exchange capacity (IEC), and water uptake. M4 (1.5 wt.% GO) also exhibits a smooth and dense structure, with the maximum extraction efficiency obtained at 84.71% of extracted gold. In conclusion, PIMs can be used as an alternative for extracting gold with a better performance by the presence of 1.5 wt.% GO in membrane composition. Full article

(This article belongs to the Special Issue Membrane Science towards Sustainable Development Goals (SDGs))

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14 pages, 2061 KiB

Open AccessArticle

Nanofiltration of the Remaining Whey after Kefir Grains’ Cultivation

by Marjana Simonič

Membranes 2022, 12(10), 993; https://doi.org/10.3390/membranes12100993 - 13 Oct 2022

Cited by 3 | Viewed by 1452

Abstract

Acid whey is derived from fresh cheese. The proteins were isolated by a monolithic ion-exchange column. The remaining whey fraction was used as a starter culture substrate of kefir grains. The aim of this work was, firstly, to study the possibility of column [...] Read more.

Acid whey is derived from fresh cheese. The proteins were isolated by a monolithic ion-exchange column. The remaining whey fraction was used as a starter culture substrate of kefir grains. The aim of this work was, firstly, to study the possibility of column replacement by a UF membrane. If we succeeded, the concentrate would be used as a starter culture substrate of kefir grains. The second part of the research was to purify the remaining solution. The idea was to separate this solution to the permeate and the concentrate by nanofiltration. Further application of both filtration streams was tested as aqueous solutions or dried matter. Chemical and microbiological analyses were performed of both the permeate and the concentrate. The permeate analyses showed that lactose had been fully removed. The aqueous permeate was not stable, mainly due to an increase of total bacteria from 10³ to 10⁶ CFU/mL. Therefore, the permeate was spray-dried. The dry permeate was added to the moisture solution in different concentrations. The results showed that up to 0.5% of the dry permeate could be added to the moisturizing solution, with negligible changes in properties having the ability to inhibit acne growth. Anaerobic digestion of industrial sludge was performed with the addition of an aqueous concentrate, which showed improvement in anaerobic fermentation. Full article

(This article belongs to the Special Issue Membrane Science towards Sustainable Development Goals (SDGs))

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18 pages, 6133 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Membrane Emulsification—A Novel Solution for Treatment and Reuse of Produced Water from Oil Field

by Aamer Ali, Usman Taqui Syed, Thomas Skovfoged Bak and Cejna Anna Quist-Jensen

Membranes 2022, 12(10), 971; https://doi.org/10.3390/membranes12100971 - 2 Oct 2022

Cited by 5 | Viewed by 3349

Abstract

Produced water (PW) is, by volume, the largest waste product of the oil- and gas-exploration industry and contains pollutants such as hydrocarbons and heavy metals. To meet the stringent environmental regulations, PW must be treated before discharging into the environment. The current study [...] Read more.

Produced water (PW) is, by volume, the largest waste product of the oil- and gas-exploration industry and contains pollutants such as hydrocarbons and heavy metals. To meet the stringent environmental regulations, PW must be treated before discharging into the environment. The current study proposes a novel treatment method where PW is used to prepare oil-in-water emulsion with potential applications within the oil-exploration industry. The emulsions are prepared by applying hollow fiber membrane emulsification (ME) on PW, which inherently contains oil, as to-be-dispersed phase. The results demonstrate that the average droplet size of the emulsions is a function of pressure applied on to-be-dispersed phase and could be customized from 0.24 to 0.65 µm by varying the pressure from 0.25 to 1 bar, respectively. Stability of the emulsions was verified under high pressure and a temperature and storage period of more than 24 h. The calculations showed that an ME unit with <100 kg weight and <1 m³ volume is appropriate to transform the daily average volume of PW from the Danish part of the North Sea into the emulsions. The study provides a novel route, which also complies well with the requirements (low-weight and small spatial footprints) of the offshore oil rigs, to treat and reuse PW within the oil production process and, therefore, eliminates its environmental footprint. Full article

(This article belongs to the Special Issue Membrane Science towards Sustainable Development Goals (SDGs))

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18 pages, 2755 KiB

Open AccessArticle

Xylem-Inspired Hydrous Manganese Dioxide/Aluminum Oxide/Polyethersulfone Mixed Matrix Membrane for Oily Wastewater Treatment

by Teng Sam Yun, Pei Ching Oh, Moau Jian Toh, Yun Kee Yap and Qin Yi Te

Membranes 2022, 12(9), 860; https://doi.org/10.3390/membranes12090860 - 5 Sep 2022

Cited by 1 | Viewed by 1861

Abstract

Ultrafiltration membrane has been widely used for oily wastewater treatment application attributed to its cost-efficiency, ease of operation, and high separation performance. To achieve high membrane flux, the pores of the membrane need to be wetted, which can be attained by using hydrophilic [...] Read more.

Ultrafiltration membrane has been widely used for oily wastewater treatment application attributed to its cost-efficiency, ease of operation, and high separation performance. To achieve high membrane flux, the pores of the membrane need to be wetted, which can be attained by using hydrophilic membrane. Nevertheless, conventional hydrophilic membrane suffered from inhomogeneous dispersion of nanofillers, causing a bottleneck in the membrane flux performance. This called for the need to enhance the dispersion of nanofillers within the polymeric matrix. In this work, in-house-fabricated hydrous manganese dioxide–aluminum oxide (HMO-Al₂O₃) was added into polyethersulfone (PES) dope solution to enhance the membrane flux through a xylem-inspired water transport mechanism on capillary action aided by cohesion force. Binary fillers HMO-Al₂O₃ loading was optimized at 0.5:0.5 in achieving 169 nm membrane mean pore size. Membrane morphology confirmed the formation of macro-void in membrane structure, and this was probably caused by the hydrophilic nanofiller interfacial stress released in PES matrix during the phase inversion process. The superhydrophilic properties of PES 3 in achieving 0° water contact angle was supported by the energy-dispersive X-ray analysis, where it achieved high O element, Mn element, and Al elements of 39.68%, 0.94%, and 5.35%, respectively, indicating that the nanofillers were more homogeneously dispersed in PES matrix. The superhydrophilic property of PES 3 was further supported by high pure water flux at 245.95 L/m².h.bar, which was 3428.70% higher than the pristine PES membrane, 197.1% higher than PES 1 incorporated with HMO nanofiller, and 854.00% higher than PES 5 incorporated with Al₂O₃ nanofillers. Moreover, the excellent membrane separation performance of PES 3 was achieved without compromising the oil rejection capability (98.27% rejection) with 12 g/L (12,000 ppm) oily wastewater. Full article

(This article belongs to the Special Issue Membrane Science towards Sustainable Development Goals (SDGs))

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14 pages, 1831 KiB

Open AccessArticle

Optimization of CO₂/H₂ Separation over Ba-SAPO-34 Zeolite Membrane Synthesized by Microwave Heating

by Tiffany Yit Siew Ng, Vinosha Viriya, Thiam Leng Chew, Yin Fong Yeong, Abdul Latif Ahmad, Chii-Dong Ho and Zeinab Abbas Jawad

Membranes 2022, 12(9), 850; https://doi.org/10.3390/membranes12090850 - 30 Aug 2022

Cited by 4 | Viewed by 1972

Abstract

CO₂/H₂ separation using membrane technology is an important research area in order to obtain high purity hydrogen as one source of clean energy. Finding a suitable inorganic membrane is one of the critical issues, which needs to be explored for [...] Read more.

CO₂/H₂ separation using membrane technology is an important research area in order to obtain high purity hydrogen as one source of clean energy. Finding a suitable inorganic membrane is one of the critical issues, which needs to be explored for CO₂/H₂ separation. In the present study, Ba-SAPO-34 zeolite membrane was synthesized and followed by a modification process. CO₂/H₂ separation of the membrane was investigated by varying the independent process variables (CO₂ % in the feed, pressure difference across the membrane and temperature). Modeling and optimization for the responses (CO₂/H₂ separation selectivity and CO₂ permeance) was performed by applying response surface methodology and central composite design, which is available in Design Expert software. The accuracy of the models in predicting the response was tested by comparing with the experimental value of response and the two values were in good agreement. The optimization of the models gave CO₂ permeance of 19.23 × 10⁻⁷ mol/m² s Pa and CO₂/H₂ separation selectivity of 11.6 at 5% CO₂ in the feed, a pressure difference of 100 kPa, and temperature of 30 °C for Ba-SAPO-34 zeolite membrane. Full article

(This article belongs to the Special Issue Membrane Science towards Sustainable Development Goals (SDGs))

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15 pages, 5049 KiB

Open AccessArticle

Simulation and Experimental Investigation of the Vacuum-Enhanced Direct Membrane Distillation Driven by a Low-Grade Heat Source

by Qingfen Ma, Liang Tong, Chengpeng Wang, Guangfu Cao, Hui Lu, Jingru Li, Xuejin Liu, Xin Feng and Zhongye Wu

Membranes 2022, 12(9), 842; https://doi.org/10.3390/membranes12090842 - 29 Aug 2022

Cited by 3 | Viewed by 1966

Abstract

Vacuum-enhanced direct contact membrane distillation (VEDCMD) has been proven experimentally to improve the permeate flux, compared with direct contact membrane distillation (DCMD). However, the theoretical mechanism for its transmembrane transfer process has not been revealed sufficiently. In this paper, with full consideration of [...] Read more.

Vacuum-enhanced direct contact membrane distillation (VEDCMD) has been proven experimentally to improve the permeate flux, compared with direct contact membrane distillation (DCMD). However, the theoretical mechanism for its transmembrane transfer process has not been revealed sufficiently. In this paper, with full consideration of the different driving forces of diffusion and Poiseuille flow under the vacuum enhancing condition, a theoretical transmembrane model for mass and heat transfer in VEDCMD is proposed. The CFD model and experimental platform are established to verify the theoretical model. The simulated results agree with the experimental data well, and nearly 200% improvement of the permeate flux is obtained when the permeate pressure drops to 30 kPa. The flow fields of the flow along the membrane surface are obtained and analyzed, with good consistency in the variation of the permeate flux. Since all the parameters of the proposed model are independent of the operating condition, the model is much easier for use and has better adaptability to fluctuating operating conditions. Full article

(This article belongs to the Special Issue Membrane Science towards Sustainable Development Goals (SDGs))

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Review

Jump to: Research

30 pages, 3650 KiB

Open AccessReview

An Overview of the Modification Strategies in Developing Antifouling Nanofiltration Membranes

by Nor Naimah Rosyadah Ahmad, Abdul Wahab Mohammad, Ebrahim Mahmoudi, Wei Lun Ang, Choe Peng Leo and Yeit Haan Teow

Membranes 2022, 12(12), 1276; https://doi.org/10.3390/membranes12121276 - 16 Dec 2022

Cited by 35 | Viewed by 3658

Abstract

Freshwater deficiency has become a significant issue affecting many nations’ social and economic development because of the fast-growing demand for water resources. Nanofiltration (NF) is one of the promising technologies for water reclamation application, particularly in desalination, water, and wastewater treatment fields. Nevertheless, [...] Read more.

Freshwater deficiency has become a significant issue affecting many nations’ social and economic development because of the fast-growing demand for water resources. Nanofiltration (NF) is one of the promising technologies for water reclamation application, particularly in desalination, water, and wastewater treatment fields. Nevertheless, membrane fouling remains a significant concern since it can reduce the NF membrane performance and increase operating expenses. Consequently, numerous studies have focused on improving the NF membrane’s resistance to fouling. This review highlights the recent progress in NF modification strategies using three types of antifouling modifiers, i.e., nanoparticles, polymers, and composite polymer/nanoparticles. The correlation between antifouling performance and membrane properties such as hydrophilicity, surface chemistry, surface charge, and morphology are discussed. The challenges and perspectives regarding antifouling modifiers and modification strategies conclude this review. Full article

(This article belongs to the Special Issue Membrane Science towards Sustainable Development Goals (SDGs))

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