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15 pages, 4260 KiB

Open AccessArticle

Evaluation of the Specific Energy Consumption of Sea Water Reverse Osmosis Integrated with Membrane Distillation and Pressure–Retarded Osmosis Processes with Theoretical Models

by Shao-Chi Tsai, Wei-Zhi Huang, Geng-Sheng Lin, Zhen Wang, Kuo-Lun Tung and Ching-Jung Chuang

Membranes 2022, 12(4), 432; https://doi.org/10.3390/membranes12040432 - 16 Apr 2022

Cited by 8 | Viewed by 3462

Abstract

In this study, theoretical models for specific energy consumption (SEC) were established for water recovery in different integrated processes, such as RO-PRO, RO-MD and RO-MD-PRO. Our models can evaluate SEC under different water recovery conditions and for various proportions of supplied waste heat. [...] Read more.

In this study, theoretical models for specific energy consumption (SEC) were established for water recovery in different integrated processes, such as RO-PRO, RO-MD and RO-MD-PRO. Our models can evaluate SEC under different water recovery conditions and for various proportions of supplied waste heat. Simulation results showed that SEC in RO increases with the water recovery rate when the rate is greater than 30%. For the RO-PRO process, the SEC also increases with the water recovery rate when the rate is higher than 38%, but an opposite trend can be observed at lower water recovery rates. If sufficient waste heat is available as the heat source for MD, the integration of MD with the RO or RO-PRO process can significantly reduce SEC. If the total water recovery rate is 50% and MD accounts for 10% of the recovery when sufficient waste heat is available, the SEC values of RO, RO-PRO, RO-MD and RO-MD-PRO are found to be 2.28, 1.47, 1.75 and 0.67 kWh/m³, respectively. These critical analyses provide a road map for the future development of process integration for desalination. Full article

(This article belongs to the Special Issue Special Issue in Honor of Professor Ahmad Fauzi Ismail)

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13 pages, 5537 KiB

Open AccessArticle

Controlling Air Bubble Formation Using Hydrophilic Microfiltration Diffuser for C. vulgaris Cultivation

by Siti Nur Alwani Shafie, Wong Yoong Shen, Jc Jcy Jaymon, Nik Abdul Hadi Md Nordin, Abdelslam Elsir Elsiddig Mohamednour, Muhammad Roil Bilad, Lam Man Kee, Takeshi Matsuura, Mohd Hafiz Dzarfan Othman, Juhana Jaafar and Ahmad Fauzi Ismail

Membranes 2022, 12(4), 414; https://doi.org/10.3390/membranes12040414 - 11 Apr 2022

Cited by 5 | Viewed by 3796

Abstract

In this project, a commercial polytetrafluoroethylene (PTFE) membrane was coated with a thin layer of polyether block amide (PEBAX) via vacuum filtration to improve hydrophilicity and to study the bubble formation. Two parameters, namely PEBAX concentration (of 0–1.5 wt%) and air flow rate [...] Read more.

In this project, a commercial polytetrafluoroethylene (PTFE) membrane was coated with a thin layer of polyether block amide (PEBAX) via vacuum filtration to improve hydrophilicity and to study the bubble formation. Two parameters, namely PEBAX concentration (of 0–1.5 wt%) and air flow rate (of 0.1–50 mL/s), were varied and their effects on the bubble size formation were investigated. The results show that the PEBAX coating reduced the minimum membrane pore size from 0.46 μm without coating (hereafter called PEBAX0) to 0.25 μm for the membrane coated with 1.5wt% of PEBAX (hereafter called PEBAX1.5). The presence of polar functional groups (N-H and C=O) in PEBAX greatly improved the membrane hydrophilicity from 118° for PEBAX0 to 43.66° for PEBAX1.5. At an air flow rate of 43 mL/s, the equivalent bubble diameter size decreased from 2.71 ± 0.14 cm for PEBAX0 to 1.51 ± 0.02 cm for PEBAX1.5. At the same air flow rate, the frequency of bubble formation increased six times while the effective gas–liquid contact area increased from 47.96 cm²/s to 85.6 cm²/s. The improved growth of C. vulgaris from 0.6 g/L to 1.3 g/L for PEBAX1.5 also shows the potential of the PEBAX surface coating porous membrane as an air sparger. Full article

(This article belongs to the Special Issue Special Issue in Honor of Professor Ahmad Fauzi Ismail)

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13 pages, 6629 KiB

Open AccessArticle

Effects of Benzalkonium Chloride Contents on Structures, Properties, and Ultrafiltration Performances of Chitosan-Based Nanocomposite Membranes

by Fitri Khoerunnisa, Mita Nurhayati, Noor Azmi Aulia Annisa, Siti Fatimah, Nisa Nashrah, Hendrawan Hendrawan, Young-Gun Ko, Eng-Poh Ng and Pakorn Opaprakasit

Membranes 2022, 12(3), 268; https://doi.org/10.3390/membranes12030268 - 25 Feb 2022

Cited by 5 | Viewed by 3186

Abstract

The effects of benzalkonium chloride (BKC) contents on the structure, properties, and ultrafiltration performance of chitosan-based nanocomposite membranes containing poly(ethylene glycol) and multi-walled carbon nanotube (chitosan/BKC/PEG/CNT) were examined. The membranes were prepared by a mixing solution method and phase inversion before being characterized [...] Read more.

The effects of benzalkonium chloride (BKC) contents on the structure, properties, and ultrafiltration performance of chitosan-based nanocomposite membranes containing poly(ethylene glycol) and multi-walled carbon nanotube (chitosan/BKC/PEG/CNT) were examined. The membranes were prepared by a mixing solution method and phase inversion before being characterized with microscopic techniques, tensile tests, thermogravimetric analysis, water contact angle, and porosity measurements. The performance of the nanocomposite membranes in regard to permeability (flux) and permselectivity (rejection) was examined. The results show that the incorporation of BKC produced nanocomposite membranes with smaller pore structures and improved physico-chemical properties, such as an increase in porosity and surface roughness (R_a = 45.15 to 145.35 nm and R_q = 53.69 to 167.44 nm), an enhancement in the elongation at break from 45 to 109%, and an enhancement in the mechanical strength from 31.2 to 45.8 MPa. In contrast, a decrease in the membrane hydrophilicity (water contact angle increased from 56.3 to 82.8°) and a decrease in the average substructure pore size from 32.64 to 10.08 nm were observed. The membrane rejection performances toward Bovine Serum Albumin (BSA) increased with the BKC composition in both dead-end and cross-flow filtration processes. The chitosan/BKC/PEG/CNT nanocomposite membranes have great potential in wastewater treatments for minimizing biofouling without reducing the water purification performance. Full article

(This article belongs to the Special Issue Special Issue in Honor of Professor Ahmad Fauzi Ismail)

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22 pages, 10125 KiB

Open AccessArticle

Bisphenol A Removal Using Visible Light Driven Cu₂O/PVDF Photocatalytic Dual Layer Hollow Fiber Membrane

by Siti Hawa Mohamed Noor, Mohd Hafiz Dzarfan Othman, Watsa Khongnakorn, Oulavanh Sinsamphanh, Huda Abdullah, Mohd Hafiz Puteh, Tonni Agustiono Kurniawan, Hazirah Syahirah Zakria, Tijjani El-badawy, Ahmad Fauzi Ismail, Mukhlis A. Rahman and Juhana Jaafar

Membranes 2022, 12(2), 208; https://doi.org/10.3390/membranes12020208 - 10 Feb 2022

Cited by 20 | Viewed by 2800

Abstract

Bisphenol A (BPA) is amongst the endocrine disrupting compounds (EDCs) that cause illness to humans and in this work was removed using copper (I) oxide (Cu₂O) visible light photocatalyst which has a narrow bandgap of 2.2 eV. This was done by [...] Read more.

Bisphenol A (BPA) is amongst the endocrine disrupting compounds (EDCs) that cause illness to humans and in this work was removed using copper (I) oxide (Cu₂O) visible light photocatalyst which has a narrow bandgap of 2.2 eV. This was done by embedding Cu₂O into polyvinylidene fluoride (PVDF) membranes to generate a Cu₂O/PVDF dual layer hollow fiber (DLHF) membrane using a co-extrusion technique. The initial ratio of 0.25 Cu₂O/PVDF was used to study variation of the outer dope extrusion flowrate for 3 mL/min, 6 mL/min and 9 mL/min. Subsequently, the best flowrate was used to vary Cu₂O/PVDF for 0.25, 0.50 and 0.75 with fixed outer dope extrusion flowrate. Under visible light irradiation, 10 mg/L of BPA was used to assess the membranes performance. The results show that the outer and inner layers of the membrane have finger-like structures, whereas the intermediate section of the membrane has a sponge-like structure. With high porosity up to 63.13%, the membrane is hydrophilic and exhibited high flux up to 13,891 L/m²h. The optimum photocatalytic membrane configuration is 0.50 Cu₂O/PVDF DLHF membrane with 6 mL/min outer dope flowrate, which was able to remove 75% of 10 ppm BPA under visible light irradiation without copper leaching into the water sample. Full article

(This article belongs to the Special Issue Special Issue in Honor of Professor Ahmad Fauzi Ismail)

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21 pages, 5991 KiB

Open AccessArticle

Poly(lactic acid)-poly(ethylene glycol)/Magnesium Silicate Membrane for Methylene Blue Removal: Adsorption Behavior, Mechanism, Ionic Strength and Reusability Studies

by Norilyani Izzati Hasanuddin, Wan Nur Aini Wan Mokhtar, Rizafizah Othaman and Farah Hannan Anuar

Membranes 2022, 12(2), 198; https://doi.org/10.3390/membranes12020198 - 9 Feb 2022

Cited by 6 | Viewed by 2332

Abstract

In this work, the effect of magnesium silicate (MgSiO₃) as a filler on poly(lactic acid)-poly(ethylene glycol) (PLA-PEG) membrane was investigated towards the enhancement of adsorption capacity for removal of cationic dye. The preparation and fabrication of membranes were performed through copolymerization [...] Read more.

In this work, the effect of magnesium silicate (MgSiO₃) as a filler on poly(lactic acid)-poly(ethylene glycol) (PLA-PEG) membrane was investigated towards the enhancement of adsorption capacity for removal of cationic dye. The preparation and fabrication of membranes were performed through copolymerization and phase inversion techniques. Analysis of functional groups, tensile strength, morphology and surface wettability were employed in the characterization of the membranes. After the addition of MgSiO₃, it was found that the PLA-PEG/MgSiO₃ membrane presented a higher hydrophilic property with improved mechanical strength. Next, the adsorption of methylene blue (MB) was optimized using response surface methodology (RSM) with the parameters mass of membrane and initial concentration of MB solution. The effects of pH and ionic strength were also examined to determine the mechanism involved during adsorption processes, which later were found to be electrostatic interaction and ion-exchange mechanism. From the isotherms and kinetics studies, the PLA-PEG/MgSiO₃ membrane was well fitted by the Freundlich model and pseudo second order model, respectively. This membrane also demonstrated reusable character of up to six cycles. Full article

(This article belongs to the Special Issue Special Issue in Honor of Professor Ahmad Fauzi Ismail)

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20 pages, 5083 KiB

Open AccessArticle

Critical Flux and Fouling Analysis of PVDF-Mixed Matrix Membranes for Reclamation of Refinery-Produced Wastewater: Effect of Mixed Liquor Suspended Solids Concentration and Aeration

by Erna Yuliwati, Ahmad Fauzi Ismail, Mohd Hafiz Dzarfan Othman and Mohammad Mahdi A. Shirazi

Membranes 2022, 12(2), 161; https://doi.org/10.3390/membranes12020161 - 28 Jan 2022

Cited by 10 | Viewed by 3656

Abstract

Fouling tends to cause a significant increase in hydraulic resistance, decreased permeate flux, or increased transmembrane pressure (TMP) when a process is operated under constant TMP or constant flux conditions. To control membrane fouling and maintain sustainable operation, the concept of [...] Read more.

Fouling tends to cause a significant increase in hydraulic resistance, decreased permeate flux, or increased transmembrane pressure (TMP) when a process is operated under constant TMP or constant flux conditions. To control membrane fouling and maintain sustainable operation, the concept of critical flux has been discussed by several researchers. Various fouling mechanisms, such as macromolecule adsorption, pore plugging, or cake build-up, as well as hydrodynamic conditions, for example aeration, can take place at the membrane surface. This study aimed to investigate the effects of mixed liquor suspended solid (MLSS) concentration and air bubble flow rate (ABFR) on the critical flux and fouling behavior, when treating refinery-produced wastewater. To determine the critical flux values, the experimental flux-steps were the following: (1) the filtration began with a 30 min step duration at a low flux (10 to 20 L/m²h); (2) at the end of this step (after 30 min), the permeate flux was increased, (3) this step was repeated until the TMP did not remain constant at the constant permeate flux, (4) the critical flux was then achieved. A critical flux model with an R² of 0.9 was, therefore, derived, which indicates that the particle properties were regulated by the suspended solids. The increase of MLSS concentration, from 3 mg/L to 4.5 mg/L, resulted in a decrease of the permeate flux by 18%. Moreover, an increase in ABFR, from 1.2 mL/min to 2.4 mL/min, increased the permeate flux, but this decreased with a greater flow rate of aeration. To assess the stability and reversibility of fouling during critical flux (J_c) determination using a mixed matrix membrane, flux-step methods were utilized. A step height of 14.3 L/m²h and 30 min duration were arbitrarily chosen. The flux increased to 32.5 L/m²h with a slight increase of trans membrane pressure (TMP), while the rate of increase became significant at a higher flux of 143.6 L/m²h, due to fouling. Overall, this study proved that the response of MLSS concentration and aeration affected the membrane performance, based on the critical flux and fouling behavior. Full article

(This article belongs to the Special Issue Special Issue in Honor of Professor Ahmad Fauzi Ismail)

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21 pages, 6568 KiB

Open AccessEditor’s ChoiceArticle

Distillate Flux Enhancement of Direct Contact Membrane Distillation Modules with Inserting Cross-Diagonal Carbon-Fiber Spacers

by Chii-Dong Ho, Luke Chen, Jun-Wei Lim, Po-Hung Lin and Pin-Tsen Lu

Membranes 2021, 11(12), 973; https://doi.org/10.3390/membranes11120973 - 9 Dec 2021

Cited by 5 | Viewed by 2714

Abstract

A new design of direct-contact membrane distillation (DCMD) modules with cross-diagonal carbon-fiber spacers of various hydrodynamic angles in flow channels to promote turbulence intensity was proposed to enhance pure water productivity. Attempts to reduce the temperature polarization coefficient were achieved by inserting cross-diagonal [...] Read more.

A new design of direct-contact membrane distillation (DCMD) modules with cross-diagonal carbon-fiber spacers of various hydrodynamic angles in flow channels to promote turbulence intensity was proposed to enhance pure water productivity. Attempts to reduce the temperature polarization coefficient were achieved by inserting cross-diagonal carbon-fiber spacers in channels, which create wakes and eddies in both heat and mass transfer behaviors to enhance the permeate flux enhancement. A simplified equation was formulated to obtain the theoretical predictions of heat transfer coefficients in the current DCMD device. The permeate fluxes and temperature distributions of both hot and cold feed streams are represented graphically with the inlet volumetric flow rate and inlet temperature of the hot saline feed stream as parameters. The higher distillate flux of countercurrent-flow operations for saline water desalination was accomplished as compared to the concurrent-flow operations of various hydrodynamic angles. The results show that the agreement between the theoretical predictions and experimental results is reasonably good. The effects of countercurrent-flow operations and inserting carbon fiber spacers have confirmed technical feasibility and device performance enhancement of up to 45%. The influences of operating and design parameters on the pure water productivity with the expense of energy consumption are also discussed. Full article

(This article belongs to the Special Issue Special Issue in Honor of Professor Ahmad Fauzi Ismail)

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20 pages, 5130 KiB

Open AccessArticle

Optimization of a High-Performance Poly(diallyl dimethylammonium chloride)-alumina-perfluorooctanoate Intercalated Ultrafiltration Membrane for Treating Emulsified Oily Wastewater via Response Surface Methodology Approach

by Yusuf Olabode Raji, Mohd Hafiz Dzarfan Othman, Nik Abdul Hadi Sapiaa Md Nordin, Mohd Ridhwan Adam, Khairul Anwar Mohamad Said, Kabir Abogunde Abdulyekeen, Ahmad Fauzi Ismail, Mukhlis A. Rahman, Juhana Jaafar and Suriani Abu Bakar

Membranes 2021, 11(12), 956; https://doi.org/10.3390/membranes11120956 - 1 Dec 2021

Cited by 8 | Viewed by 2854

Abstract

This research aimed to investigate the ultrafiltration of water from emulsified oily wastewater through the application of surface-functionalized ceramic membrane to enhance its water permeability based on optimized parameters using a cross-flow filtration system. The interactive effects of feed concentration (10–1000 ppm), pH [...] Read more.

This research aimed to investigate the ultrafiltration of water from emulsified oily wastewater through the application of surface-functionalized ceramic membrane to enhance its water permeability based on optimized parameters using a cross-flow filtration system. The interactive effects of feed concentration (10–1000 ppm), pH (4–10), and pressure (0–3 bar) on the water flux and oil rejection were investigated. Central composite design (CCD) from response surface methodology (RSM) was employed for statistical analysis, modeling, and optimization of operating conditions. The analysis of variance (ANOVA) results showed that the oil rejection and water flux models were significant with p-values of 0.0001 and 0.0075, respectively. In addition, good correlation coefficients of 0.997 and 0.863 were obtained for the oil rejection and water flux models, respectively. The optimum conditions for pressure, pH, and feed concentration were found to be 1.5 bar, pH 8.97, and 10 ppm, respectively with water flux and oil rejection maintained at 152 L/m²·h and 98.72%, respectively. Hence, the functionalized ultrafiltration ceramic membrane enables the separation efficiency of the emulsified oil in water to be achieved. Full article

(This article belongs to the Special Issue Special Issue in Honor of Professor Ahmad Fauzi Ismail)

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10 pages, 3743 KiB

Open AccessEditor’s ChoiceArticle

Development of Pure Silica CHA Membranes for CO₂ Separation

by Gabriel Gama da Silva Figueiredo, Daishi Takayama, Katsunori Ishii, Mikihiro Nomura, Takamasa Onoki, Takuya Okuno, Hiromasa Tawarayama and Shinji Ishikawa

Membranes 2021, 11(12), 926; https://doi.org/10.3390/membranes11120926 - 25 Nov 2021

Cited by 7 | Viewed by 3251

Abstract

Thin pure-silica chabazite (Si-CHA) membranes have been synthesized by using a secondary growth method on a porous silica substrate. A CO₂ permeance of 2.62 × 10⁻⁶ mol m⁻² s⁻¹ Pa⁻¹ with a CO₂/CH₄ permeance ratio [...] Read more.

Thin pure-silica chabazite (Si-CHA) membranes have been synthesized by using a secondary growth method on a porous silica substrate. A CO₂ permeance of 2.62 × 10⁻⁶ mol m⁻² s⁻¹ Pa⁻¹ with a CO₂/CH₄ permeance ratio of 62 was obtained through a Si-CHA membrane crystallized for 8 h using a parent gel of H₂O/SiO₂ ratio of 4.6. The CO₂ permeance through the Si-CHA membrane on a porous silica substrate was twice as high as that through the membrane synthesized on a porous alumina substrate, which displayed a similar zeolite layer thickness. Full article

(This article belongs to the Special Issue Special Issue in Honor of Professor Ahmad Fauzi Ismail)

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13 pages, 2263 KiB

Open AccessArticle

Highly Permeable Mixed Matrix Hollow Fiber Membrane as a Latent Route for Hydrogen Purification from Hydrocarbons/Carbon Dioxide

by Yu-Ting Lin, Ming-Yen Wey and Hui-Hsin Tseng

Membranes 2021, 11(11), 865; https://doi.org/10.3390/membranes11110865 - 10 Nov 2021

Cited by 6 | Viewed by 2485

Abstract

This work reported on the fabrication and investigation of a mixed matrix hollow fiber membrane (MMHFM) by incorporating commercially available alumina particles into a polyetherimide (PEI) polymer matrix. These MMHFMs were prepared by the dry-wet spinning technique. Accordingly, optimizing the spinning parameters, including [...] Read more.

This work reported on the fabrication and investigation of a mixed matrix hollow fiber membrane (MMHFM) by incorporating commercially available alumina particles into a polyetherimide (PEI) polymer matrix. These MMHFMs were prepared by the dry-wet spinning technique. Accordingly, optimizing the spinning parameters, including the air gap distance and flow rate ratio, is key to determining the gas separation performance. However, there are few studies regarding the effect of the filler dimensions. Consequently, three sizes of alumina particles, 20 nm, 30 nm, and 1000 nm, were respectively added into the PEI phase to examine the influence of filler size on gas permeation property. Moreover, the permeation properties of lower hydrocarbons (i.e., ethane and propane) were also measured to evaluate potential for emerging applications. The results indicated the as-synthesized membrane exhibited a remarkable hydrogen permeance of 1065.24 GPU, and relatively high separation factors of 4.53, 5.77, and 5.39 for H₂/CO₂, H₂/C₂H₆, and H₂/C₃H₈, respectively. This resulted from good compatibility between the larger fillers and the PEI polymer, as well as a reduction in the finger-like voids. Overall, the MMHFM in this work was deemed to be a promising candidate to separate hydrogen from gas streams, based on the comparison of the separation performance against other reported studies. Full article

(This article belongs to the Special Issue Special Issue in Honor of Professor Ahmad Fauzi Ismail)

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14 pages, 23227 KiB

Open AccessArticle

Effect of Gravity and Various Operating Conditions on Proton Exchange Membrane Water Electrolysis Cell Performance

by Yena Choi, Woojung Lee and Youngseung Na

Membranes 2021, 11(11), 822; https://doi.org/10.3390/membranes11110822 - 27 Oct 2021

Cited by 22 | Viewed by 4187

Abstract

Water electrolysis is an eco-friendly method for the utilization of renewable energy sources which provide intermittent power supply. Proton exchange membrane water electrolysis (PEMWE) has a high efficiency in this regard. However, the two-phase flow of water and oxygen at the anode side [...] Read more.

Water electrolysis is an eco-friendly method for the utilization of renewable energy sources which provide intermittent power supply. Proton exchange membrane water electrolysis (PEMWE) has a high efficiency in this regard. However, the two-phase flow of water and oxygen at the anode side causes performance degradation, and various operating conditions affect the performance of PEMWE. In this study, the effects of four control parameters (operating temperature, flow rate, cell orientation, and pattern of the channel) on the performance of PEMWE were investigated. The effects of the operating conditions on its performance were examined using a 25 cm² single-cell. Evaluation tests were conducted using in situ methods such as polarization curves and electrochemical impedance spectroscopy. The results demonstrated that a high operating temperature and low flow rate reduce the activation and ohmic losses, and thereby enhance the performance of PEMWE. Additionally, the cell orientation affects the performance of PEMWE owing to the variation in the two-phase flow regime. It was observed that the slope of specific sections in the polarization curve rapidly increases at a specific cell voltage. Full article

(This article belongs to the Special Issue Special Issue in Honor of Professor Ahmad Fauzi Ismail)

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20 pages, 3867 KiB

Open AccessArticle

Effects of an Alternating Magnetic Field towards Dispersion of α-Fe₂O₃/TiO₂ Magnetic Filler in PPO_dm Polymer for CO₂/CH₄ Gas Separation

by Yun Kee Yap and Pei Ching Oh

Membranes 2021, 11(8), 641; https://doi.org/10.3390/membranes11080641 - 20 Aug 2021

Cited by 5 | Viewed by 3025

Abstract

Magnetic-field-induced dispersion of magnetic fillers has been proven to improve the gas separation performance of mixed matrix membranes (MMMs). However, the magnetic field induced is usually in a horizontal or vertical direction. Limited study has been conducted on the effects of alternating magnetic [...] Read more.

Magnetic-field-induced dispersion of magnetic fillers has been proven to improve the gas separation performance of mixed matrix membranes (MMMs). However, the magnetic field induced is usually in a horizontal or vertical direction. Limited study has been conducted on the effects of alternating magnetic field (AMF) direction towards the dispersion of particles. Thus, this work focuses on the incorporation and dispersion of ferromagnetic iron oxide–titanium (IV) dioxide (αFe₂O₃/TiO₂) particles in a poly (2,6-dimethyl-1,4-phenylene) oxide (PPO_dm) membrane via an AMF to investigate its effect on the magnetic filler dispersion and correlation towards gas separation performance. The fillers were incorporated into PPO_dm polymer via a spin-coating method at a 1, 3, and 5 wt% filler loading. The MMM with the 3 wt% loading showed the best performance in terms of particle dispersion and gas separation performance. The three MMMs were refabricated in an alternating magnetic field, and the MMM with the 3 wt% loading presented the best performance. The results display an increment in selectivity by 100% and a decrement in CO₂ permeability by 97% to an unmagnetized MMM for the 3 wt% loading. The degree of filler dispersion was quantified and measured using Area Disorder of Delaunay Triangulation mapped onto the filler on binarized MMM images. The results indicate that the magnetized MMM presents a greater degree of dispersion than the unmagnetized MMM. Full article

(This article belongs to the Special Issue Special Issue in Honor of Professor Ahmad Fauzi Ismail)

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17 pages, 27463 KiB

Open AccessArticle

Modified Zeolite/Polysulfone Mixed Matrix Membrane for Enhanced CO₂/CH₄ Separation

by Lanisha Devi Anbealagan, Tiffany Yit Siew Ng, Thiam Leng Chew, Yin Fong Yeong, Siew Chun Low, Yit Thai Ong, Chii-Dong Ho and Zeinab Abbas Jawad

Membranes 2021, 11(8), 630; https://doi.org/10.3390/membranes11080630 - 16 Aug 2021

Cited by 15 | Viewed by 4322

Abstract

In recent years, mixed matrix membranes (MMMs) have received worldwide attention for their potential to offer superior gas permeation and separation performance involving CO₂ and CH₄. However, fabricating defect-free MMMs still remains as a challenge where the incorporation of fillers [...] Read more.

In recent years, mixed matrix membranes (MMMs) have received worldwide attention for their potential to offer superior gas permeation and separation performance involving CO₂ and CH₄. However, fabricating defect-free MMMs still remains as a challenge where the incorporation of fillers into MMMs has usually led to some issues including formation of undesirable interfacial voids, which may jeopardize the gas separation performance of the MMMs. This current work investigated the incorporation of zeolite RHO and silane-modified zeolite RHO (NH₂–RHO) into polysulfone (PSf) based MMMs with the primary aim of enhancing the membrane’s gas permeation and separation performance. The synthesized zeolite RHO, NH₂–RHO, and fabricated membranes were characterized by X-ray diffraction (XRD) analysis, Fourier transform infrared-attenuated total reflection (FTIR-ATR), thermogravimetric analysis (TGA) and field emission scanning election microscopy (FESEM). The effects of zeolite loading in the MMMs on the CO₂/CH₄ separation performance were investigated. By incorporating 1 wt% of zeolite RHO into the MMMs, the CO₂ permeability and ideal CO₂/CH₄ selectivity slightly increased by 4.2% and 2.7%, respectively, compared to that of a pristine PSf membrane. On the other hand, a significant enhancement of 45% in ideal CO₂/CH₄ selectivity was attained by MMMs incorporated with 2 wt% of zeolite NH₂-RHO compared to a pristine PSf membrane. Besides, all MMMs incorporated with zeolite NH₂-RHO displayed higher ideal CO₂/CH₄ selectivity than that of the MMMs incorporated with zeolite RHO. By incorporating 1–3 wt% zeolite NH₂-RHO into PSf matrix, MMMs without interfacial voids were successfully fabricated. Consequently, significant enhancement in ideal CO₂/CH₄ selectivity was enabled by the incorporation of zeolite NH₂–RHO into MMMs. Full article

(This article belongs to the Special Issue Special Issue in Honor of Professor Ahmad Fauzi Ismail)

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24 pages, 10143 KiB

Open AccessArticle

Research and Development Journey and Future Trends of Hollow Fiber Membranes for Purification Applications (1970–2020): A Bibliometric Analysis

by Muhammad Ayub, Mohd Hafiz Dzarfan Othman, Siti Hamimah Sheikh Abdul Kadir, Adnan Ali, Imran Ullah Khan, Mohd Zamri Mohd Yusop, Takeshi Matsuura, Ahmad Fauzi Ismail, Mukhlis A. Rahman and Juhana Jaafar

Membranes 2021, 11(8), 600; https://doi.org/10.3390/membranes11080600 - 7 Aug 2021

Cited by 8 | Viewed by 4193

Abstract

Hollow fiber membrane (HFM) technology has received significant attention due to its broad range separation and purification applications in the industry. In the current study, we applied bibliometric analysis to evaluate the global research trends on key applications of HFMs by evaluating the [...] Read more.

Hollow fiber membrane (HFM) technology has received significant attention due to its broad range separation and purification applications in the industry. In the current study, we applied bibliometric analysis to evaluate the global research trends on key applications of HFMs by evaluating the global publication outputs. Results obtained from 5626 published articles (1970–2020) from the Scopus database were further manipulated using VOSviewer software through cartography analysis. The study emphasizes the performance of most influential annual publications covering mainstream journals, leading countries, institutions, leading authors and author’s keywords, as well as future research trends. The study found that 62% of the global HFM publications were contributed by China, USA, Singapore, Japan and Malaysia, followed by 77 other countries. This study will stimulate the researchers by showing the future-minded research directions when they select new research areas, particularly in those related to water treatment, biomedical and gas separation applications of HFM. Full article

(This article belongs to the Special Issue Special Issue in Honor of Professor Ahmad Fauzi Ismail)

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12 pages, 2793 KiB

Open AccessArticle

Phosphate Adsorption from Aqueous Solution Using Electrospun Cellulose Acetate Nanofiber Membrane Modified with Graphene Oxide/Sodium Dodecyl Sulphate

by Nur Ain Atiqah Mohd Amin, Mohd Akmali Mokhter, Nurrulhidayah Salamun and Wan M. Asyraf Wan Mahmood

Membranes 2021, 11(7), 546; https://doi.org/10.3390/membranes11070546 - 20 Jul 2021

Cited by 13 | Viewed by 3328

Abstract

Eutrophication and water pollution caused by a high concentration of phosphate are two concerning issues that affect water quality worldwide. A novel cellulose-based adsorbent, cellulose acetate/graphene oxide/sodium dodecyl sulphate (CA/GO/SDS), was developed for water treatment. A 13% CA solution in a mixture of [...] Read more.

Eutrophication and water pollution caused by a high concentration of phosphate are two concerning issues that affect water quality worldwide. A novel cellulose-based adsorbent, cellulose acetate/graphene oxide/sodium dodecyl sulphate (CA/GO/SDS), was developed for water treatment. A 13% CA solution in a mixture of acetone:dimethylacetamide (2:1) has been electrospun and complexed with a GO/SDS solution. The field emission scanning electron microscope (FESEM) showed that the CA membrane was pure white, while the CA/GO/SDS membrane was not as white as CA and its colour became darker as the GO content increased. The process of phosphate removal from the solutions was found to be aided by the hydroxyl groups on the surface of the CA modified with GO/SDS, as shown by infrared spectroscopy. An optimization condition for the adsorption process was studied by varying pH, immersion time, and the mass of the membrane. The experimental results from phosphate adsorption showed that CA/GO/SDS had an excellent pH adaptability, with an optimum pH of 7, and maximum removal (>87.0%) was observed with a membrane mass of 0.05 g at an initial concentration of 25 mg L⁻¹. A kinetic study revealed that 180 min of contact time could adsorb about 87.2% of phosphate onto the CA/GO/SDS membrane. A typical pseudo-second-order kinetic model successfully portrayed the kinetic sorption of phosphate, and the adsorption equilibrium data were well-correlated with the Langmuir adsorption model, suggesting the monolayer coverage of adsorbed molecules. Full article

(This article belongs to the Special Issue Special Issue in Honor of Professor Ahmad Fauzi Ismail)

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Review

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30 pages, 3531 KiB

Open AccessReview

Progress and Prospects of Nanocellulose-Based Membranes for Desalination and Water Treatment

by Asif Saud, Haleema Saleem and Syed Javaid Zaidi

Membranes 2022, 12(5), 462; https://doi.org/10.3390/membranes12050462 - 25 Apr 2022

Cited by 28 | Viewed by 5132

Abstract

Membrane-based desalination has proved to be the best solution for solving the water shortage issues globally. Membranes are extremely beneficial in the effective recovery of clean water from contaminated water sources, however, the durability as well as the separation efficiency of the membranes [...] Read more.

Membrane-based desalination has proved to be the best solution for solving the water shortage issues globally. Membranes are extremely beneficial in the effective recovery of clean water from contaminated water sources, however, the durability as well as the separation efficiency of the membranes are restricted by the type of membrane materials/additives used in the preparation processes. Nanocellulose is one of the most promising green materials for nanocomposite preparation due to its biodegradability, renewability, abundance, easy modification, and exceptional mechanical properties. This nanocellulose has been used in membrane development for desalination application in the recent past. The study discusses the application of membranes based on different nanocellulose forms such as cellulose nanocrystals, cellulose nanofibrils, and bacterial nanocellulose for water desalination applications such as nanofiltration, reverse osmosis, pervaporation, forward osmosis, and membrane distillation. From the analysis of studies, it was confirmed that the nanocellulose-based membranes are effective in the desalination application. The chemical modification of nanocellulose can definitely improve the surface affinity as well as the reactivity of membranes for the efficient separation of specific contaminants/ions. Full article

(This article belongs to the Special Issue Special Issue in Honor of Professor Ahmad Fauzi Ismail)

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37 pages, 4714 KiB

Open AccessReview

A Review on the Use of Membrane Technology Systems in Developing Countries

by Nur Hidayati Othman, Nur Hashimah Alias, Nurul Syazana Fuzil, Fauziah Marpani, Munawar Zaman Shahruddin, Chun Ming Chew, Kam Meng David Ng, Woei Jye Lau and Ahmad Fauzi Ismail

Membranes 2022, 12(1), 30; https://doi.org/10.3390/membranes12010030 - 27 Dec 2021

Cited by 80 | Viewed by 15282

Abstract

Fulfilling the demand of clean potable water to the general public has long been a challenging task in most developing countries due to various reasons. Large-scale membrane water treatment systems have proven to be successful in many advanced countries in the past two [...] Read more.

Fulfilling the demand of clean potable water to the general public has long been a challenging task in most developing countries due to various reasons. Large-scale membrane water treatment systems have proven to be successful in many advanced countries in the past two decades. This paves the way for developing countries to study the feasibility and adopt the utilization of membrane technology in water treatment. There are still many challenges to overcome, particularly on the much higher capital and operational cost of membrane technology compared to the conventional water treatment system. This review aims to delve into the progress of membrane technology for water treatment systems, particularly in developing countries. It first concentrates on membrane classification and its application in water treatment, including membrane technology progress for large-scale water treatment systems. Then, the fouling issue and ways to mitigate the fouling will be discussed. The feasibility of membrane technologies in developing countries was then evaluated, followed by a discussion on the challenges and opportunities of the membrane technology implementation. Finally, the current trend of membrane research was highlighted to address future perspectives of the membrane technologies for clean water production. Full article

(This article belongs to the Special Issue Special Issue in Honor of Professor Ahmad Fauzi Ismail)

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28 pages, 2642 KiB

Open AccessEditor’s ChoiceReview

A Review on the Design and Performance of Enzyme-Aided Catalysis of Carbon Dioxide in Membrane, Electrochemical Cell and Photocatalytic Reactors

by Fatin Nasreen Ahmad Rizal Lim, Fauziah Marpani, Victoria Eliz Anak Dilol, Syazana Mohamad Pauzi, Nur Hidayati Othman, Nur Hashimah Alias, Nik Raikhan Nik Him, Jianquan Luo and Norazah Abd Rahman

Membranes 2022, 12(1), 28; https://doi.org/10.3390/membranes12010028 - 27 Dec 2021

Cited by 7 | Viewed by 4267

Abstract

Multi-enzyme cascade catalysis involved three types of dehydrogenase enzymes, namely, formate dehydrogenase (FDH), formaldehyde dehydrogenase (FaldDH), alcohol dehydrogenase (ADH), and an equimolar electron donor, nicotinamide adenine dinucleotide (NADH), assisting the reaction is an interesting pathway to reduce thermodynamically stable molecules of CO₂ [...] Read more.

Multi-enzyme cascade catalysis involved three types of dehydrogenase enzymes, namely, formate dehydrogenase (FDH), formaldehyde dehydrogenase (FaldDH), alcohol dehydrogenase (ADH), and an equimolar electron donor, nicotinamide adenine dinucleotide (NADH), assisting the reaction is an interesting pathway to reduce thermodynamically stable molecules of CO₂ from the atmosphere. The biocatalytic sequence is interesting because it operates under mild reaction conditions (low temperature and pressure) and all the enzymes are highly selective, which allows the reaction to produce three basic chemicals (formic acid, formaldehyde, and methanol) in just one pot. There are various challenges, however, in applying the enzymatic conversion of CO₂, namely, to obtain high productivity, increase reusability of the enzymes and cofactors, and to design a simple, facile, and efficient reactor setup that will sustain the multi-enzymatic cascade catalysis. This review reports on enzyme-aided reactor systems that support the reduction of CO₂ to methanol. Such systems include enzyme membrane reactors, electrochemical cells, and photocatalytic reactor systems. Existing reactor setups are described, product yields and biocatalytic productivities are evaluated, and effective enzyme immobilization methods are discussed. Full article

(This article belongs to the Special Issue Special Issue in Honor of Professor Ahmad Fauzi Ismail)

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19 pages, 1187 KiB

Open AccessReview

Recent Mitigation Strategies on Membrane Fouling for Oily Wastewater Treatment

by Nur Fatihah Zulkefli, Nur Hashimah Alias, Nur Shafiqah Jamaluddin, Norfadhilatuladha Abdullah, Shareena Fairuz Abdul Manaf, Nur Hidayati Othman, Fauziah Marpani, Muhammad Shafiq Mat-Shayuti and Tutuk Djoko Kusworo

Membranes 2022, 12(1), 26; https://doi.org/10.3390/membranes12010026 - 25 Dec 2021

Cited by 38 | Viewed by 5971

Abstract

The discharge of massive amounts of oily wastewater has become one of the major concerns among the scientific community. Membrane filtration has been one of the most used methods of treating oily wastewater due to its stability, convenience handling, and durability. However, the [...] Read more.

The discharge of massive amounts of oily wastewater has become one of the major concerns among the scientific community. Membrane filtration has been one of the most used methods of treating oily wastewater due to its stability, convenience handling, and durability. However, the continuous occurrence of membrane fouling aggravates the membrane’s performance efficiency. Membrane fouling can be defined as the accumulation of various materials in the pores or surface of the membrane that affect the permeate’s quantity and quality. Many aspects of fouling have been reviewed, but recent methods for fouling reduction in oily wastewater have not been explored and discussed sufficiently. This review highlights the mitigation strategies to reduce membrane fouling from oily wastewater. We first review the membrane technology principle for oily wastewater treatment, followed by a discussion on different fouling mechanisms of inorganic fouling, organic fouling, biological fouling, and colloidal fouling for better understanding and prevention of membrane fouling. Recent mitigation strategies to reduce fouling caused by oily wastewater treatment are also discussed. Full article

(This article belongs to the Special Issue Special Issue in Honor of Professor Ahmad Fauzi Ismail)

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15 pages, 9111 KiB

Open AccessReview

Recent Progress and Challenges in Hollow Fiber Membranes for Wastewater Treatment and Resource Recovery

by Rosmawati Naim, Goh Pei Sean, Zinnirah Nasir, Nadzirah Mohd Mokhtar and Nor Amirah Safiah Muhammad

Membranes 2021, 11(11), 839; https://doi.org/10.3390/membranes11110839 - 29 Oct 2021

Cited by 17 | Viewed by 3891

Abstract

Membrane processes have been extensively employed in diverse applications, specifically in industrial wastewater treatment. The technological development in membrane processes has rapidly advanced and accelerated beyond its common principle and operation. Tremendous efforts have been made in the advancement of membrane materials, fabrication [...] Read more.

Membrane processes have been extensively employed in diverse applications, specifically in industrial wastewater treatment. The technological development in membrane processes has rapidly advanced and accelerated beyond its common principle and operation. Tremendous efforts have been made in the advancement of membrane materials, fabrication method, membrane modification and integration with other technologies that can augment the existing membrane processes to another level. This review presents the recent development of hollow fiber membranes applied in wastewater treatment and resource recovery. The membrane working principles and treatment mechanism were discussed thoroughly, with the recent development of these hollow fiber membranes highlighted based on several types of membrane application. The current challenges and limitations which may hinder this technology from expanding were critically described to offer a better perspective for this technology to be adopted in various potential applications. Full article

(This article belongs to the Special Issue Special Issue in Honor of Professor Ahmad Fauzi Ismail)

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40 pages, 7657 KiB

Open AccessReview

Surface Design of Liquid Separation Membrane through Graft Polymerization: A State of the Art Review

by Deepa Suresh, Pei Sean Goh, Ahmad Fauzi Ismail and Nidal Hilal

Membranes 2021, 11(11), 832; https://doi.org/10.3390/membranes11110832 - 28 Oct 2021

Cited by 44 | Viewed by 11795

Abstract

Surface modification of membranes is an effective approach for imparting unique characteristics and additional functionalities to the membranes. Chemical grafting is a commonly used membrane modification technique due to its versatility in tailoring and optimizing the membrane surface with desired functionalities. Various types [...] Read more.

Surface modification of membranes is an effective approach for imparting unique characteristics and additional functionalities to the membranes. Chemical grafting is a commonly used membrane modification technique due to its versatility in tailoring and optimizing the membrane surface with desired functionalities. Various types of polymers can be precisely grafted onto the membrane surface and the operating conditions of grafting can be tailored to further fine-tune the membrane surface properties. This review focuses on the recent strategies in improving the surface design of liquid separation membranes through grafting-from technique, also known as graft polymerization, to improve membrane performance in wastewater treatment and desalination applications. An overview on membrane technology processes such as pressure-driven and osmotically driven membrane processes are first briefly presented. Grafting-from surface chemical modification approaches including chemical initiated, plasma initiated and UV initiated approaches are discussed in terms of their features, advantages and limitations. The innovations in membrane surface modification techniques based on grafting-from techniques are comprehensively reviewed followed by some highlights on the current challenges in this field. It is concluded that grafting-from is a versatile and effective technique to introduce various functional groups to enhance the surface properties and separation performances of liquid separation membranes. Full article

(This article belongs to the Special Issue Special Issue in Honor of Professor Ahmad Fauzi Ismail)

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31 pages, 6024 KiB

Open AccessReview

Waste Reutilization in Polymeric Membrane Fabrication: A New Direction in Membranes for Separation

by Pei Sean Goh, Mohd Hafiz Dzarfan Othman and Takeshi Matsuura

Membranes 2021, 11(10), 782; https://doi.org/10.3390/membranes11100782 - 12 Oct 2021

Cited by 30 | Viewed by 6806

Abstract

In parallel to the rapid growth in economic and social activities, there has been an undesirable increase in environmental degradation due to the massively produced and disposed waste. The need to manage waste in a more innovative manner has become an urgent matter. [...] Read more.

In parallel to the rapid growth in economic and social activities, there has been an undesirable increase in environmental degradation due to the massively produced and disposed waste. The need to manage waste in a more innovative manner has become an urgent matter. In response to the call for circular economy, some solid wastes can offer plenty of opportunities to be reutilized as raw materials for the fabrication of functional, high-value products. In the context of solid waste-derived polymeric membrane development, this strategy can pave a way to reduce the consumption of conventional feedstock for the production of synthetic polymers and simultaneously to dampen the negative environmental impacts resulting from the improper management of these solid wastes. The review aims to offer a platform for overviewing the potentials of reutilizing solid waste in liquid separation membrane fabrication by covering the important aspects, including waste pretreatment and raw material extraction, membrane fabrication and characterizations, as well as the separation performance evaluation of the resultant membranes. Three major types of waste-derived polymeric raw materials, namely keratin, cellulose, and plastics, are discussed based on the waste origins, limitations in the waste processing, and their conversion into polymeric membranes. With the promising material properties and viability of processing facilities, recycling and reutilization of waste resources for membrane fabrication are deemed to be a promising strategy that can bring about huge benefits in multiple ways, especially to make a step closer to sustainable and green membrane production. Full article

(This article belongs to the Special Issue Special Issue in Honor of Professor Ahmad Fauzi Ismail)

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