Membranes

18 pages, 7141 KiB

Open AccessArticle

Novel Module-Based Membrane Reactor Design Approach for Improved Operability Performance

by Brent A. Bishop and Fernando V. Lima

Membranes 2021, 11(2), 157; https://doi.org/10.3390/membranes11020157 - 23 Feb 2021

Cited by 6 | Viewed by 3137

This work aims to address the design and control challenges caused by the integration of phenomena and the loss of degrees of freedom (DOF) that occur in the intensification of membrane reactor units. First, a novel approach to designing membrane reactor units is [...] Read more.

This work aims to address the design and control challenges caused by the integration of phenomena and the loss of degrees of freedom (DOF) that occur in the intensification of membrane reactor units. First, a novel approach to designing membrane reactor units is proposed. This approach consists of designing smaller modules based on specific phenomena such as heat exchange, reactions, and mass transport and combining them in series to produce the final modular membrane-based unit. This approach to designing membrane reactors is then assessed using a process operability analysis for the first time to maximize the operability index, as a way of quantifying the operational performance of intensified processes. This work demonstrates that by designing membrane reactors in this way, the operability of the original membrane reactor design can be significantly improved, translating to an improvement in achievability for a potential control structure implementation. Full article

(This article belongs to the Special Issue Membrane Reactors for Process Intensification: Recent Advances and Key Applications)

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9 pages, 876 KiB

Open AccessPerspective

Recent Developments in High-Performance Membranes for CO₂ Separation

by Zi Tong and Ali K. Sekizkardes

Membranes 2021, 11(2), 156; https://doi.org/10.3390/membranes11020156 - 23 Feb 2021

Cited by 23 | Viewed by 5581

Abstract

In this perspective article, we provide a detailed outlook on recent developments of high-performance membranes used in CO₂ separation applications. A wide range of membrane materials including polymers of intrinsic microporosity, thermally rearranged polymers, metal–organic framework membranes, poly ionic liquid membranes, and [...] Read more.

In this perspective article, we provide a detailed outlook on recent developments of high-performance membranes used in CO₂ separation applications. A wide range of membrane materials including polymers of intrinsic microporosity, thermally rearranged polymers, metal–organic framework membranes, poly ionic liquid membranes, and facilitated transport membranes were surveyed from the recent literature. In addition, mixed matrix and polymer blend membranes were covered. The CO₂ separation performance, as well as other membrane properties such as film flexibility, processibility, aging, and plasticization, were analyzed. Full article

(This article belongs to the Special Issue Advanced Membranes for Carbon Capture)

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17 pages, 1498 KiB

Open AccessEditor’s ChoiceReview

Membrane Protein Stabilization Strategies for Structural and Functional Studies

by Ekaitz Errasti-Murugarren, Paola Bartoccioni and Manuel Palacín

Membranes 2021, 11(2), 155; https://doi.org/10.3390/membranes11020155 - 22 Feb 2021

Cited by 20 | Viewed by 6131

Abstract

Accounting for nearly two-thirds of known druggable targets, membrane proteins are highly relevant for cell physiology and pharmacology. In this regard, the structural determination of pharmacologically relevant targets would facilitate the intelligent design of new drugs. The structural biology of membrane proteins is [...] Read more.

Accounting for nearly two-thirds of known druggable targets, membrane proteins are highly relevant for cell physiology and pharmacology. In this regard, the structural determination of pharmacologically relevant targets would facilitate the intelligent design of new drugs. The structural biology of membrane proteins is a field experiencing significant growth as a result of the development of new strategies for structure determination. However, membrane protein preparation for structural studies continues to be a limiting step in many cases due to the inherent instability of these molecules in non-native membrane environments. This review describes the approaches that have been developed to improve membrane protein stability. Membrane protein mutagenesis, detergent selection, lipid membrane mimics, antibodies, and ligands are described in this review as approaches to facilitate the production of purified and stable membrane proteins of interest for structural and functional studies. Full article

(This article belongs to the Special Issue Experimental and Computational Methods for Membrane Protein Design)

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23 pages, 5221 KiB

Open AccessArticle

A Unified, One Fluid Model for the Drag of Fluid and Solid Dispersals by Permeate Flux towards a Membrane Surface

by Amgad Salama, Shuyu Sun and Tao Zhang

Membranes 2021, 11(2), 154; https://doi.org/10.3390/membranes11020154 - 22 Feb 2021

Cited by 1 | Viewed by 2169

Abstract

The drag of dispersals towards a membrane surface is a consequence of the filtration process. It also represents the first step towards the development of the problem of fouling. In order to combat membrane fouling, it is important to understand such drag mechanisms [...] Read more.

The drag of dispersals towards a membrane surface is a consequence of the filtration process. It also represents the first step towards the development of the problem of fouling. In order to combat membrane fouling, it is important to understand such drag mechanisms and provide a modeling framework. In this work, a new modeling and numerical approach is introduced that is based on a one-domain model in which both the dispersals and the surrounding fluid are dealt with as a fluid with heterogeneous property fields. Furthermore, because of the fact that the geometry of the object assumes axial symmetry and the configuration remains fixed, the location of the interface may be calculated using geometrical relationships. This alleviates the need to define an indicator function and solve a hyperbolic equation to update the configuration. Furthermore, this approach simplifies the calculations and significantly reduces the computational burden required otherwise if one incorporates a hyperbolic equation to track the interface. To simplify the calculations, we consider the motion of an extended cylindrical object. This allows a reduction in the dimensions of the problem to two, thereby reducing the computational burden without a loss of generality. Furthermore, for this particular case there exists an approximate analytical solution that accounts for the effects of the confining boundaries that usually exist in real systems. We use such a setup to provide the benchmarking of the different averaging techniques for the calculations of properties at the cell faces and center, particularly in the cells involving the interface. Full article

(This article belongs to the Special Issue Flow and Transport in Membranes: Modeling and Experimental Verification)

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20 pages, 6435 KiB

Open AccessArticle

Insights into the Influence of Membrane Permeability and Structure on Osmotically-Driven Membrane Processes

by Jing Wei, Qianhong She and Xin Liu

Membranes 2021, 11(2), 153; https://doi.org/10.3390/membranes11020153 - 22 Feb 2021

Cited by 13 | Viewed by 3344

Abstract

The success of osmotically-driven membrane (OM) technology relies critically on high-performance membranes. Yet trade-off of membrane properties, often further complicated by the strongly non-linear dependence of OM performance on them, imposes important constraint on membrane performance. This work systematically characterized four typical commercial [...] Read more.

The success of osmotically-driven membrane (OM) technology relies critically on high-performance membranes. Yet trade-off of membrane properties, often further complicated by the strongly non-linear dependence of OM performance on them, imposes important constraint on membrane performance. This work systematically characterized four typical commercial osmotic membranes in terms of intrinsic separation parameters, structure and surface properties. The osmotic separation performance and membrane scaling behavior of these membranes were evaluated to elucidate the interrelationship of these properties. Experimental results revealed that membranes with smaller structural parameter (S) and higher water/solute selectivity underwent lower internal concentration polarization (ICP) and exhibited higher forward osmosis (FO) efficiency (i.e., higher ratio of experimental water flux over theoretical water flux). Under the condition with low ICP, membrane water permeability (A) had dominant effect on water flux. In this case, the investigated thin film composite membrane (TFC, A = 2.56 L/(m² h bar), S = 1.14 mm) achieved a water flux up to 82% higher than that of the asymmetric cellulose triacetate membrane (CTA-W(P), A = 1.06 L/(m² h bar), S = 0.73 mm). In contrast, water flux became less dependent on the A value but was affected more by membrane structure under the condition with severe ICP, and the membrane exhibited lower FO efficiency. The ratio of water flux (J_{v TFC}/J_{v CTA-W(P)}) decreased to 0.55 when 0.5 M NaCl feed solution and 2 M NaCl draw solution were used. A framework was proposed to evaluate the governing factors under different conditions and to provide insights into the membrane optimization for targeted OM applications. Full article

(This article belongs to the Special Issue Membrane-based Technologies for Water and Energy Sustainability)

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14 pages, 2748 KiB

Open AccessArticle

Recovery of Acid and Base from Sodium Sulfate Containing Lithium Carbonate Using Bipolar Membrane Electrodialysis

by Wenjie Gao, Qinxiang Fang, Haiyang Yan, Xinlai Wei and Ke Wu

Membranes 2021, 11(2), 152; https://doi.org/10.3390/membranes11020152 - 22 Feb 2021

Cited by 27 | Viewed by 6005

Abstract

Lithium carbonate is an important chemical raw material that is widely used in many contexts. The preparation of lithium carbonate by acid roasting is limited due to the large amounts of low-value sodium sulfate waste salts that result. In this research, bipolar membrane [...] Read more.

Lithium carbonate is an important chemical raw material that is widely used in many contexts. The preparation of lithium carbonate by acid roasting is limited due to the large amounts of low-value sodium sulfate waste salts that result. In this research, bipolar membrane electrodialysis (BMED) technology was developed to treat waste sodium sulfate containing lithium carbonate for conversion of low-value sodium sulfate into high-value sulfuric acid and sodium hydroxide. Both can be used as raw materials in upstream processes. In order to verify the feasibility of the method, the effects of the feed salt concentration, current density, flow rate, and volume ratio on the desalination performance were determined. The conversion rate of sodium sulfate was close to 100%. The energy consumption obtained under the best experimental conditions was 1.4 kWh·kg⁻¹. The purity of the obtained sulfuric acid and sodium hydroxide products reached 98.32% and 98.23%, respectively. Calculated under the best process conditions, the total process cost of BMED was estimated to be USD 0.705 kg⁻¹ Na₂SO₄, which is considered low and provides an indication of the potential economic and environmental benefits of using applying this technology. Full article

(This article belongs to the Special Issue Ion-Exchange Membranes and Processes (Volume II))

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25 pages, 5230 KiB

Open AccessArticle

Improvement of Barrier Properties of Biodegradable Polybutylene Succinate/Graphene Nanoplatelets Nanocomposites Prepared by Melt Process

by Raphaël Cosquer, Sébastien Pruvost and Fabrice Gouanvé

Membranes 2021, 11(2), 151; https://doi.org/10.3390/membranes11020151 - 22 Feb 2021

Cited by 25 | Viewed by 3616

Abstract

Polybutylene Succinate (PBS)/Graphene nanoplatelets (GnP) nanocomposites over a range of GnP from 0 to 1.35 wt.%. were prepared by a melt process. A mixture of individual graphene nanosheets and aggregates was obtained by the addition of GnP in the PBS matrix. The presence [...] Read more.

Polybutylene Succinate (PBS)/Graphene nanoplatelets (GnP) nanocomposites over a range of GnP from 0 to 1.35 wt.%. were prepared by a melt process. A mixture of individual graphene nanosheets and aggregates was obtained by the addition of GnP in the PBS matrix. The presence of these fillers did not significantly modify the morphology, crystalline microstructure of the matrix or its thermal stability. However, a slight reinforcement effect of PBS was reported in the presence of GnP. The water sorption isotherm modelling with Guggenheim, Andersen and De Boer (GAB) equation and Zimm-Lundberg theory allowed a phenomenological analysis at the molecular scale. The presence of GnP did not modify the water sorption capacity of the PBS matrix. From a kinetic point of view, a decrease of the diffusion coefficient with the increasing GnP content was obtained and was attributed to a tortuosity effect. The influence of water activity was discussed over a range of 0.5 to 1 and 0 to 0.9 for water and dioxygen permeability. Improvement of the barrier properties by 38% and 35% for water and dioxygen permeability respectively were obtained. Full article

(This article belongs to the Special Issue Advances on Bio-Based Materials for Food Packaging Applications)

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13 pages, 2511 KiB

Open AccessReview

Recent Impact of Microfluidics on Skin Models for Perspiration Simulation

by Genís Rabost-Garcia, Josep Farré-Lladós and Jasmina Casals-Terré

Membranes 2021, 11(2), 150; https://doi.org/10.3390/membranes11020150 - 21 Feb 2021

Cited by 11 | Viewed by 3894

Abstract

Skin models offer an in vitro alternative to human trials without their high costs, variability, and ethical issues. Perspiration models, in particular, have gained relevance lately due to the rise of sweat analysis and wearable technology. The predominant approach to replicate the key [...] Read more.

Skin models offer an in vitro alternative to human trials without their high costs, variability, and ethical issues. Perspiration models, in particular, have gained relevance lately due to the rise of sweat analysis and wearable technology. The predominant approach to replicate the key features of perspiration (sweat gland dimensions, sweat rates, and skin surface characteristics) is to use laser-machined membranes. Although they work effectively, they present some limitations at the time of replicating sweat gland dimensions. Alternative strategies in terms of fabrication and materials have also showed similar challenges. Additional research is necessary to implement a standardized, simple, and accurate model representing sweating for wearable sensors testing. Full article

(This article belongs to the Special Issue Microfluidics and MEMS Technology for Membranes)

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5 pages, 220 KiB

Open AccessEditorial

Electromembrane Processes: Experiments and Modelling

by Luigi Gurreri, Alessandro Tamburini and Giorgio Micale

Membranes 2021, 11(2), 149; https://doi.org/10.3390/membranes11020149 - 20 Feb 2021

Cited by 3 | Viewed by 1969

Abstract

This Special Issue of Membranes journal focuses on electromembrane processes and is motivated by the increasing interest of the scientific community towards their characterization by experiments and modelling for several applications [...] Full article

(This article belongs to the Special Issue Electromembrane Processes: Experiments and Modelling)

15 pages, 10236 KiB

Open AccessArticle

A Molecular Model of PEMFC Catalyst Layer: Simulation on Reactant Transport and Thermal Conduction

by Wenkai Wang, Zhiguo Qu, Xueliang Wang and Jianfei Zhang

Membranes 2021, 11(2), 148; https://doi.org/10.3390/membranes11020148 - 20 Feb 2021

Cited by 28 | Viewed by 4420

Abstract

Minimizing platinum (Pt) loading while reserving high reaction efficiency in the catalyst layer (CL) has been confirmed as one of the key issues in improving the performance and application of proton exchange membrane fuel cells (PEMFCs). To enhance the reaction efficiency of Pt [...] Read more.

Minimizing platinum (Pt) loading while reserving high reaction efficiency in the catalyst layer (CL) has been confirmed as one of the key issues in improving the performance and application of proton exchange membrane fuel cells (PEMFCs). To enhance the reaction efficiency of Pt catalyst in CL, the interfacial interactions in the three-phase interface, i.e., carbon, Pt, and ionomer should be first clarified. In this study, a molecular model containing carbon, Pt, and ionomer compositions is built and the radial distribution functions (RDFs), diffusion coefficient, water cluster morphology, and thermal conductivity are investigated after the equilibrium molecular dynamics (MD) and nonequilibrium MD simulations. The results indicate that increasing water content improves water aggregation and cluster interconnection, both of which benefit the transport of oxygen and proton in the CL. The growing amount of ionomer promotes proton transport but generates additional resistance to oxygen. Both the increase of water and ionomer improve the thermal conductivity of the C. The above-mentioned findings are expected to help design catalyst layers with optimized Pt content and enhanced reaction efficiency, and further improve the performance of PEMFCs. Full article

(This article belongs to the Special Issue Development of Novel Materials for Proton Exchange Membrane Fuel Cells)

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13 pages, 2496 KiB

Open AccessArticle

Efficient Fluoride Removal from Aqueous Solution Using Zirconium-Based Composite Nanofiber Membranes

by Alaa Mohamed, Elvia P. Valadez Sanchez, Evgenia Bogdanova, Britta Bergfeldt, Ammar Mahmood, Roman V. Ostvald and Tawheed Hashem

Membranes 2021, 11(2), 147; https://doi.org/10.3390/membranes11020147 - 20 Feb 2021

Cited by 20 | Viewed by 3593

Abstract

Herein, composite nanofiber membranes (CNMs) derived from UiO-66 and UiO-66-NH₂ Zr-metal-organic frameworks (MOFs) were successfully prepared, and they exhibited high performance in adsorptive fluoride removal from aqueous media. The resultant CNMs were confirmed using different techniques, such as X-ray diffraction (XRD), field [...] Read more.

Herein, composite nanofiber membranes (CNMs) derived from UiO-66 and UiO-66-NH₂ Zr-metal-organic frameworks (MOFs) were successfully prepared, and they exhibited high performance in adsorptive fluoride removal from aqueous media. The resultant CNMs were confirmed using different techniques, such as X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and Brunauer–Emmett–Teller (BET) in addition to Fourier-transform infrared spectroscopy (FTIR). The parameters that govern the fluoride adsorption were evaluated, including adsorbent dose, contact time, and pH value, in addition to initial concentration. The crystalline structures of CNMs exhibited high hydrothermal stability and remained intact after fluoride adsorption. It could also be observed that the adsorbent dose has a significant effect on fluoride removal at high alkaline values. The results show that UiO-66-NH₂ CNM exhibited high fluoride removal due to electrostatic interactions that strongly existed between F⁻ and metal sites in MOF in addition to hydrogen bonds formed with MOF amino groups. The fluoride removal efficiency reached 95% under optimal conditions of 20 mg L⁻¹, pH of 8, and 40% adsorbent dose at 60 min. The results revealed that UiO-66-NH₂ CNM possesses a high maximum adsorption capacity (95 mg L⁻¹) over UiO-66 CNM (75 mg L⁻¹), which exhibited better fitting with the pseudo-second-order model. Moreover, when the initial fluoride concentration increased from 20 to 100 mg/L, fluoride adsorption decreased by 57% (UiO-66 CNM) and 30% (UiO-66-NH₂ CNM) after 60 min. After three cycles, CNM revealed the regeneration ability, demonstrating that UiO-66-NH₂ CNMs are auspicious adsorbents for fluoride from an aqueous medium. Full article

(This article belongs to the Section Membrane Applications)

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20 pages, 9252 KiB

Open AccessArticle

Optimization of Fuel Cell Performance Using Computational Fluid Dynamics

by Tabbi Wilberforce, Oluwatosin Ijaodola, Ogungbemi Emmanuel, James Thompson, Abdul Ghani Olabi, Mohammad Ali Abdelkareem, Enas Taha Sayed, Khaled Elsaid and Hussein M. Maghrabie

Membranes 2021, 11(2), 146; https://doi.org/10.3390/membranes11020146 - 20 Feb 2021

Cited by 19 | Viewed by 5300

Abstract

A low cost bipolar plate materials with a high fuel cell performance is important for the establishment of Proton Exchange Membrane (PEM ) fuel cells into the competitive world market. In this research, the effect of different bipolar plates material such as Aluminum [...] Read more.

A low cost bipolar plate materials with a high fuel cell performance is important for the establishment of Proton Exchange Membrane (PEM ) fuel cells into the competitive world market. In this research, the effect of different bipolar plates material such as Aluminum (Al), Copper (Cu), and Stainless Steel (SS) of a single stack of proton exchange membrane (PEM) fuel cells was investigated both numerically and experimentally. Firstly, a three dimensional (3D) PEM fuel cell model was developed, and simulations were conducted using commercial computational fluid dynamics (CFD) ANSYS FLUENT to examine the effect of each bipolar plate materials on cell performance. Along with cell performance, significant parameters distributions like temperature, pressure, a mass fraction of hydrogen, oxygen, and water is presented. Then, an experimental study of a single cell of Al, Cu, and SS bipolar plate material was used in the verification of the numerical investigation. Finally, polarization curves of numerical and experimental results was compared for validation, and the result shows that Al serpentine bipolar plate material performed better than Cu and SS materials. The outcome of the investigation was in tandem to the fact that due to adsorption on metal surfaces, hydrogen molecules is more stable on Al surface than Cu and SS surfaces. Full article

(This article belongs to the Special Issue Development of Novel Materials for Proton Exchange Membrane Fuel Cells)

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19 pages, 2292 KiB

Open AccessArticle

Layer-by-Layer Coating of MK-40 Heterogeneous Membrane with Polyelectrolytes Creates Samples with Low Electrical Resistance and Weak Generation of H⁺ and OH⁻ Ions

by Kseniia Tsygurina, Olesya Rybalkina, Konstantin Sabbatovskiy, Evgeniy Kirichenko, Vladimir Sobolev and Ksenia Kirichenko

Membranes 2021, 11(2), 145; https://doi.org/10.3390/membranes11020145 - 20 Feb 2021

Cited by 8 | Viewed by 2057

Abstract

Ion exchange membranes covered with layers of polyelectrolytes of alternating charges are characterized by very high monovalent selectivity. This allows the use of such membranes for electrodialytic fractionation of multicomponent solutions. However, the very existence of the boundary at which differently charged layers [...] Read more.

Ion exchange membranes covered with layers of polyelectrolytes of alternating charges are characterized by very high monovalent selectivity. This allows the use of such membranes for electrodialytic fractionation of multicomponent solutions. However, the very existence of the boundary at which differently charged layers come in contact can hinder a membrane’s effectiveness by limiting its ion permeability, raising levels of H⁺ and OH⁻ ions (thus shifting the pH) and increasing the electrical resistance of the membrane, which leads to increased energy consumption. To test how these properties would be changed, we created cheap layer-by-layer-modified membranes based on the heterogeneous MK-40 membrane, on which we adsorbed layers of polyallylamine and sulfonated polystyrene. We created samples with 3, 4, and 5 layers of polyelectrolytes and characterized them. We showed that the application of layers did not decrease the efficiency of the membrane, since the electrical resistance of the modified samples, which increased after application of the first oppositely charged layer, declined with the application of the following layers and became comparable to that of the substrate, while their limiting current density was higher and the shift of pH of treated solution was low in magnitude and comparable with that of the substrate membrane. Full article

(This article belongs to the Section Membrane Applications)

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3 pages, 198 KiB

Open AccessEditorial

Membrane Distillation Process

by Alessandra Criscuoli

Membranes 2021, 11(2), 144; https://doi.org/10.3390/membranes11020144 - 18 Feb 2021

Cited by 9 | Viewed by 2456

Abstract

The water stress that we have been experiencing in the last few years is driving the development of new technologies for the purification and recovery of water [...] Full article

(This article belongs to the Special Issue Membrane Distillation Process)

15 pages, 2587 KiB

Open AccessArticle

Highly Dispersed CeO_x Hybrid Nanoparticles for Perfluorinated Sulfonic Acid Ionomer–Poly(tetrafluoethylene) Reinforced Membranes with Improved Service Life

by Juhee Ahn, Mobina Irshad Ali, Jun Hyun Lim, Yejun Park, In Kee Park, Denis Duchesne, Lisa Chen, Juyoung Kim and Chang Hyun Lee

Membranes 2021, 11(2), 143; https://doi.org/10.3390/membranes11020143 - 18 Feb 2021

Cited by 10 | Viewed by 2987

Abstract

CeO_x hybrid nanoparticles were synthesized and evaluated for use as radical scavengers, in place of commercially available Ce(NO₃)₃ and CeO₂ nanoparticles, to avoid deterioration of the initial electrochemical performance and/or spontaneous aggregation/precipitation issues encountered in polymer electrolyte membranes. [...] Read more.

CeO_x hybrid nanoparticles were synthesized and evaluated for use as radical scavengers, in place of commercially available Ce(NO₃)₃ and CeO₂ nanoparticles, to avoid deterioration of the initial electrochemical performance and/or spontaneous aggregation/precipitation issues encountered in polymer electrolyte membranes. When CeO_x hybrid nanoparticles were used for membrane formation, the resulting membranes exhibited improved proton conductivity (improvement level = 2–15% at 30–90 °C), and thereby electrochemical single cell performance, because the –OH groups on the hybrid nanoparticles acted as proton conductors. In spite of a small amount (i.e., 1.7 mg/cm³) of introduction, their antioxidant effect was sufficient enough to alleviate the radical-induced decomposition of perfluorinated sulfonic acid ionomer under a Fenton test condition and to extend the chemical durability of the resulting reinforced membranes under fuel cell operating conditions. Full article

(This article belongs to the Special Issue Polymer Electrolyte Membranes)

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15 pages, 4342 KiB

Open AccessArticle

The Permeability and Selectivity of the Polyamide Reverse Osmosis Membrane were Significantly Enhanced by PhSiCl₃

by Junjie Yu, Kaifeng Gu, Binbin Yang, Kaizhen Wang, Yong Zhou and Congjie Gao

Membranes 2021, 11(2), 142; https://doi.org/10.3390/membranes11020142 - 18 Feb 2021

Cited by 3 | Viewed by 2526

Abstract

The work briefly introduces the nano-composite reverse osmosis (RO) membrane with more permeability and selective performance, and we adopted the phenyltrichlorosilane precursor with better chemical stability and greater spatial resistance. The phenyltrichlorosilane concentration was mainly discussed in this work. The in-situ hydrolysis of [...] Read more.

The work briefly introduces the nano-composite reverse osmosis (RO) membrane with more permeability and selective performance, and we adopted the phenyltrichlorosilane precursor with better chemical stability and greater spatial resistance. The phenyltrichlorosilane concentration was mainly discussed in this work. The in-situ hydrolysis of phenyltrichlorosilane and the occurrence of ammonia hydrolysis make it effectively incorporated into the polyamide film. The covalent bond and hydrogen bond of phenyltrichlorosilane and polyamide (PA) can be realized. The phenyl group can extend in the polyamide polymer network and give the film corresponding functions. There will be fewer non-selective defects between phenyltrichlorosilane and PA. Under the premise of maintaining the water-salt selectivity of the membrane, along with the increase of benzene trichlorosilane loading, the 300% pure water flux can be achieved and the desalination rate remains at 98.1–98.9%. This reverse osmosis (RO) is suitable for household water purification. Full article

(This article belongs to the Section Polymeric Membranes)

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13 pages, 4305 KiB

Open AccessArticle

Reliable Sea Water Ro Operation with High Water Recovery and No-Chlorine/No-Sbs Dosing in Arabian Gulf, Saudi Arabia

by Hiroki Miyakawa, Mohammed Maghram Al Shaiae, Troy N. Green, Yohito Ito, Yuichi Sugawara, Makoto Onishi, Yoshinari Fusaoka, Mohammed Farooque Ayumantakath and Ahmed Saleh Al Amoudi

Membranes 2021, 11(2), 141; https://doi.org/10.3390/membranes11020141 - 17 Feb 2021

Cited by 11 | Viewed by 3724

Abstract

For providing advanced desalination the combination of the improvement of water recovery ratio in the reverse osmosis (RO) process and the No-Chlorine/No-Sodium Bisulfite (SBS) Dosing process was studied. In order to prevent membrane fouling even in high recovery water operations, an advanced two-stage [...] Read more.

For providing advanced desalination the combination of the improvement of water recovery ratio in the reverse osmosis (RO) process and the No-Chlorine/No-Sodium Bisulfite (SBS) Dosing process was studied. In order to prevent membrane fouling even in high recovery water operations, an advanced two-stage design was implemented to (1) control the permeate flux through the RO membrane module, (2) optimize the system to reduce contaminant build-up and (3) eliminate the use of chlorine and SBS, which can accelerate membrane fouling. The system was evaluated by monitoring the biofouling and the microorganisms proliferation on the membrane surface based on membrane biofilm formation rate (mBFR). The pilot plant was operated in the condition of a water recovery rate of 55%. As a result, the system was operated for longer than four months without membrane cleaning (clean in place; CIP) and the possibility of operation for seven months without CIP was confirmed by the extrapolation of the pressure values. In addition, the mBFR is a reliable tool for water quality assessment, based on a comparison between the fouling tendency estimated from the mBFR and the actual membrane surface condition from autopsy study and the effectiveness No-Chlorine/No-SBS Dosing process was verified from mBFR of pretreated seawater. Full article

(This article belongs to the Special Issue Seawater Reverse Osmosis Desalination)

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10 pages, 1952 KiB

Open AccessArticle

Effect of Nano Silicon Dioxide Coating Films on the Quality Characteristics of Fresh-Cut Cantaloupe

by Rokayya Sami, Manal Almatrafi, Abeer Elhakem, Mona Alharbi, Nada Benajiba and Mahmoud Helal

Membranes 2021, 11(2), 140; https://doi.org/10.3390/membranes11020140 - 17 Feb 2021

Cited by 19 | Viewed by 2736

Abstract

The prime objective of the research was to explore the coating effects of chitosan and nano-silicon dioxide with nisin as an antimicrobial agent on physicochemical properties, microbiological stability, and sensorial quality changes during the storage at 4 °C. The combination of nano-material and [...] Read more.

The prime objective of the research was to explore the coating effects of chitosan and nano-silicon dioxide with nisin as an antimicrobial agent on physicochemical properties, microbiological stability, and sensorial quality changes during the storage at 4 °C. The combination of nano-material and chitosan in addition to nisin was effective for reducing the postharvest attributes of fresh-cut cantaloupes in addition to the highest score in sensory evaluation. Chitosan coating treatment enhanced the microbiological quality 2.50 log CFU/g and 1.87 log CFU/g for aerobic counts and mold/yeasts populations, respectively. In a word, the combination of chitosan/nano-silica/nisin treatment was the best condition for fresh-cut cantaloupe shelf life extension by maintaining color, vitamin C 22.29 mg/100g, peroxidase activity 8.06 U/min.g, and other microbiological tests up to storage time of 8 days. Full article

(This article belongs to the Section Inorganic Membranes)

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33 pages, 2610 KiB

Open AccessReview

A Review on Polymer Nanocomposites and Their Effective Applications in Membranes and Adsorbents for Water Treatment and Gas Separation

by Oluranti Agboola, Ojo Sunday Isaac Fayomi, Ayoola Ayodeji, Augustine Omoniyi Ayeni, Edith E. Alagbe, Samuel E. Sanni, Emmanuel E. Okoro, Lucey Moropeng, Rotimi Sadiku, Kehinde Williams Kupolati and Babalola Aisosa Oni

Membranes 2021, 11(2), 139; https://doi.org/10.3390/membranes11020139 - 16 Feb 2021

Cited by 103 | Viewed by 9086

Abstract

Globally, environmental challenges have been recognised as a matter of concern. Among these challenges are the reduced availability and quality of drinking water, and greenhouse gases that give rise to change in climate by entrapping heat, which result in respirational illness from smog [...] Read more.

Globally, environmental challenges have been recognised as a matter of concern. Among these challenges are the reduced availability and quality of drinking water, and greenhouse gases that give rise to change in climate by entrapping heat, which result in respirational illness from smog and air pollution. Globally, the rate of demand for the use of freshwater has outgrown the rate of population increase; as the rapid growth in town and cities place a huge pressure on neighbouring water resources. Besides, the rapid growth in anthropogenic activities, such as the generation of energy and its conveyance, release carbon dioxide and other greenhouse gases, warming the planet. Polymer nanocomposite has played a significant role in finding solutions to current environmental problems. It has found interest due to its high potential for the reduction of gas emission, and elimination of pollutants, heavy metals, dyes, and oil in wastewater. The revolution of integrating developed novel nanomaterials such as nanoparticles, carbon nanotubes, nanofibers and activated carbon, in polymers, have instigated revitalizing and favourable inventive nanotechnologies for the treatment of wastewater and gas separation. This review discusses the effective employment of polymer nanocomposites for environmental utilizations. Polymer nanocomposite membranes for wastewater treatment and gas separation were reviewed together with their mechanisms. The use of polymer nanocomposites as an adsorbent for toxic metals ions removal and an adsorbent for dye removal were also discussed, together with the mechanism of the adsorption process. Patents in the utilization of innovative polymeric nanocomposite membranes for environmental utilizations were discussed. Full article

(This article belongs to the Special Issue Composite Membranes: Preparation and Applications)

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20 pages, 4037 KiB

Open AccessReview

Advanced Technologies for Stabilization and High Performance of Seawater RO Membrane Desalination Plants

by Hiroo Takabatake, Masahide Taniguchi and Masaru Kurihara

Membranes 2021, 11(2), 138; https://doi.org/10.3390/membranes11020138 - 16 Feb 2021

Cited by 27 | Viewed by 7274

Abstract

Seawater desalination plants that use reverse osmosis (RO) membranes have become a core part of social infrastructure, and should be designed to meet the needs of product water quality and production capacity, while considering various environmental factors such as the seawater quality, temperature [...] Read more.

Seawater desalination plants that use reverse osmosis (RO) membranes have become a core part of social infrastructure, and should be designed to meet the needs of product water quality and production capacity, while considering various environmental factors such as the seawater quality, temperature and geographical features. Furthermore, stable operation while overcoming various problems should be achieved alongside the increasing demands for energy saving and cost reduction. As no universal plant apparatus and operation technology meets these various requirements, the plants need to be customized for individual solutions. This paper reviews and summarizes the proven technologies, including their advantages/disadvantages, and points to cutting-edge technologies related to the design and operation maintenance of seawater intake, pre-treatment and the RO desalination process. Full article

(This article belongs to the Special Issue Seawater Reverse Osmosis Desalination)

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13 pages, 2590 KiB

Open AccessArticle

Comparison between Lipase Performance Distributed at the O/W Interface by Membrane Emulsification and by Mechanical Stirring

by Emma Piacentini, Rosalinda Mazzei and Lidietta Giorno

Membranes 2021, 11(2), 137; https://doi.org/10.3390/membranes11020137 - 16 Feb 2021

Cited by 12 | Viewed by 2622

Abstract

Multiphase bioreactors using interfacial biocatalysts are unique tools in life sciences such as pharmaceutical and biotechnology. In such systems, the formation of microdroplets promotes the mass transfer of reagents between two different phases, and the reaction occurs at the liquid–liquid interface. Membrane emulsification [...] Read more.

Multiphase bioreactors using interfacial biocatalysts are unique tools in life sciences such as pharmaceutical and biotechnology. In such systems, the formation of microdroplets promotes the mass transfer of reagents between two different phases, and the reaction occurs at the liquid–liquid interface. Membrane emulsification is a technique with unique properties in terms of precise manufacturing of emulsion droplets in mild operative conditions suitable to preserve the stability of bioactive labile components. In the present work, membrane emulsification technology was used for the production of a microstructured emulsion bioreactor using lipase as a catalyst and as a surfactant at the same time. An emulsion bioreaction system was also prepared by the stirring method. The kinetic resolution of (S,R)-naproxen methyl ester catalyzed by the lipase from Candida rugosa to obtain (S)-naproxen acid was used as a model reaction. The catalytic performance of the enzyme in the emulsion systems formulated with the two methods was evaluated in a stirred tank reactor and compared. Lipase showed maximum enantioselectivity (100%) and conversion in the hydrolysis of (S)-naproxen methyl ester when the membrane emulsification technique was used for biocatalytic microdroplets production. Moreover, the controlled formulation of uniform and stable droplets permitted the evaluation of lipase amount distributed at the interface and therefore the evaluation of enzyme specific activity as well as the estimation of the hydrodynamic radius of the enzyme at the oil/water (o/w) interface in its maximum enantioselectivity. Full article

(This article belongs to the Special Issue Membrane and Membrane Bioreactors Applied to Health and Life Sciences)

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24 pages, 4338 KiB

Open AccessArticle

Understanding of Adsorption and Desorption Mechanisms of Anthocyanins and Proanthocyanidins on Heterogeneous and Homogeneous Cation-Exchange Membranes

by Véronique Perreault, Veronika Sarapulova, Ksenia Tsygurina, Natalia Pismenskaya and Laurent Bazinet

Membranes 2021, 11(2), 136; https://doi.org/10.3390/membranes11020136 - 16 Feb 2021

Cited by 13 | Viewed by 2406

Abstract

The presence of membrane fouling is the main drawback in membrane processes, and it is related to the premature use and high cost for the replacement of membranes. Polyphenols in cranberry juice are associated with ion-exchange membrane fouling, and it results in a [...] Read more.

The presence of membrane fouling is the main drawback in membrane processes, and it is related to the premature use and high cost for the replacement of membranes. Polyphenols in cranberry juice are associated with ion-exchange membrane fouling, and it results in a loss of these beneficial compounds in the juice when treated by membrane processes such as electrodialysis. In the present work, four heterogeneous or pseudohomogeneous cation-exchange membranes (CSE-fg, MK-40, CEM Type-II, and CJMC-5), different in terms of the polymer matrix (aromatic, aliphatic), exchange capacity, size, and location of meso and macropores, were studied to understand the impact of the membrane structure and physico-chemical properties on adsorption and desorption of phenolic compounds (anthocyanins and proanthocyanidins) from cranberry juice. It appeared from these results that MK-40, CEM Type-II, and CSE-fg were more prone to fouling due to their high ion-exchange capacity, their thickness, and the presence of meso and macropores in their structure. Indeed, electrostatic interactions occurred between fixed groups of membranes and polyphenolic ions. Desorption of the entire membrane and cryogenic grinding with pH adjusted to 10 allowed a better recovery of anthocyanins and proanthocyanidins (PACs), respectively, since hydroxide ions competed with polyphenols and membrane that induced desorption of polyphenols. In the future, this new knowledge will become the basis for a more sensible choice of membranes and for the development of protocols for extending their life cycle. Full article

(This article belongs to the Special Issue Ion-Exchange Membranes and Processes (Volume II))

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22 pages, 7308 KiB

Open AccessArticle

The Influence of Concentration and Temperature on the Membrane Resistance of Ion Exchange Membranes and the Levelised Cost of Hydrogen from Reverse Electrodialysis with Ammonium Bicarbonate

by Yash Dharmendra Raka, Robert Bock, Håvard Karoliussen, Øivind Wilhelmsen and Odne Stokke Burheim

Membranes 2021, 11(2), 135; https://doi.org/10.3390/membranes11020135 - 16 Feb 2021

Cited by 18 | Viewed by 3890

Abstract

The ohmic resistances of the anion and cation ion-exchange membranes (IEMs) that constitute a reverse electrodialysis system (RED) are of crucial importance for its performance. In this work, we study the influence of concentration (0.1 M, 0.5 M, 1 M and 2 M) [...] Read more.

The ohmic resistances of the anion and cation ion-exchange membranes (IEMs) that constitute a reverse electrodialysis system (RED) are of crucial importance for its performance. In this work, we study the influence of concentration (0.1 M, 0.5 M, 1 M and 2 M) of ammonium bicarbonate solutions on the ohmic resistances of ten commercial IEMs. We also studied the ohmic resistance at elevated temperature 313 K. Measurements have been performed with a direct two-electrode electrochemical impedance spectroscopy (EIS) method. As the ohmic resistance of the IEMs depends linearly on the membrane thickness, we measured the impedance for three different layered thicknesses, and the results were normalised. To gauge the role of the membrane resistances in the use of RED for production of hydrogen by use of waste heat, we used a thermodynamic and an economic model to study the impact of the ohmic resistance of the IEMs on hydrogen production rate, waste heat required, thermochemical conversion efficiency and the levelised cost of hydrogen. The highest performance was achieved with a stack made of FAS30 and CSO Type IEMs, producing hydrogen at 8.48× 10

^{- 7}

kg m

_{m e m}^{- 2}

s

^{- 1}

with a waste heat requirement of 344 kWh kg

^{- 1}

hydrogen. This yielded an operating efficiency of 9.7% and a levelised cost of 7.80 € kg

_{H_{2}}^{- 1}

. Full article

(This article belongs to the Special Issue Advanced Membrane Technology on Desalination and Concentration)

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9 pages, 2788 KiB

Open AccessArticle

Preparation and Properties of Crystalline IGZO Thin Films

by Xiao Wang, Zhihua Shen, Jie Li and Shengli Wu

Membranes 2021, 11(2), 134; https://doi.org/10.3390/membranes11020134 - 14 Feb 2021

Cited by 11 | Viewed by 4722

Abstract

IGZO thin films can be used as active layers of thin-film transistors and have been widely studied. However, amorphous indium gallium zinc oxide (IGZO) fabricated at room temperature is vulnerable in subsequent manufacturing processes, such as etching and sputtering; this limits IGZO thin [...] Read more.

IGZO thin films can be used as active layers of thin-film transistors and have been widely studied. However, amorphous indium gallium zinc oxide (IGZO) fabricated at room temperature is vulnerable in subsequent manufacturing processes, such as etching and sputtering; this limits IGZO thin film transistors’ (TFTs) use in commercial products. In this paper, we prepared a c-axis crystallized IGZO thin film by Radio Frequency (RF) sputtering at 180 °C, with a 50% O₂ ratio and 110 W power. XRD images show that the crystallized film has an obvious diffraction peak near 31°, and the spacing between the crystal surfaces was calculated to be ≈0.29 nm. The HRTEM map confirmed the above results. The stability of IGZO thin films was investigated by etching them with an acid solution. The crystalline IGZO films exhibited better acid corrosion resistance, and their anticorrosion performance was 74% higher than that of amorphous IGZO (a-IGZO) films, indicating the crystalline IGZO film can provide more stable performance in applications. Full article

(This article belongs to the Special Issue Application of Ferroelectric-Polymer Composites)

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18 pages, 3599 KiB

Open AccessArticle

Higher Acid Recovery Efficiency of Novel Functionalized Inorganic/Organic Composite Anion Exchange Membranes from Acidic Wastewater

by Muhammad Imran Khan, Abdallah Shanableh, Noureddine Elboughdiri, Karim Kriaa, Djamel Ghernaout, Saad Ghareba, Majeda Khraisheh and Mushtaq Hussain Lashari

Membranes 2021, 11(2), 133; https://doi.org/10.3390/membranes11020133 - 14 Feb 2021

Cited by 13 | Viewed by 3165

Abstract

In this work, the synthesis of a series of the functionalized inorganic/organic composite anion exchange membranes (AEMs) was carried out by employing the varying amount of inorganic filler consist of N-(trimethoxysilylpropyl)-N,N,N-trimethylammonium chloride (TMSP-TMA⁺Cl⁻ [...] Read more.

In this work, the synthesis of a series of the functionalized inorganic/organic composite anion exchange membranes (AEMs) was carried out by employing the varying amount of inorganic filler consist of N-(trimethoxysilylpropyl)-N,N,N-trimethylammonium chloride (TMSP-TMA⁺Cl⁻) into the quaternized poly (2, 6-dimethyl-1, 4-phenylene oxide) (QPPO) matrix for acid recovery via diffusion dialysis (DD) process. Fourier transform infrared (FTIR) spectroscopy clearly demonstrated the fabrication of the functionalized inorganic/organic composite AEMs and the subsequent membrane characteristic measurements such as ion exchange capacity (IEC), linear swelling ratio (LSR), and water uptake (W_R) gave us the optimum loading condition of the filler without undesirable filler particle aggregation. These composite AEMs exhibited IEC of 2.18 to 2.29 meq/g, LSR of 13.33 to 18.52%, and W_R of 46.11 to 81.66% with sufficient thermal, chemical, and mechanical stability. The diffusion dialysis (DD) test for acid recovery from artificial acid wastewater of HCl/FeCl₂ showed high acid DD coefficient (U_H⁺) (0.022 to 0.025 m/h) and high separation factor (S) (139-260) compared with the commercial membrane. Furthermore, the developed AEMs was acceptably stable (weight loss < 20%) in the acid wastewater at 60 °C as an accelerated severe condition for 2 weeks. These results clearly indicated that the developed AEMs have sufficient potential for acid recovery application by DD process. Full article

(This article belongs to the Special Issue Ion-Exchange Membranes and Processes (Volume II))

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17 pages, 1681 KiB

Open AccessArticle

Study of Resveratrol’s Interaction with Planar Lipid Models: Insights into Its Location in Lipid Bilayers

by Daniela Meleleo

Membranes 2021, 11(2), 132; https://doi.org/10.3390/membranes11020132 - 14 Feb 2021

Cited by 18 | Viewed by 2668

Abstract

Resveratrol, a polyphenolic molecule found in edible fruits and vegetables, shows a wide range of beneficial effects on human health, including anti-microbial, anti-inflammatory, anti-cancer, and anti-aging properties. Due to its poor water solubility and high liposome-water partition coefficient, the biomembrane seems to be [...] Read more.

Resveratrol, a polyphenolic molecule found in edible fruits and vegetables, shows a wide range of beneficial effects on human health, including anti-microbial, anti-inflammatory, anti-cancer, and anti-aging properties. Due to its poor water solubility and high liposome-water partition coefficient, the biomembrane seems to be the main target of resveratrol, although the mode of interaction with membrane lipids and its location within the cell membrane are still unclear. In this study, using electrophysiological measurements, we study the interaction of resveratrol with planar lipid membranes (PLMs) of different composition. We found that resveratrol incorporates into palmitoyl-oleoyl-phosphatidylcholine (POPC) and POPC:Ch PLMs and forms conductive units unlike those found in dioleoyl-phosphatidylserine (DOPS):dioleoyl-phosphatidylethanolamine (DOPE) PLMs. The variation of the biophysical parameters of PLMs in the presence of resveratrol provides information on its location within a lipid double layer, thus contributing to an understanding of its mechanism of action. Full article

(This article belongs to the Special Issue Electrical Properties of Model Lipid Membranes)

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15 pages, 890 KiB

Open AccessReview

Cleaning Methods for Ceramic Ultrafiltration Membranes Affected by Organic Fouling

by Kamila Gruskevica and Linda Mezule

Membranes 2021, 11(2), 131; https://doi.org/10.3390/membranes11020131 - 14 Feb 2021

Cited by 37 | Viewed by 7199

Abstract

The use of ceramic membranes in the treatment and processing of various liquids, including those of organic origin, has increased tremendously at the industrial level. Apart from the selection of the most appropriate membrane materials and operational conditions, suitable membrane cleaning procedures are [...] Read more.

The use of ceramic membranes in the treatment and processing of various liquids, including those of organic origin, has increased tremendously at the industrial level. Apart from the selection of the most appropriate membrane materials and operational conditions, suitable membrane cleaning procedures are a must to minimize fouling and increase membrane lifespan. The review summarizes currently available and practiced non-reagent and cleaning-in-place methods for ceramic membranes that are used in the treatment of organic liquids, thus causing organic fouling. Backflushing, backwashing, and ultrasound represent the most often used physical methods for reversible fouling treatment. At the same time, the use of alkalis, e.g, sodium hydroxide, acids, or strong oxidants are recommended for cleaning of irreversible fouling treatment. Full article

(This article belongs to the Section Inorganic Membranes)

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21 pages, 8050 KiB

Open AccessArticle

Runge–Kutta Numerical Method Followed by Richardson’s Extrapolation for Efficient Ion Rejection Reassessment of a Novel Defect-Free Synthesized Nanofiltration Membrane

by Chabi Noël Worou, Jing Kang, Jimin Shen, Pengwei Yan, Weiqiang Wang, Yingxu Gong and Zhonglin Chen

Membranes 2021, 11(2), 130; https://doi.org/10.3390/membranes11020130 - 14 Feb 2021

Cited by 7 | Viewed by 2423

Abstract

A defect-free, loose, and strong layer consisting of zirconium (Zr) nanoparticles (NPs) has been successfully established on a polyacrylonitrile (PAN) ultrafiltration substrate by an in-situ formation process. The resulting organic–inorganic nanofiltration (NF) membrane, NF-PANZr, has been accurately characterized not only with regard to [...] Read more.

A defect-free, loose, and strong layer consisting of zirconium (Zr) nanoparticles (NPs) has been successfully established on a polyacrylonitrile (PAN) ultrafiltration substrate by an in-situ formation process. The resulting organic–inorganic nanofiltration (NF) membrane, NF-PANZr, has been accurately characterized not only with regard to its properties but also its structure by the atomic force microscopy, field emission scanning electron microscopy, and energy dispersive spectroscopy. A sophisticated computing model consisting of the Runge–Kutta method followed by Richardson extrapolation was applied in this investigation to solve the extended Nernst–Planck equations, which govern the solute particles’ transport across the active layer of NF-PANZr. A smart, adaptive step-size routine is chosen for this simple and robust method, also known as RK4 (fourth-order Runge–Kutta). The NF-PANZr membrane was less performant toward monovalent ions, and its rejection rate for multivalent ions reached 99.3%. The water flux of the NF-PANZr membrane was as high as 58 L · m⁻² · h⁻¹. Richardson’s extrapolation was then used to get a better approximation of Cl⁻ and Mg²⁺ rejection, the relative errors were, respectively, 0.09% and 0.01% for Cl⁻ and Mg²⁺. While waiting for the rise and expansion of machine learning in the prediction of rejection performance, we strongly recommend the development of better NF models and further validation of existing ones. Full article

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13 pages, 433 KiB

Open AccessArticle

Debye-Hückel Free Energy of an Electric Double Layer with Discrete Charges Located at a Dielectric Interface

by Guilherme Volpe Bossa and Sylvio May

Membranes 2021, 11(2), 129; https://doi.org/10.3390/membranes11020129 - 14 Feb 2021

Cited by 8 | Viewed by 2677

Abstract

Poisson–Boltzmann theory provides an established framework to calculate properties and free energies of an electric double layer, especially for simple geometries and interfaces that carry continuous charge densities. At sufficiently small length scales, however, the discreteness of the surface charges cannot be neglected. [...] Read more.

Poisson–Boltzmann theory provides an established framework to calculate properties and free energies of an electric double layer, especially for simple geometries and interfaces that carry continuous charge densities. At sufficiently small length scales, however, the discreteness of the surface charges cannot be neglected. We consider a planar dielectric interface that separates a salt-containing aqueous phase from a medium of low dielectric constant and carries discrete surface charges of fixed density. Within the linear Debye-Hückel limit of Poisson–Boltzmann theory, we calculate the surface potential inside a Wigner–Seitz cell that is produced by all surface charges outside the cell using a Fourier-Bessel series and a Hankel transformation. From the surface potential, we obtain the Debye-Hückel free energy of the electric double layer, which we compare with the corresponding expression in the continuum limit. Differences arise for sufficiently small charge densities, where we show that the dominating interaction is dipolar, arising from the dipoles formed by the surface charges and associated counterions. This interaction propagates through the medium of a low dielectric constant and alters the continuum power of two dependence of the free energy on the surface charge density to a power of 2.5 law. Full article

(This article belongs to the Special Issue Electrostatics in Cell Membranes and in Artificial Membrane Models)

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35 pages, 6419 KiB

Open AccessArticle

The Need for Accurate Osmotic Pressure and Mass Transfer Resistances in Modeling Osmotically Driven Membrane Processes

by Endre Nagy, Imre Hegedüs, Danyal Rehman, Quantum J. Wei, Yvana D. Ahdab and John H. Lienhard

Membranes 2021, 11(2), 128; https://doi.org/10.3390/membranes11020128 - 14 Feb 2021

Cited by 18 | Viewed by 4068

Abstract

The widely used van ’t Hoff linear relation for predicting the osmotic pressure of NaCl solutions may result in errors in the evaluation of key system parameters, which depend on osmotic pressure, in pressure-retarded osmosis and forward osmosis. In this paper, the linear [...] Read more.

The widely used van ’t Hoff linear relation for predicting the osmotic pressure of NaCl solutions may result in errors in the evaluation of key system parameters, which depend on osmotic pressure, in pressure-retarded osmosis and forward osmosis. In this paper, the linear van ’t Hoff approach is compared to the solutions using OLI Stream Analyzer, which gives the real osmotic pressure values. Various dilutions of NaCl solutions, including the lower solute concentrations typical of river water, are considered. Our results indicate that the disparity in the predicted osmotic pressure of the two considered methods can reach 30%, depending on the solute concentration, while that in the predicted power density can exceed over 50%. New experimental results are obtained for NanoH2O and Porifera membranes, and theoretical equations are also developed. Results show that discrepancies arise when using the van ’t Hoff equation, compared to the OLI method. At higher NaCl concentrations (C > 1.5 M), the deviation between the linear approach and the real values increases gradually, likely indicative of a larger error in van ’t Hoff predictions. The difference in structural parameter values predicted by the two evaluation methods is also significant; it can exceed the typical 50–70% range, depending on the operating conditions. We find that the external mass transfer coefficients should be considered in the evaluation of the structural parameter in order to avoid overestimating its value. Consequently, measured water flux and predicted structural parameter values from our own and literature measurements are recalculated with the OLI software to account for external mass transfer coefficients. Full article

(This article belongs to the Special Issue Numerical Modelling in Membrane Processes)

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