Membrane Fabrication Process Research Articles

Lead-imprinted polyvinylidene fluoride membrane for selective removal of lead from contaminated water: material fabrication, filtration application, and mechanism study.

The drinking water has become contaminated with lead in many countries across the world. In this study, a novel lead-imprinted polyvinylidene fluoride (PVDF) membrane was successfully fabricated for selective decontamination of lead from water. First of all, the membrane fabrication process was explored and optimized. The physical and chemical properties were then studied for a better understanding of the features of the membrane. The performance of lead removal by the adsorptive membrane was evaluated by systematic batch adsorption experiments, including pH effect, kinetics, isotherm, selectivity, and regeneration studies. The results indicated that the adsorptive membrane showed a high adsorption capacity of 40.59 mg Pb/g at the optimal pH of 5.5, fast kinetics of 2 h, high selectivity towards lead, and outstanding regeneration performance. The Langmuir equation fitted the isotherm better than the Freundlich equation, while the pseudo-second-order model and pore diffusion model well described the kinetics. The adsorptive membrane showed high selectivity towards lead in the lead/zinc binary solution. In the continuous filtration study, a small piece of adsorptive membrane could treat 3.75 L of lead solution. The XPS studies revealed that the lead uptake was mainly due to the complex reaction between lead and carboxyl and hydroxyl in the membrane.

Lyotropic Liquid Crystal (LLC)-Templated Nanofiltration Membranes by Precisely Administering LLC/Substrate Interfacial Structure

Mesoporous materials based on lyotropic liquid crystal templates with precisely defined and flexible nanostructures offer an alluring solution to the age-old challenge of water scarcity. In contrast, polyamide (PA)-based thin-film composite (TFC) membranes have long been hailed as the state of the art in desalination. They grapple with a common trade-off between permeability and selectivity. However, the tides are turning as these novel materials, with pore sizes ranging from 0.2 to 5 nm, take center stage as highly coveted active layers in TFC membranes. With the ability to regulate water transport and influence the formation of the active layer, the middle porous substrate of TFC membranes becomes an essential player in unlocking their true potential. This review delves deep into the recent advancements in fabricating active layers using lyotropic liquid crystal templates on porous substrates. It meticulously analyzes the retention of the liquid crystal phase structure, explores the membrane fabrication processes, and evaluates the water filtration performance. Additionally, it presents an exhaustive comparison between the effects of substrates on both polyamide and lyotropic liquid crystal template top layer-based TFC membranes, covering crucial aspects such as surface pore structures, hydrophilicity, and heterogeneity. To push the boundaries even further, the review explores a diverse array of promising strategies for surface modification and interlayer introduction, all aimed at achieving an ideal substrate surface design. Moreover, it delves into the realm of cutting-edge techniques for detecting and unraveling the intricate interfacial structures between the lyotropic liquid crystal and the substrate. This review is a passport to unravel the enigmatic world of lyotropic liquid crystal-templated TFC membranes and their transformative role in global water challenges.

Fabrication and Evaluation of Filtration Membranes from Industrial Polymer Waste

Polyvinylidene fluoride (PVDF) polymers are known for their diverse range of industrial applications and are considered important raw materials for membrane manufacturing. In view of circularity and resource efficiency, the present work mainly deals with the reusability of waste polymer 'gels' produced during the manufacturing of PVDF membranes. Herein, solidified PVDF gels were first prepared from polymer solutions as model waste gels, which were then subsequently used to prepare membranes via the phase inversion process. The structural analysis of fabricated membranes confirmed the retention of molecular integrity even after reprocessing, whereas the morphological analysis showed a symmetric bi-continuous porous structure. The filtration performance of membranes fabricated from waste gels was studied in a crossflow assembly. The results demonstrate the feasibility of gel-derived membranes as potential microfiltration membranes exhibiting a pure water flux of 478 LMH with a mean pore size of ~0.2 µm. To further evaluate industrial applicability, the performance of the membranes was tested in the clarification of industrial wastewater, and the membranes showed good recyclability with about 52% flux recovery. The performance of gel-derived membranes thus demonstrates the recycling of waste polymer gels for improving the sustainability of membrane fabrication processes.

Research progress on the substrate for metal–organic framework (MOF) membrane growth for separation

During the last decade, metal–organic frameworks (MOFs) have been applied in various fields due to their unique chemical and functional advantages. One of the widespread research hotspots is MOF-based membranes for separations, specifically continuous defect-free MOF membranes, which are usually grown on porous substrates. The substrate not only serves as the MOF layer support but also has a great influence on the membrane fabrication process and the final separation performance of the resultant membrane. In this review, we mainly introduce the progress focused on the substrates for MOF membranes fabrication. The substrate modifications and seeding methods aimed at synthesizing high-quality MOF membranes are also summarized systematically.

Effect of Polyvinylpyrrolidone on Polyvinylidene Fluoride/Hydroxyapatite- Blended Nanofiltration Membranes: Characterization and Filtration Properties.

The application of polyvinylidene fluoride (PVDF) as a filtration membrane is limited due to its hydrophobicity. This paper elaborated on the fabrication process of nanofiltration PVDF membrane incorporating various quantities of hydrophilic polyvinylpyrrolidone (PVP) and hydroxyapatite (HA) using a wet phase inversion method to improve its hydrophilicity. The membrane was fabricated by using the wet phase inversion method. It was then characterized in terms of water permeability, water contact angle, water content, surface energy, and surface porosity. Bacteria and Fe ions filtration was conducted to investigate the membrane filtration performance. The PVDF/PVP/HA-blended membrane showed the highest water permeability (6,165 LMH/Bar), water content (45.2 %), and surface energy (104.1 mN/m) when 2 wt.% of PVP was introduced into the base polymer PVDF. This fabricated membrane, labeled as PVP 2.0, also showed the lowest contact angle (64°) and the highest surface porosity (42%). Overall, the PVP introduction patents into the polymeric membrane doping solution potentially improves membrane hydrophilicity and permeability.

In-situ coating of Fe-TA complex on thin-film composite membranes for improved water permeance in reverse osmosis desalination

Post-modifications of thin-film composite (TFC) reverse osmosis (RO) membranes have been extensively studied to improve the overall separation performance. However, new approaches have yet to be explored not only to achieve better separation efficiency, but also to reduce the overall manufacturing cost. In this work, a ferric-tannic acid (Fe-TA) complex is post-coated onto the bare TFC membranes in an in-situ stepwise process. By optimizing the concentrations of Fe3+ and TA, the resulting membrane can achieve a water permeance of 3.58 L m−2 h−1 bar−1 (LMH bar−1) and a salt rejection of 98.37 % at 20 bar for brackish water desalination, owing to the improved surface hydrophilicity, roughness and additional water pathways. Moreover, the optimal membrane also exhibits comparable performance in seawater desalination and boron removal. This new approach of modification shows potentials to be integrated into the current roll-to-roll membrane fabrication process.

Morphological transformation of perfluorinated sulfonic acid ionomer via ionic complex formation at a high entropy state

Proton exchange membranes (PEMs) act as conductors in PEM fuel cells (PEMFCs) to transport protons from the anode to the cathode in the membrane electrode assembly (MEA). Because protons are transported via the hydrophilic channels of the PEMs, the morphological control of these channels has been considered a key issue that influences their electrochemical performance. In this study, we propose a simple route that provides fast proton transport pathways via the morphological transformation of hydrophilic channels in a commercially available perfluorinated sulfonic acid (PFSA) ionomer, Nafion®. It is based on the formation of ionic complexes when metallic salts are added during the membrane fabrication process, instead of using PFSA ionomers with tuned chemical structures. The effectiveness of this strategy is theoretically verified by performing molecular simulations for the ionic cluster formation mechanism. The formation of the ionic complexes in a high entropy state is found to be advantageous in decreasing the distance between ionic clusters, improving proton transport efficiency resulting in higher proton conductivity and single cell performance without any additional chemical and processing step causing the production cost increase.

Comparing the environmental impacts of using bio-renewable and fossil-derived solvent in polymer membrane fabrications

Sustainable production methods for polymer membrane fabrication are gaining attention due to concerns about the toxicity of conventional fossil-derived solvents in the production process. In addition, the promotion of using chemicals from renewable source for synthesis processes among industries and researches has increased to decelerate resource depletion. As such, more benign and bio-renewable solvents, dihydrolevoglucosenone (Cyrene™) and 2-methyltetrahydrofuran (2-MeTHF), have been proposed as replacements for traditional fossil-derived solvents, n-hexane and dimethylformamide (DMF). In this work, a life cycle assessment (LCA) was employed to quantitatively evaluate the environmental impacts of using the aforementioned bio-renewable solvents versus fossil-derived solvents for fabricating 1 ​g of polymer membrane. The analysis adopted a cradle-to-gate perspective and assessed three endpoint impact categories: Human health, Ecosystems and Resources. Despite lower environmental impacts for producing bio-renewable solvents, using such solvents to fabricate membranes displayed a higher environmental impact score in all endpoint categories. This discrepancy was attributed to the lower yield of the membrane fabrication process when using bio-based solvents. This indicated that further work is needed to optimise membrane fabrication so that the benefits of using bio-based solvents can be maximised.

Effective regulating interfacial polymerization process of OSN membrane via in-situ constructed nano-porous interlayer of 2D TpHz covalent organic frameworks

In this study, a kind of thin film composite (TFC) membrane with two-dimensional (2D) covalent organic frameworks (COFs) as interlayer, termed as iTFC, which has integrally covalent bonding structure, ultra-thin and ultra-smooth surface, as well as high separation performance was fabricated via interfacial polymerization (IP) and subsequent chemical cross-linking and solvent activation for organic solvent nanofiltration (OSN). The COFs interlayer was in situ constructed using 1,3,5-triformylphloroglucinol (Tp) and hydrazine (Hz) on polyimide (PI) substrate prior to the IP. The optimization of the membrane fabrication process shows that very low concentration for both the COFs aqueous monomer Hz and the IP aqueous monomer m-phenylenediamine (MPD) was conducive to the formation of very smooth (roughness of 2.4 nm), very thin and defect-free cortex, thus improving the organic solvent permeation while remaining the dye rejection. Under optimal conditions, the prepared iTFC OSN membrane has an ethanol permeance of 63.4 L m−2 h−1 MPa−1, a Rhodamine B (RDB) rejection of greater than 99 %, and a molecular weight cut-off (MWCO) of as low as 380 Da. In addition, after filtration of 100 mg L−1 RB/DMF solution for 408 h, the optimized iTFC OSN membrane remained Rose Bengal (RB) rejection above 97 %, which proves its excellent solvent resistance performance.

Polymeric Materials and Microfabrication Techniques for Liquid Filtration Membranes.

This review surveys and summarizes the materials and methods used to make liquid filtration membranes. Examples of each method including phase inversion, electrospinning, interfacial polymerization, thin film composites, stretching, lithography and templating techniques, are given and the pros and cons of each method are discussed. Trends of recent literature are also discussed and their potential direction is deliberated. Furthermore, the polymeric materials used in the fabrication process of liquid filtration membranes are also reviewed and trends and similarities are shown and discussed. Thin film composites and selective filtration applications appear to be a growing area of research for membrane technology. Other than the required mechanical properties (tensile strength, toughness and chemical and thermal stability), it becomes apparent that polymer solubility and hydropathy are key factors in determining their applicability for use as a membrane material.

Ion-exchange membranes for blue energy generation: A short overview focused on nanocomposite

Blue energy can be harvested from salinity gradients between saline water and freshwater by reverse electrodialysis (RED). RED as a conversion technique to generate blue energy has received increasing attention in recent decades. As part of the RED system, ion exchange membranes (IEMs) are key elements to the success of future blue energy generation. However, its suboptimal performance often limits the applications and stagnates the deve­lopment of the technology. The key properties of IEMs include ion exchange capacity, perm­selectivity, and electrical resistance. The enhancement of such physical and electrochemical properties is crucial for studying energy production with acceptable output efficiency on a commercial scale. Recently, many studies have tried blending nanotechnology into the membrane fabrication process. Hybridizing inorganic nanomaterials with an organic polymeric material showed the great potential of improving electrical conductivity and perm­selectivity, as well as other membrane characteristics for power performance. In this short review, recent developments on the IEM synthesis in association with potential nanomaterials are reviewed and raising issues regarding the application and commercialization of RED-based energy production are discussed.

(Invited) Electrified Membranes for Transformation of Nitrate in Wastewaters

The release of nitrate to the environment from wastewater effluent and agricultural runoff contributes to groundwater contamination, harmful algal blooms, and disruption of biogeochemical nitrogen flows. Typical treatment methods are based on nitrate separation, which produces waste streams that are often discharged to the environment. Alternatively, nitrate conversion via electrochemical reduction eliminates the production of concentrated waste streams while avoiding the addition of reductant or hole scavenger chemicals to accomplish the reaction. However, major challenges for nitrate removal from water via electrochemical conversion involve reducing the use of expensive precious metal electrocatalysts while also improving the reaction activity and selectivity, catalyst stability, and mass transport of nitrate to electrocatalyst active sites. The use of electrochemical membranes as multifunctional porous flow-through electrodes could potentially address these challenges based on improved mass transport and altered kinetics under flow conditions within membrane pores.Conductive membranes were fabricated using polymers combined with carbonaceous materials such as reduced graphene oxide (rGO) and carbon nanotubes. The rGO was functionalized with non-precious transition metal oxynitride electrocatalysts, where these catalysts showed higher nitrate conversion activity compared to the unsupported transition metal nitrides. The influence of catalyst materials, membrane fabrication process, and filtration conditions on nitrate reduction activity and selectivity were evaluated. In addition to the environmental impacts of closing the nitrogen loop by converting nitrate into innocuous N2, selective nitrate reduction to ammonia provides opportunities for recovery as fertilizer or carbon-free renewable energy storage. The prospects for reactive nitrogen recovery based on nitrate electrochemical conversion to ammonia were analyzed for various potential source waters.

(Invited, Digital Presentation) Polybenzimidazole and Its Use in Energy Storage and Conversion

Polybenzimidazole (PBI) is a unique polymer. It has high mechanical strength and stability, and is not conductive. However, in contact with acids, the imidazole rings are protonated, and PBI becomes proton conductive. In contact with alkaline solutions, the amine groups are deprotonated, and PBI becomes hydroxide conductive. Control of the doping process allows to adjust the uptake and hence allows to control conductivity and permeability of PBI membranes. Therefore, PBI can be used in various ways for several applications. Phosphoric acid doped PBI blends were tested in the HT PEMFC, and showed more than >2000 hours stable, high performance operation at very challenging high current density of 800 mA/cm2 (one of world-best results).[1] Sulfuric acid doped PBI membranes were developed for use in the vanadium redox flow battery. We show that stable performances with an energy efficiency >91% and coulomb efficiency >99% @ 80 mA/cm2 can be achieved, which is one of the highest reported performances.[2, 3] By using a newly developed membrane fabrication process, hydroxide conducting membranes with a conductivity of > 310 mS/cm2 were be obtained. Porous supports enhanced the mechanical stability of these membranes, and PEM-water electrolyser-like performance was achieved in an alkaline water electrolyser, which was successfully operated for 1000 hours without failure.[4] A common way to increase the mechanical stability of membranes is reinforcement with a porous support. The drawback is that different swelling ratios of matrix and support can form voids, which results in unacceptably high gas crossover in electrolyzers and fuel cells. To tackle this issue, we pore filled an electrospun PBI fiber mat with a bomoalkylated polymer and reacted it with the imidazole groups available on the PBI fiber surface, thus forming a covalently bonded interface. In a final step, the remaining bromoalkyl groups were quaternized. The membrane was tested for 200 hours in an electrolyzer, and showed no signs of degradation. [5] [1] N. Nambi Krishnan, N.M.H. Duong, A. Konovalova, J.H. Jang, H.S. Park, H.J. Kim, A. Roznowska, A. Michalak, D. Henkensmeier, Polybenzimidazole / tetrazole-modified poly(arylene ether) blend membranes for high temperature proton exchange membrane fuel cells, J. Membr. Sci., 2020, 614, 118494. https://doi.org/10.1016/j.memsci.2020.118494[2] C. Noh, D. Serhiichuk, M. Najibah, Y. Kwon, D. Henkensmeier, Optimizing the performance of meta-polybenzimidazole membranes in vanadium redox flow batteries by adding an alkaline pre-swelling step, Chem. Eng, J., 405 (2021) 126574. https://doi.org/10.1016/j.cej.2020.126574[3] unpublished results[4] under review[5] Malikah Najibah, E. Tsoy, H. Khalid, Y. Chen, Q. Li, C. Bae, J. Hnát, M. Plevová, K. Bouzek, J.H. Jang, H.S. Park, Dirk Henkensmeier, PBI nanofiber mat-reinforced anion exchange membranes with covalently linked interfaces for use in water electrolysers, J. Membr. Sci., 2021, 640, 119832. https://doi.org/10.1016/j.memsci.2021.119832

Challenges, Opportunities and Future Directions of Membrane Technology for Natural Gas Purification: A Critical Review.

Natural gas is an important and fast-growing energy resource in the world and its purification is important in order to reduce environmental hazards and to meet the required quality standards set down by notable pipeline transmission, as well as distribution companies. Therefore, membrane technology has received great attention as it is considered an attractive option for the purification of natural gas in order to remove impurities such as carbon dioxide (CO2) and hydrogen sulphide (H2S) to meet the usage and transportation requirements. It is also recognized as an appealing alternative to other natural gas purification technologies such as adsorption and cryogenic processes due to its low cost, low energy requirement, easy membrane fabrication process and less requirement for supervision. During the past few decades, membrane-based gas separation technology employing hollow fibers (HF) has emerged as a leading technology and underwent rapid growth. Moreover, hollow fiber (HF) membranes have many advantages including high specific surface area, fewer requirements for maintenance and pre-treatment. However, applications of hollow fiber membranes are sometimes restricted by problems related to their low tensile strength as they are likely to get damaged in high-pressure applications. In this context, braid reinforced hollow fiber membranes offer a solution to this problem and can enhance the mechanical strength and lifespan of hollow fiber membranes. The present review includes a discussion about different materials used to fabricate gas separation membranes such as inorganic, organic and mixed matrix membranes (MMM). This review also includes a discussion about braid reinforced hollow fiber (BRHF) membranes and their ability to be used in natural gas purification as they can tackle high feed pressure and aggressive feeds without getting damaged or broken. A BRHF membrane possesses high tensile strength as compared to a self-supported membrane and if there is good interfacial bonding between the braid and the separation layer, high tensile strength, i.e., upto 170Mpa can be achieved, and due to these factors, it is expected that BRHF membranes could give promising results when used for the purification of natural gas.

Development and Industrial-Scale Fabrication of Next-Generation Low-Energy Membranes for Desalination

Spiral-wound modules have been the most common configuration of packing flat-sheet membranes since the early development of polyamide (PA) membranes for water treatment applications. Conventional spiral-wound modules (SWMs) for desalination applications typically consist of several leaf sets, with each leaf set comprising feed spacers, membranes, and a permeate carrier (PC) wrapped around a permeate-collecting tube. The membrane area that can be packed into a given module diameter is limited by the overall leaf set thickness, restricting module productivity for a given membrane permeability. We describe here a novel industrial-scale method for successfully coating the polysulfone (PSf) ultrafiltration (UF) support layer directly onto a permeate carrier, instead of conventional non-woven fabric, as a precursor to the polyamide TFC coating, resulting in twofold benefits: (a) drastically simplifying the membrane fabrication process by eliminating the use of non-woven fabric and (b) increasing the throughput of each membrane module by facilitating the packing of a larger membrane area in a standard module housing. By combining the permeate carrier and membrane into a single sheet, the need for the non-woven support layer was eliminated, leading to a significantly reduced leaf set thickness, enabling a much larger membrane area to be packed in a given volume, leading to lower energy consumption per cubic meter of produced water. Molecular-weight cutoff (MWCO) values in the range of 36–96 kDa were found to be dependent on PC thickness and material. Nevertheless, the reinforced membranes were successfully fabricated with a ~9% reduction in membrane leaf thickness compared to a conventional membrane. Preliminary trials of coating a thin-film composite PA layer resulted in defect-free reverse osmosis (RO) membranes with a salt rejection of 94% and a flux of 40 L m−2 h−1 when tested against a 2000 mg/L NaCl feed solution at an operating pressure of 15 bar. Results from the testing of the 1812 and 2514 elements validated the novel concept and paved the way for further improvements towards full-scale RO membranes with the potential to be the next low-energy workhorse of the water industry.

Using the dimethyl sulfoxide green solvent for the making of antifouling PEGylated membranes by the vapor-induced phase separation process

The toxicity of common solvents used in membrane fabrication threatens the environmental sustainability and questions the claim that membrane technology is a green separation technology. Therefore, there is a need for re-orienting membrane fabrication processes towards greener solutions, making use of less toxic, and possibly environmentally friendly solvents. We employed dimethyl sulfoxide (DMSO), a non-toxic solvent, to prepare casting solutions containing polyvinylidene fluoride and an antifouling random copolymer made of polystyrene and poly(ethylene glycol) methyl ether methacrylate (PS-r-PEGMA). Membranes were formed by vapor-induced phase separation (VIPS). They were shown to be homogeneous in terms of structure and surface chemistry (tested by mapping FT-IR), suggesting compatibility of the polymer/copolymer/solvent system and justifying the choice of DMSO. Membrane hydration was drastically improved after adding PS-r-PEGMA with a water contact angle falling from 140° to 47°. As a result, biofouling by Escherichia coli and whole blood was reduced by > 90% in static conditions. During several filtration cycles of a highly fouling Escherichia coli solution flux recovery ratio could be increased from 16% (pristine membrane) to 29% (PEGylated membrane). All in all, this study reveals that low-biofouling homogeneous porous membranes can be prepared by in-situ modification and the VIPS process using a greener approach than traditionally reported.

2D nanosheets optimized electrospray-assisted interfacial polymerization polyamide membrane with excellent separation performance

Electrospray-assisted interfacial polymerization has recently raised researchers’ attention during membrane fabrication process due to the thickness of the polyamide layer is tunable in nanometers. Here we report that 2D molybdenum disulfide (MoS2) nanosheets could endow the electrospray-assisted interfacial polymerization polyamide membrane with improved selectivity at a short spray time. The nanosheets dispersed uniformly under the electric field. The optimal TFN-15 membrane demonstrated water permeance of 9.23 L m−2 h−1·bar−1 and Na2SO4 rejection of 95.4%. Furthermore, the obtained polyamide membranes showed splendid stability and antifouling. Our research provides an effective strategy for the optimization of the fabrication process of the electrospray-assisted interfacial polymerization polyamide membrane with high-performance.

Optimization of Nanofiltration Hollow Fiber Membrane Fabrication Process Based on Response Surface Method

Layer-by-layer (LBL) self-assembly technology has become a new research hotspot in the fabrication of nanofiltration membranes in recent years. However, there is a lack of a systematic approach for the assessment of influencing factors during the membrane fabrication process. In this study, the process optimization of LBL deposition was performed by a two-step statistical method. The multiple linear regression was performed on the results of single-factor experiments to determine the major influencing factors on membrane performance, including the concentration of Poly (allylamine hydrochloride) (PAH), glutaraldehyde, and the NaCl concentration in PAH solution. The Box–Behnken response surface method was then used to analyze the interactions between the selected factors, while their correlation with the membrane performance was obtained by polynomial fitting. The R2 value of the regression models (0.97 and 0.94) was in good agreement with the adjusted R2 value (0.93 and 0.86), indicating that the quadratic response models were adequate enough to predict the membrane performance. The optimal process parameters were finally determined through dual-response surface analysis to achieve both high membrane permeability of 14.3 LMH·MPa−1 and MgSO4 rejection rate of 90.22%.

Ultrathin 12-nm-thick solvent-resistant composite membranes from biosourced dialdehyde starch and priamine building blocks

Biomass-based thin film composites (TFCs) fabricated only from abundant natural resources are emerging as next-generation organic solvent nanofiltration membranes. However, most of the existing membrane fabrication processes still use toxic chemicals, harsh solvents, and fossil-based supports. We report a plant-based, green TFC membrane based solely on sustainable resources. It is the thinnest defect-free nanofilm (only 12-nm-thick) fabricated only from natural resources. Dialdehyde starch was crosslinked with priamine at the interface of a water–eucalyptol solvent system. Interfacial polymerization occurred on a biodegradable cellulose acetate support obtained using phase inversion. The membrane has an ultrathin (12-nm-thick) selective layer, and the molecular weight cut-off and permeance were fine-tuned between 366 and 624 ​g ​mol−1 and 7 and 23 ​L ​m−2 ​h−1 ​bar−1, respectively. Stable nanofiltration performance under continuous crossflow filtration was achieved for seven days. The sustainability of the membrane fabrication platform was compared with those of other platforms. Our TFC membrane fabrication platform enables the conversion of biomass-based building blocks into high-value-added products.

The Application of Principal Component Analysis (PCA) for the Optimization of the Conditions of Fabrication of Electrospun Nanofibrous Membrane for Desalination and Ion Removal.

Nowadays, acquiring a water supply for urban and industrial uses is one of the greatest challenges facing humanity for ensuring sustainability. Membrane technology has been considered cost-effective, encompasses lower energy requirements, and at the same time, offers acceptable performance. Electrospun nanofibrous membranes (ENMs) are considered a novel and promising strategy for the production of membranes that could be applied in several treatment processes, especially desalination and ion removal. In this study, we apply an unsupervised machine-learning strategy, the so-called principal component analysis (PCA), for the purpose of seeking discrepancies and similarities between different ENMs. The main purpose was to investigate the influence of membrane fabrication conditions, characteristics, and process conditions in order to seek the relevance of the application of different electrospun nanofibrous membranes (ENMs). Membranes were majorly classified into single polymers/layers, from one side, and dual multiple layer ENMs, from another side. For both classes, variables related to membrane fabrication conditions were not separated from membrane characterization variables. This reveals that membranes’ characteristics not only depend on the chemical composition, but also on the fabrication conditions. On the other hand, the process conditions of ENM fabrication showed an extensive effect on membranes’ performance.