Interfacially polymerized thin-film composite membranes: Impact of support layer pore size on active layer polymerization and seawater desalination performance

Dual modification of reverse osmosis membranes with NH2-MIL-125 and functionalised multiwalled carbon nanotubes for enhanced nanoplastic removal

The present study describes a novel double-modified strategy for developing high-performance thin-film composite reverse osmosis (TFC-RO) membranes by incorporating titanium-based metal organic frameworks (NH2-MIL-125) and functionalised multiwalled carbon nanotubes (MWCNTs) into the support layer and selective layer, respectively. Initially, the support layer was subjected to successive modifications using NH2-MIL-125 mixed with polysulfone (PSF) in dimethylformamide DMF solution to investigate their impact on the performance and properties of the support layer and resultant TFC-RO membranes. Results indicated that the new structure of the modified support layer had significant influences on the developed TFC-RO membranes. Notably, the pristine PSF support exhibited a large surface pore size, medium porosity, and strong hydrophobicity, resulting in a low-flux TFC-RO membrane. However, after modification with NH2-MIL-125, the optimal blend support demonstrated a small surface pore size, high porosity, and improved hydrophilicity, favouring the formation of a high performance TFC-RO membrane. The incorporation of functionalised MWCNTs nanochannels into the selective layer, using the optimal NH2-MIL-125-PSF blended support, resulted in a smoother and more hydrophilic TFC-RO membrane with enhanced negative charge to improve antifouling properties against negative foulants (i.e., nanoplastics (NPs) and bovine serum albumin (BSA)). The double-modified membrane (TFC-RO-DM) exhibited superior performance over the conventional PSF-TFC-RO membrane. Notably, the maximum water flux reached 39 L m-2.h-1 with 98.4% NaCl rejection. The membrane exhibited a high flux recovery rate of 92% following a 30-min physical cleaning process. Additionally, the TFC-RO-DM membrane displayed reduced fouling against NPs suggesting the great promise of this innovative double-modification approach for the advancement of high-performance TFC-RO membranes.

Evaluating Post-Treatment Effects on Electrospun Nanofiber as a Support for Polyamide Thin-Film Formation

Poly(acrylonitrile-co-methyl acrylate) (PAN-co-MA) electrospun nanofiber (ENF) was used as the support for the formation of polyamide (PA) thin films. The ENF support layer was post-treated with heat-pressed treatment followed by NaOH hydrolysis to modify its support characteristics. The influence of heat-pressed conditions and NaOH hydrolysis on the support morphology and porosity, thin-film formation, surface chemistry, and membrane performances were investigated. This study revealed that applying heat-pressing followed by hydrolysis significantly enhances the physicochemical properties of the support material and aids in forming a uniform polyamide (PA) thin selective layer. Heat-pressing effectively densifies the support surface and reduces pore size, which is crucial for the even formation of the PA-selective layer. Additionally, the hydrolysis of the support increases its hydrophilicity and decreases pore size, leading to higher sodium chloride (NaCl) rejection rates and improved water permeance. When compared with membranes that underwent only heat-pressing, those treated with both heat-pressing and hydrolysis exhibited superior separation performance, with NaCl rejection rates rising from 83% to 98% while maintaining water permeance. Moreover, water permeance was further increased by 29% through n-hexane-rinsing post-interfacial polymerization. Thus, this simple yet effective combination of heat-pressing and hydrolysis presents a promising approach for developing high-performance thin-film nanocomposite (TFNC) membranes.

Reuse of end-of-life membranes through accelerated polyamide degradation

End-of-life (EoL) thin-film composite (TFC) reverse osmosis membranes were converted into ultrafiltration-like (UF) membranes in an accelerated degradation process of the polyamide (PA) using an oxidant (NaOCl) in the presence of either MgCl2 or CaCl2. The PA degradation was evaluated by measuring pure water permeability (PWP), MgSO4 passage and molecular weight cut-off; the more PWP increased, and the less MgSO4 was retained after treatment, the more the PA was degraded. By adding 10 mM of metal ions, PWP increased 2.1 (MgCl2) and 3.1 (CaCl2) times compared to the increase achieved with hypochlorite alone (2560 ppm∙h of free chlorine). Changes in the membranes after treatment were analyzed by Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), and by measuring their surface charge and contact angle. FTIR and FE-SEM confirmed the PA layer degradation. FE-SEM micrographs showed that full removal of the PA layer can be achieved by using an oxidation dose of 12,700 ppm∙h when Ca2+ is used but doses as high as 300,000 ppm*h are needed without catalyst. The results proved that by controlling the oxidation process it was possible to control the cut-off (MWCO) value of the membrane from 16,100 g∙mol-1 to 27,100 g∙mol-1. Before treatment, EoL membranes showed a MWCO of approximately 1200 g∙mol-1, meaning that molecules with that size could be retained in a 90%. In summary, the presented method enables reducing waste by the conversion EoL membranes into tailored UF-like membranes and by decreasing the amount of oxidant used in the conversion process.

Development of Support Layers and Their Impact on the Performance of Thin Film Composite Membranes (TFC) for Water Treatment

Thin-film composite (TFC) membranes have gained significant attention as an appealing membrane technology due to their reversible fouling and potential cost-effectiveness. Previous studies have predominantly focused on improving the selective layers to enhance membrane performance. However, the importance of improving the support layers has been increasingly recognized. Therefore, in this review, preparation methods for the support layer, including the traditional phase inversion method and the electrospinning (ES) method, as well as the construction methods for the support layer with a polyamide (PA) layer, are analyzed. Furthermore, the effect of the support layers on the performance of the TFC membrane is presented. This review aims to encourage the exploration of suitable support membranes to enhance the performance of TFC membranes and extend their future applications.

A Facile Strategy toward the Preparation of a High-Performance Polyamide TFC Membrane with a CA/PVDF Support Layer

In this study, polyamide (PA) thin-film composite (TFC) nanofiltration membranes were fabricated via interfacial polymerization on cellulose acetate (CA)/poly(vinylidene fluoride) (PVDF) support layers. Several types of CA/PVDF supports were prepared via the phase inversion method. With increasing CA, the PVDF membrane surface pore size decreased and hydrophilicity increased. The effect of the support properties on the performance and formation mechanism of PA films was systematically investigated via an interfacial polymerization (IP) process. The permselectivity of the resulting TFC membranes was evaluated using a MgSO4 solution. The results show that the desired polyamide TFC membrane exhibited excellent water flux (6.56 L/(m2·h·bar)) and bivalent salt ion rejection (>97%). One aim of this study is to explore how the support of CA/PVDF influences the IP process and the performance of PA film.

Optimization of Preparation Conditions of Poly(m-phenylene isophthalamide) PMIA Hollow Fiber Nanofiltration Membranes for Dye/Salt Wastewater Treatment

Externally selective thin film composite (TFC) hollow fiber (HF) nanofiltration membranes (NFMs) hold great industrial application prospects because of their high surface area module. However, the complicated preparation process of the membrane has hindered its mass manufacture and application. In this work, PMIA TFC HF NFMs were successfully prepared by the interfacial polymerization (IP) of piperazine (PIP) with 1,3,5-benzenetricarbonyl trichloride (TMC). The effect of the membrane preparation conditions on their separation performance was systematically investigated. The characterized results showed the successful formation of a polyamide (PA) separation layer on PMIA HF substrates by the IP process. The as-prepared HF NFMs’ performance under optimized conditions achieved the highest pure water permeability (18.20 L·m−2·h−1, 0.35 MPa) and superior salt rejection in the order: RNa2SO4 (98.30%) > RMgSO4 (94.60%) > RMgCl2 (61.48%) > RNaCl (19.24%). In addition, the as-prepared PMIA HF TFC NFMs exhibited desirable pressure resistance at various operating bars and Na2SO4 feed concentrations. Excellent separation performance of chromotrope 2B dye was also achieved. The as-prepared PMIA HF NFMs thus show great promise for printing and dyeing wastewater treatment.

Seawater Reverse Osmosis Performance Decline Caused by Short-Term Elevated Feed Water Temperature

The shortage of fresh water resources has made the desalination of seawater a widely adopted technology. Seawater reverse osmosis (SWRO) is the most commonly used method for desalination. The SWRO process is energy-intensive, and most of the energy in SWRO is spent on pressurizing the seawater to overcome the osmotic barrier for producing fresh water. The pressure needed depends on the salinity of the seawater, its temperature, and the membrane surface properties. Membrane compaction occurs in SWRO due to hydraulic pressure application for long-term operations and operating temperature fluctuations due to seasonal seawater changes. This study investigates the effects of short-term feed water temperature increase on the SWRO process in a full-scale pilot with pretreatment and a SWRO installation consisting of a pressure vessel which contains seven industrial-scale 8" diameter spiral wound membrane elements. A SWRO feed water temperature of 40 °C, even for a short period of 7 days, caused a permanent performance decline illustrated by a strong specific energy consumption increase of 7.5%. This study highlights the need for membrane manufacturer data that account for the water temperature effect on membrane performance over a broad temperature range. There is a need to develop new membranes that are more tolerant to temperature fluctuations.

The Intrinsic Parameters of the Polyamide Nanofilm in Thin-Film Composite Reverse Osmosis (TFC-RO) Membranes: The Impact of Monomer Concentration

The realistic resistance zone of water and salt molecules to transport across a TFC-RO membrane is the topmost polyamide nanofilm. The existence of hollow voids in the fully aromatic polyamide (PA) film gives its surface ridge-and-valley morphologies, which confuses the comprehensions of the definition of the PA thickness. The hollow voids, however, neither participate in salt–water separation nor hinder water penetrating. In this paper, the influence of intrinsic thickness (single wall thickness) of the PA layer on water permeability was studied by adjusting the concentration of reacting monomers. It confirms that the true permeation resistance of water molecules originates from the intrinsic thickness portion of the membrane. The experimental results show that the water permeability constant decreases from 3.15 ± 0.02 to 2.74 ± 0.10 L·m−2·h−1·bar−1 when the intrinsic thickness of the membrane increases by 9 nm. The defects on the film surface generate when the higher concentration of MPD is matched with the relatively low concentration of TMC. In addition, the role of MPD and TMC in the micro-structure of the PA membrane was discussed, which may provide a new way for the preparation of high permeability and high selectivity composite reverse osmosis membranes.

Tailored design of nanofiltration membranes for water treatment based on synthesis-property-performance relationships

Tailored design of high-performance nanofiltration (NF) membranes is desirable because the requirements for membrane performance, particularly ion/salt rejection and selectivity, differ among the various applications of NF technology ranging from drinking water production to resource mining. However, this customization greatly relies on a comprehensive understanding of the influence of membrane fabrication methods and conditions on membrane properties and the relationships between the membrane structural and physicochemical properties and membrane performance. Since the inception of NF, much progress has been made in forming the foundation of tailored design of NF membranes and the underlying governing principles. This progress includes theories regarding NF mass transfer and solute rejection, further exploitation of the classical interfacial polymerization technique, and development of novel materials and membrane fabrication methods. In this critical review, we first summarize the progress made in controllable design of NF membrane properties in recent years from the perspective of optimizing interfacial polymerization techniques and adopting new manufacturing processes and materials. We then discuss the property-performance relationships based on solvent/solute mass transfer theories and mathematical models, and draw conclusions on membrane structural and physicochemical parameter regulation by modifying the fabrication process to improve membrane separation performance. Next, existing and potential applications of these NF membranes in water treatment processes are systematically discussed according to the different separation requirements. Finally, we point out the prospects and challenges of tailored design of NF membranes for water treatment applications. This review bridges the long-existing gaps between the pressing demand for suitable NF membranes from the industrial community and the surge of publications by the scientific community in recent years.

Enhancing H2O2 Tolerance and Separation Performance through the Modification of the Polyamide Layer of a Thin-Film Composite Nanofiltration Membrane by Using Graphene Oxide

Through interfacial polymerization (IP), a polyamide (PA) layer was synthesized on the top of a commercialized polysulfone substrate to form a thin-film composite (TFC) nanofiltration membrane. Graphene oxide (GO) was dosed during the IP process to modify the NF membrane, termed TFC-GO, to enhance oxidant resistance and membrane performance. TFC-GO exhibited increased surface hydrophilicity, water permeability, salt rejection, removal efficiency of pharmaceutical and personal care products (PPCPs), and H₂O₂ resistance compared with TFC. When H₂O₂ exposure was 0–96,000 ppm-h, the surfaces of the TFC and TFC-GO membranes were damaged, and swelling was observed using scanning electron microscopy. However, the permeate flux of TFC-GO remained stable, with significantly higher NaCl, MgSO₄, and PPCP rejection with increasing H₂O₂ exposure intensity than TFC, which exhibited a 3.5-fold flux increase with an approximate 50% decrease in salt and PPCP rejection. GO incorporated into a PA layer could react with oxidants to mitigate membrane surface damage and increase the negative charge on the membrane surface, resulting in the enhancement of the electrostatic repulsion of negatively charged PPCPs. This hypothesis was confirmed by the significant decrease in PPCP adsorption onto the surface of TFC-GO compared with TFC. Therefore, TFC-GO membranes exhibited superior water permeability, salt rejection, and PPCP rejection and satisfactory resistance to H₂O₂, indicating its great potential for practical applications.

Influence of monomers involved in the fabrication of a novel PES based nanofiltration thin-film composite membrane and its performance in the treatment of common effluent (CETP) textile industrial wastewater

OBJECTIVE

In this article, monomers (tannic acid (TA) and m- phenylenediamine (MPD)) were used in the fabrication of a novel PES based thin-film composite nanofiltration (TFC-NF) membrane for the treatment of a common effluent treatment plant (CETP) of textile industrial wastewater.

MEMBRANE SYNTHESIS

PES support sheets and TFC layers were fabricated via non-solvent induced phase inversion and in-situ interfacial polymerization (IP) process. The ultra-thin active layer was synthesized via the IP process with monomers such as tannic acid (TA) and m- phenylenediamine (MPD). T and M series membranes correspond to (PES/x wt% TA, x = 2, 4, 6) as T1, T2, T3 -TA and (PES/x wt% MPD, x = 2, 4, 6) as M1, M2, M3-MPD respectively. M0 corresponds to PES which is the virgin membrane.

RESULTS

The chemical structure, surface morphology, surface roughness and surface properties were explored using fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM) and contact angle, respectively. The filtration performance of the thin-film composite nanofiltration (TFC-NF) membranes was investigated by various properties like pure water flux, salt rejection, porosity, mean pore radius and antifouling analysis.

CONCLUSION

T1-TA membrane showed better water permeability, high salt rejection and better industrial effluent rejection with 94.4% of TDS that are suitable for industrial reuse and agricultural irrigation. Moreover, for T1-TA membrane, the water flux, porosity, mean pore radius, salt rejection, surface roughness and contact angle of 43.5lm^- 2 h ^- 1, 47.1%, 16.7nm, 72.7%, 11.7nm and 41.48°was achieved respectively that was found to be higher than that of all the other fabricated membranes. Further, the rejection efficiency rate of textile effluent characteristics such as pH, turbidity, TDS, alkalinity, total hardness, BOD and COD were also achieved with maximum deduction in the T1-TA TFC-NF membrane compared to the M0-Virgin PES membrane. From the results, it can be confirmed that the T1-TA membrane significantly reduced the alkalinity, total hardness, BOD and COD rejections of 78%, 77.3%, 58.5% and 67.5% respectively, present in the effluent. Water flux recovery ratio (FRR) was improved from 74.6% for M0-Virgin PES membrane to 94.8% for T1-TA membrane. The modified TFC-NF membranes especially T1-TA, had better anti-fouling property and excellent hydrophilicity than the unmodified M0-Virgin PES membrane.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40201-021-00624-x.

Preparation and Characterization of Polyphenylsulfone (PPSU) Membranes for Biogas Upgrading

Asymmetric polyphenylsulfone (PPSU) membranes were fabricated by a non-solvent induced phase inversion method. Glycerin and silica nanoparticles were added into the polymer solution to investigate their effects on the material properties and gas separation performance of prepared membranes. The morphology and structure of PPSU membranes were analyzed by scanning electron microscopy (SEM), the surface roughness of the selective layer was analyzed by atomic force microscopy (AFM), and the surface free energy was calculated based on the contact angle measurements by using various solvents. The gas separation performance of PPSU membranes was estimated by measuring the permeability of CO₂ and CH₄. The addition of glycerin as a nonsolvent into the polymer solution changed the cross-section structure from finger-like structure into sponge-like structure due to the delayed liquid-liquid demixing process, which was confirmed by SEM analysis. The incorporation of silica nanoparticles into PPSU membranes slightly increased the hydrophilicity, which was confirmed by water contact angle results. PPSU membrane fabricated from the polymer solution containing 10 wt.% glycerin showed the best CO₂/CH₄ selectivity of 3.86 and the CO₂ permeability of 1044.01 Barrer. Mixed matrix PPSU membrane containing 0.1 wt.% silica nanoparticles showed the CO₂/CH₄ selectivity of 3.16 and the CO₂ permeability of 1202.77 Barrer.

A Review on Reverse Osmosis and Nanofiltration Membranes for Water Purification

Sustainable and affordable supply of clean, safe, and adequate water is one of the most challenging issues facing the world. Membrane separation technology is one of the most cost-effective and widely applied technologies for water purification. Polymeric membranes such as cellulose-based (CA) membranes and thin-film composite (TFC) membranes have dominated the industry since 1980. Although further development of polymeric membranes for better performance is laborious, the research findings and sustained progress in inorganic membrane development have grown fast and solve some remaining problems. In addition to conventional ceramic metal oxide membranes, membranes prepared by graphene oxide (GO), carbon nanotubes (CNTs), and mixed matrix materials (MMMs) have attracted enormous attention due to their desirable properties such as tunable pore structure, excellent chemical, mechanical, and thermal tolerance, good salt rejection and/or high water permeability. This review provides insight into synthesis approaches and structural properties of recent reverse osmosis (RO) and nanofiltration (NF) membranes which are used to retain dissolved species such as heavy metals, electrolytes, and inorganic salts in various aqueous solutions. A specific focus has been placed on introducing and comparing water purification performance of different classes of polymeric and ceramic membranes in related water treatment industries. Furthermore, the development challenges and research opportunities of organic and inorganic membranes are discussed and the further perspectives are analyzed.

Preparation of Polymer Membranes by In Situ Interfacial Polymerization

Membranes currently have a wide application in sewage treatment and water purification processes, in seawater desalination, and in various technological processes where high product purity is required. Deposition of an ultrathin skin layer of TFC (thin-film composite) and TFN (thin-film nanocomposite) onto the surface of membranes is discussed in this article. Their presence improves membrane properties such as retention of impurities and permeability. The aim of this paper is to present the current state of knowledge about the methods of preparing composite and nanocomposite membranes. The properties of the prepared TFC membranes can be modified by changing the type and concentration of the reacting monomers, and the physical conditions in which the membrane preparation process itself is carried out are also significant. Additionally, the properties of TFN membranes can be further modified with nanocomposites. The membranes are characterized by different properties not only because they have nanoparticles in their structure but also because their concentration and the way they are blended into the membrane structure were changed. This paper provides information on modifications of TFN membranes with nanoparticles, as well as modification by changes in polymerization reaction conditions and monomer concentration. Examples of the use of TFN and TFC membranes are also presented.

A review: the effect of the microporous support during interfacial polymerization on the morphology and performances of a thin film composite membrane for liquid purification

The thin film composite (TFC) membrane prepared by interfacial polymerization (IP) on porous supports is currently one of the most efficient technologies for brackish water purification and seawater desalination, including reverse osmosis (RO), forward osmosis (FO), and nanofiltration (NF). Over the past decades, there have been intensive and continuous efforts in research of polyamide layers, while there is little information in the literature about the impact that physical–chemical properties and structure of support membranes have on the formation of composite membranes. This paper reviews the recent research progress of the supporting membrane, comprehensively summarizes the support role in polyamide formation, and provides good insight into TFC membrane research and development. In addition, we discuss several types of polymer supporting membranes and related modification methods to explore the appropriate supporting membrane for enhancing TFC membrane performance and extending the applications in the future.

The thin film composite membrane prepared by interfacial polymerization on porous supports is currently one of the most efficient technologies for brackish water purification and seawater desalination, including reverse osmosis, forward osmosis and nanofiltration.