Polyethersulfone Ultrafiltration Membranes Research Articles

Visible-light-activated Fe2O3–TiO2 nanoparticles enhance biofouling resistance of polyethersulfone ultrafiltration membranes against marine algae Chlorella vulgaris

This study investigated the modification of polyethersulfone (PES) ultrafiltration membranes with TiO2 and Fe2O3–TiO2 nanoparticles to enhance their hydrophilicity and biofouling resistance against the marine microalgae Chlorella vulgaris. It is a common freshwater and marine microalga that readily forms biofilms on membrane surfaces, leading to significant flux decline and increased operational costs in ultrafiltration processes. The microalgae cells and their extracellular polymeric substances (EPS) adhere to the membrane surface, creating a dense fouling layer that impedes water permeation. The modified membranes were characterized using contact angle measurements, scanning electron microscopy, and pure water flux/resistance tests. Short-term ultrafiltration experiments evaluated the membranes’ antifouling performance by measuring flux decline, flux recovery ratio, and relative flux reduction during C. vulgaris filtration. The TiO2 membrane showed improved hydrophilicity and antifouling over the pristine PES membrane, while the Fe2O3–TiO2 nanocomposite membrane exhibited the best performance. It reduced the water contact angle and showed only a 5% relative flux reduction compared to 60% for the pristine membrane. SEM images confirmed reduced microalgal deposition on the nanocomposite surface. Long-term tests with microalgal cells under dark and visible light conditions in saline water further assessed the membranes’ biofouling resistance. The Fe2O3–TiO2 membrane maintained 59 L/m2 h water flux under visible light after immersion in the microalgal solution, outperforming the pristine (38 L/m2 h) and TiO2 (52 L/m2 h) membranes. This superior antifouling was attributed to photocatalytic generation of reactive oxygen species inhibiting microalgal adhesion. This study demonstrates a promising strategy for mitigating biofouling in membrane-based water treatment and desalination processes.

Preparation of TA-O-MoS2/PES mixed matrix ultrafiltration membrane for rare earth wastewater treatment

The trade-off between permeability and selectivity, along with the issue of membrane fouling, has constrained the widespread application of ultrafiltration (UF) membranes in recycling rare earth wastewater. Here, we present the incorporation of tannic acid (TA) modified molybdenum disulfide oxide (O-MoS2) as a functional enhancer to fabricate polyethersulfone (PES) based mixed matrix membranes through a nonsolvent induced phase separation (NIPS) approach. Compared to the unmodified PES membrane, the integration of TA-O-MoS2 significantly improves the hydrophilicity, porosity in the mixed matrix membrane. By altering the concentration of TA-O-MoS2, the TA-O-MoS2/PES UF membrane achieves enhanced hydrophilicity and charge properties, resulting in a remarkable improvement in separation performance. Specifically, the optimized membrane M2 (TA-O-MoS2 addition of 0.1 wt%) exhibits a water flux of 140.98 Lm−2h−1bar−1 and a PEG 20000 rejection rate of 91.00 %, representing increases of 180 % and 120 % over the control PES membrane, respectively. Notably, membrane M2 effectively retains 91.31 % of macromolecular organic compounds in rare earth wastewater, while permitting nearly complete passage of inorganic salts, for instance CaCl2 (3.26 %) and MgSO4 (4.84 %). Moreover, the TA-O-MoS2/PES membrane demonstrates robust antifouling properties and exceptional durability, indicating its significant potential for efficient treatment and resource recovery in rare earth wastewater.

Direct-through channels of ZIF-8 composite membranes via in-situ PolyBMA sealing: Radical-induced phase transformation and dye removal efficiency

Metal-organic frameworks (MOFs)-based hybrid composite membranes are promising candidates for achieving highly efficient water purification. In this study, a facile, novel pressure-induced filtration method involving in-situ polymerization of butyl methacrylate (BMA) was proposed for sealing ZIF-8 nanoparticles on top of polyethersulfone (PES) ultrafiltration membrane support. The developed (ZIF-8+polyBMA)/PES composite membranes with thin toplayers of <1 μm present attractive water permeance (up to 31 LMH/bar) and good rejection of Congo red (99.2 %) and Methylene blue (99.1 %). The ZIF-8 particles served as direct-through channels with superior separation performance due to their high porosity and tunable pore structure, while the interstices were successfully sealed with polyBMA by in-situ polymerization, as demonstrated by SEM and dye removal experiments. It was found that the morphology of ZIF-8 transformed from a rhombic dodecahedron to two-dimensional hexagonal nanosheets during the fabrication process. We hypothesize that this surprising phenomenon is caused by the reaction of the initiators (Na2S2O5 and K2S2O8) that generate the hydroxyl and sulfate radicals attacking and transforming the Zn-MIM bond network of ZIF-8. However, insights into the structural changes need to be further investigated to understand the mechanism involved.

Analysis of a constant-volume diafiltration system with the ability to remove lithium cations when using poly(2-acrylamido-2-methyl-1-propanesulfonic acid) in water

This study describes the synthesis of a poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS) and its application for the removal of Li+ in water using a constant-volume diafiltration system. PAMPS with molecular weights exceeding 100 kDa (88 % w/w), polymerisation yields of 97 % and high acidity was obtained. A block experimental design characterized the diafiltration system reporting: Regenerated cellulose (RC) and polyethersulfone (PES) ultrafiltration membranes with a molecular cut-off of 100 kDa can retain up to 1 % Li+ ions through surface charges. But when PAMPS 2000 kDa was used, 89 % of Li+ was removed (%R). Permeate flux (Js) decreases with increasing PAMPS:Li+ ratio, whereas the %R value increases. The filtration process is controlled by diffusion mechanisms according to the Peclet dimensionless number. Using PAMPS 100 kDa with a PAMPS:Li+ ratio (20:1), %R decreases to 76 %, whereas Js increases slightly. PAMPS can be reused 3 consecutive times, maintaining a Li+ cation rejection efficiency of >60 %. Additionally, it was found that the percentage of Li+ rejection capacity exercised with PAMPS is reduced to 60 % when Ca2+, K+, Mg2+ and Na+ cations are present.

Dopamine hydrochloride and L-arginine Co-functionalized halloysite nanotubes for modification of polyethersulfone ultrafiltration membrane with improved separation performance

In recent years, a range of high-performance ultrafiltration membranes have been developed, but maintaining high retention without sacrificing high throughput remains a serious challenge. In this paper, functionalized halloysite nanotubes is constructed by copolymerization and by a one-step reaction of L-arginine and dopamine hydrochloride using halloysite nanotubes as carriers. Subsequently, modified polyethersulfone membranes are prepared by blending them as additives through non-solvent-induced phase transition separation. As the synthesized nanofillers is rich in functional groups, negative electronegativity, and unique structures, the study focuses on adding nanofillers’ effect on the membrane structure and physicochemical properties. The addition of appropriate nanofillers enhances the membrane surface wettability and negative electronegativity, and the enlarged internal pores and the dense layer that remains flat and homogeneous effectively promote the flux of small molecules, the retention of large molecules, and the cyclic stability of the membrane. The prepared polyethersulfone membranes demonstrate exceptional cycle stability, high separation efficiency (almost 100 % for Congo red), and significantly improved permeation performance (initial permeate flux up to 316.5 L m-2h−1). The results demonstrate the high potential of the modified prepared polyethersulfone membranes for pertinent environmental separation processes.

Charge mediated nano-filtration for recovering sinapic acid from a mustard bran hydrolysate

The recovery of valuable chemicals, such as sinapic acid, from enzymatic hydrolysates is essential to enabling a sustainable biorefinery. In this study, we designed a system to recover sinapic acid produced chemo-enzymatically from waste mustard bran. The process involves sequential separation, beginning with size partitioning using ultrafiltration for enzyme removal and recovery, followed by charge-mediated size partitioning via nanofiltration to isolate sinapic acid from other extracts. Four polyethersulfone (PES) ultrafiltration membranes with molecular weight cut-offs (MWCOs) of 5000 and 10 000 Da and maximum allowable working pressures (MAWPs) of 3 and 10 bar were screened for their effectiveness in removing Bovine Serum Albumin (BSA) as a model compound. Subsequently, these membranes were applied to recover the feruloyl esterase enzyme. The membrane with an MWCO of 5000 Da and an MAWP of 10 bar achieved 97.93 % enzyme recovery with a permeate flow rate of 31.4 L/h/m2 at 6 bar. Next, we evaluated the effects of zeta potential interactions on the preferential rejection of sinapic acid using various nanofiltration membranes with potentially charged surfaces, including polyimide, silicon-based thin film composite, and polypiperazine amide membranes with MWCOs ranging from 150 to 600 Da. The polypiperazine amide membrane demonstrated the highest recovery of sinapic acid, achieving 86 % recovery from a model solution and 64 % recovery from mustard bran hydrolysate. Compositional analysis of the permeate confirmed that the rejection rate (R) is influenced primarily by the pKa rather than molecular size, following the trend: sinapic acid (pKa = 4.58; 224.2 Da; R = 64.0 %), acetic acid (pKa = 4.76; 60.1 Da; R = 23.8 %), xylose (pKa = 12.15; 150.1 Da; R = 13.7 %), glucose (pKa = 12.28; 180.2 Da; R = 8.7 %), and arabinose (pKa = 12.34; 150.1 Da; R = 8.5 %). The zeta potential interactions across nanofiltration membranes enhanced sinapic acid recovery from the mustard bran hydrolysate, hence, charge mediation significantly influenced the membrane separation of these complex mixtures with varying pKa values.

Polyethersulfone ultrafiltration membranes co‐blended with amphiphilic polymers and nitrogen‐doped titanium dioxide nanoparticles for anti‐fouling and photocatalysis

Polyethersulfone ultrafiltration membranes co‐blended with amphiphilic polymers and nitrogen‐doped titanium dioxide nanoparticles for anti‐fouling and photocatalysis

The effect of activated carbon nanoparticles (ACNPs) on characterization and mechanical properties of polyethersulfone (PES) ultrafiltration membranes

The effect of activated carbon nanoparticles (ACNPs) on characterization and mechanical properties of polyethersulfone (PES) ultrafiltration membranes

Adsorption of steroid hormone micropollutant by polyethersulfone ultrafiltration membranes with varying morphology

The effective removal of micropollutants necessitates the use of dense membranes, such as thin-film composite (TFC) reverse osmosis (RO) and nanofiltration (NF) membranes. TFCs have a polyamide active layer interfacially polymerized on a support layer that is typically made of polysulfone (PSu) or polyethersulfone (PES). Retention by NF and RO is often incomplete because micropollutants are adsorbed to the polymer material and subsequently permeate via a combination of convection and diffusion, which evidences a breakthrough curve. When describing breakthrough phenomena, the role of the support membrane is commonly neglected, even though the adsorption in this layer can be significant. This work investigated the adsorption of steroid hormone micropollutants (17β-estradiol, E2) by fabricated and commercial PES ultrafiltration membranes with varying morphology.By increasing the coagulation bath temperature between 10 and 70 °C, the pure water permeability increased from 13 to 3800 L/m2·h−1·bar−1, and consequently, the average pore size rose from 12 to 191 nm. The fabricated membranes with smaller pore sizes showed higher E2 removal via adsorption which can be attributed to the higher internal surface area. The adsorbed mass of fabricated PES membranes (using dimethylformamide (coded as PDG) and N-methyl-2-pyrrolidone (coded as PNG) and PES (Istanbul Technical University (ITU), with non-woven supports) varies from 0.30 to 0.60, 0.27–0.60 and 1–1.2 ng·cm−2, respectively. These values are lower than the adsorbed masses with commercial Biomax (Millipore Inc.) membranes (0.5–2.0 ng·cm−2). Ultrafiltration membranes used as support for composite membranes, nanofiltration or as filters in sample preparation benefit from lower micropollutant adsorption.

Polyethersulfone mixed matrix membrane with abundant sponge pores for high‐separation performance with high flux retention and cycling stability

AbstractIn recent years, a series of high‐performance ultrafiltration membranes have been developed, but maintaining high flux and high pollutant retention rate without sacrificing service life remains a long‐standing challenge. In this study, a porous polyethersulfone ultrafiltration membrane enriched with ZIF‐8 and TiO2 additives is prepared based on a non‐solvent induced phase separation method. During the phase transition process, the addition of organic nanocrystals ZIF‐8 and inorganic nanocrystals TiO2 delayed the phase transition rate, resulting in the transformation of the polyethersulfone modified membrane from a finger‐like pore structure to a sponge‐like pore structure. Compared to other structures, the sponge‐like modified membrane has a uniform and narrow pore size distribution, fewer surface defects, stable retention performance, and can simultaneously improve membrane permeability and mechanical strength. Therefore, the polyethersulfone modified membrane with a sponge‐like pore structure prepared in this research exhibits high flux for small molecules and good retention rate for large molecules. Long‐term cycling stability tests of the modified membrane shows high retention rate (over 98%), high flux, long service life, and good cycling stability for solute molecules. The study indicates that the prepared polyethersulfone modified membrane has high potential for application in relevant environmental separation processes.

Development of zwitterion-functionalized graphene oxide/polyethersulfone nanocomposite membrane and fouling evaluation using solutes of varying charges

Abstract This study explores the functionalization of polyethersulfone (PES) ultrafiltration (UF) membranes using zwitterion-functionalized graphene oxide (GO) and assesses their interactions with solutes of different charges, both neutral and anionic. Initially, PES nanocomposite membranes were synthesized, incorporating varying dosages (ranging from 0-1 % (w/w)) of glycine-functionalized graphene oxide (Gly/GO) and diglycine-functionalized graphene oxide (diGly/GO) through a direct blending method. The physicochemical properties, including hydrophilicity, surface morphology, and porosity of these membranes were characterized using sessile-drop contact angle, tabletop scanning electron microscopy (SEM), and gravimetric methods, respectively. Subsequently, the antifouling performance of these synthesized membranes was assessed by exposing them to a solution containing sucrose as a neutral model foulant and humic acid as an anionic foulant. The incorporation of zwitterion-functionalized graphene oxide nanoparticles improved the surface wettability of the nanocomposite membrane, enhancing its resistance to sucrose fouling. This was supported by a reduction in flux declination ratio (e.g., 40.6 % for pristine PES, 29.7 % for 1.0 % (w/w) Gly/GO PES, and 33.1 % for 1.0 % (w/w) diGly/GO PES) and an increase in flux recovery ratio (67.2 % for pristine PES, 79.7 % for 1.0 % (w/w) Gly/GO PES, and 80.0% for 1.0 % (w/w) diGly/GO PES). The improvement in antifouling characteristics is attributed to the formation of a hydration layer on the membrane surface, which inhibits sucrose deposition. However, zwitterion-functionalized PES nanocomposite membranes displayed a higher affinity for anionic humic acid, resulting in a substantial flux decline and a lower flux recovery ratio. Overall, this research provides insights into the roles of surface wettability and the charge interactions between solutes and the membrane surface, both of which are crucial factors in determining fouling severity and the restorability of spent membranes.

Performance of Chitosan/Carbon Nanotube-Coated Ultrafiltration Membranes for Natural Organic Matter Removal from Drinking Water

The objective of this study is to improve the filtration efficiency of commercially available polyethersulfone (PES) ultrafiltration (UF) membranes, with a specific focus on removing natural organic matter (NOM) and preventing membrane fouling. The modification of UF membranes was accomplished by utilizing chitosan/multi-walled carbon nanotubes (CS/MWCNT-OH) and employing both dip and spin coating techniques. The membrane surface morphologies were evaluated using the Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), and Energy-Dispersive X-ray Spectroscopy (EDX) techniques. Tests were carried out to assess the effectiveness of the membranes in a laboratory-scale system using two primary water sources from Istanbul, specifically the Melen River and Terkos Lake. Total organic carbon (TOC), UV254 absorbance, turbidity, and trihalomethane formation potential (THMFP) were all measured as part of a thorough analysis. The surface morphology investigations verified the effective deposition of MWCNT-OH nanoparticles onto the membrane surface. This was corroborated by the reduction in the water contact angle, showing an improvement in the hydrophilicity of the membrane. The modified membranes demonstrated much higher TOC removal rates compared to the original membranes. Specifically, the removal efficiencies for Melen River and Terkos Lake were 37.14% and 56.86%, respectively. Nevertheless, the alteration of the surface led to a decline in membrane flux as a result of the concurrent drop in pore size. To summarize, the results of this work highlights the considerable capability of surface modification using CS/MWCNT-OH to improve the performance and antifouling characteristics of commercial PES UF membranes.

Analysis the Effect of Flux and Water Characteristics on Polyethersulfone Ultrafiltration Membrane Performance as Pre-Treatment of SWRO

Increasing human population resulted in higher demand for potable freshwater, while freshwater sources were limited. As an alternative solution, seawater was necessarily to be employed as a main source of water supply and necessarily treated with Seawater Reverse Osmosis (SWRO). However, membrane fouling of SWRO was occurred. Therefore, implementation of ultrafiltration membranes as pre-treatment were necessary. In this study, identification of removal efficiency seawater characteristics of TDS, COD, conductivity, and UV-Vis parameters at different flux and investigation of the fouling rate at variations filtration performance of the 50 kDa MWCO pore size PES ultrafiltration membrane was performed. Filtration of laboratory scale experiment with constant flux of 120 L/m²⋅h and 180 L/m²⋅h at dead-end operation was performed. Filtration of 50 kDa PES ultrafiltration membrane was able to remove effectively turbidity, TDS, UV-Vis, conductivity, and COD with 63±6%; 37±19%; 7±4%; 33±33%; dan 97.86%, respectively. Furthermore, related to membrane performance, filtration at 120 L/m²·h flux operation was found as the common fouling mechanisms, while flux operation at 180 L/m²·h resulted different behavior resulted for severe membrane performance. The suitable operation of fluxes 120 L/m²·h was recommended to increase the performance and membrane lifespan as well as to decrease the load of SWRO unit.

Effects of Alkaline Cleaning Agents on the Long-Term Performance and Aging of Polyethersulfone Ultrafiltration Membranes Applied for Treatment of Car Wash Wastewater.

The commercial ultrafiltration polyethersulfone (PES) membranes (10 and 100 kDa) blended with polyvinylpyrrolidone (PVP) were applied for the filtration of car wash wastewater. Periodical membrane rinsing with water did not prevent fouling and a decrease in permeate flux was observed. Fouling was reduced by washing the membranes with cleaning agents, which are used in car washes to clean wheels and remove insects. In addition to surfactants, these agents contain NaOH, hence the pH value of cleaning solutions was over 11. Long-term contact with such solutions resulted in the removal of PVP from the membrane matrix and an increase in pore size. The PES membranes were soaked in an alkaline solution (pH = 11.5) for 20 months, after which the 200 kDa dextran rejection decreased from 95% to 80%. To compare with the static degradation conditions, 8 weeks of alkaline agent filtration was realized, after which the dextran (200 kDa) rejection decreased below 50%. This indicated that the cross-flow of alkaline agents can accelerate the removal of components building the membrane matrix. Despite membrane degradation, the separation efficiency (the rejection of chemical oxygen demand-COD, turbidity, and surfactants) during the treatment of synthetic car wash wastewater was similar to that obtained for pristine membranes.

A novel polyethersulfone ultrafiltration membrane with enhanced permeability and antifouling ability via melamine-modified metal-organic framework

The trade-off between permeability and selectivity, as well as membrane fouling remains a major challenge in membrane application, impacting the performance and lifespan. Herein, a novel approach has been proposed, involving the incorporation of melamine-modified Metal-Organic Frameworks (MOFs) into Polyethersulfone (PES) ultrafiltration membranes. The modified MOFs exhibit stable anchoring to the membrane surface through hydrogen bonding, forming a hydration layer that enhances resistance to foulants. Moreover, the MOF framework channels facilitate water transport via providing additional pathways. The optimized melamine-MOF modified membranes achieve a permeability of 50 L/m2.h and a 97.8 % bovine serum albumin (BSA) rejection. The antifouling experiment demonstrates an 87 % fouling recovery ratio (FRR) for the modified membrane. A computational study has been conducted to investigate the interaction between UiO-66 and melamine using molecular dynamics (MD) simulations. The simulations validated the formation of hydrogen bonds and confirmed previous findings. Overall, the melamine-modified MOF exhibits high permeability and antifouling ability due to its excellent hydrophilic properties, which offer promising application prospects in wastewater reclamation.

Ta-Fe in-situ coating PES membrane and its application in oily wastewater treatment: Insight into modification and anti-fouling mechanisms

Membrane fouling is a serious problem that limits the widespread application of membrane technology. Herein, we propose an effective modification method by in-situ modifying polyethersulfone (PES) ultrafiltration membrane with tannic acid (TA) and Fe3+ chelates to improve its pollution resistance. The TA-Fe3+ complexes could deposit on the PES membrane surface and form a hydration layer by Van Der Waals force, hydrogen bonding force, and hydrophobic association. The modified membrane (PES\\TA\\Fe3+) had enhanced fouling resistance and membrane flux due to its dual advantages of abundant OH groups and favorable spatial structure. After modification, the roughness of membrane surface increased from 219 nm to 257 nm, and its water contact angle decreased from 58.9° to 26.5°, endowing the PES\\TA\\Fe3+ membrane with a strong resistance to oil droplets through electrostatic repulsion, steric hindrance effect, and hydrogen bonding force. Polyaluminum chloride-polydimethyldiallylammonium chloride (PAC-PDMDAAC) could alleviate 85 % membrane fouling resistance. PAC-PDMDAAC mainly mitigated irreversible membrane fouling by removing oil droplets and forming large and loose flocs. While the use of PES\\TA\\Fe3+ membrane mainly reduced the adsorption resistance and the resistance of membrane itself. The anti-fouling performance of PES\\TA\\Fe3+ membrane changed with pH owing to the changes in the properties of TA-Fe3+ complexes. The hydrophilic layer would be decomposed under alkaline conditions due to the deprotonation of TA and excessive hydrolysis of Fe3+. This study provides an efficient anti-fouling strategy and reveals the modification and anti-fouling mechanisms of the hydrophilic membrane, providing theoretical guidance for the further development of membrane technology.

Enhanced properties of a positive-charged nanofiltration membrane containing quaternarized chitosan through second interfacial polymerization for the removal of salts and pharmaceuticals.

Nanofiltration (NF) membrane technology has been widely used in the removal of salts and trace organic pollutants, such as pharmaceuticals and personal care products (PPCPs), due to its superiority. A positive-charged composite NF membrane with an active skin layer was prepared by polyethyleneimine (PEI), trimethyl benzene chloride, and quaternate chitosan (HTCC) through second interfacial polymerization on the polyethersulfone ultrafiltration membrane. The physicochemical properties of the nanocomposite membrane were investigated using surface morphology, hydrophilicity, surface charge, and molecular weight cut-off (MWCO). The influence of the concentration and reaction time of PEI and HTCC was documented. The optimized membrane had a MWCO of about 481 Da and possessed a pure water permeability of 25.37 L·m-2·h-1·MPa-1. The results also exhibited salt rejection ability as MgCl2 > CaCl2 > MgSO4 > Na2SO4 > NaCl > KCl, showing a positive charge on the fabricated membrane. In addition, the membrane had higher rejection to atenolol, carbamazepine, amlodipine, and ibuprofen at 89.46, 86.02, 90.12, and 77.21%, respectively. Moreover, the anti-fouling performance and stability of the NF membrane were also improved.

Enhanced antifouling and separation capabilities of polydopamine@Ce-MOF functionalized PES ultrafiltration membrane

The need for antifouling membranes is substantial due to fouling’s negative impact on the effectiveness and durability of ultrafiltration membranes. In recent times, Metal-Organic Frameworks (MOFs) have emerged as effective additives for crafting ultrafiltration (UF) membranes. However, to harness their benefits and mitigate their drawbacks, a well-considered approach is imperative. In this work, polyethersulfone (PES) UF membranes were tailored with polydopamine (PDA)-modified cerium (Ce)-MOF (PDA@Ce-MOF) to achieve satisfactory antifouling properties and to remove biological macromolecules such as bovine serum albumin (BSA) and humic acid (HA) from wastewater. The non-solvent induced phase separation (NIPS) method was used to simultaneously fabricate the membrane and modify it with different PDA@Ce-MOF concentrations ranging from 0.05 to 0.50 wt.%. Results showed significant improvements on the membrane’s morphology, hydrophilicity, porosity and pore size at 0.10 wt.% loading of PDA@Ce-MOF. The synergistic effect of the PDA and Ce-MOF on the membrane improved the pure water flux (337 L m−2 h−1) and filtration performance in the filtration of Bovine serum albumin (BSA) and humic acid (HA) reporting 145 L m−2 h−1 and 98% rejection, and 164 L m−2 h−1 and 88% rejection; respectively. Further, water-attracting functional moieties of PDA@Ce-MOF hindered the deposition of BSA protein on the membrane surface, resulting in an excellent flux recovery ratio (FRR) of ~87%, alongside mitigated irreversible fouling.

Flux decline in crossflow ultrafiltration-based diafiltration process for lignin recovery from a deep eutectic solvent comprised of lactic acid and choline chloride

This study investigates a continuous ultrafiltration (UF)-based diafiltration (DF) method to separate and purify lignin from a deep eutectic solvent (DES) containing lactic acid and choline chloride after biomass delignification. A crossflow setup with a polyether sulfone UF membrane with a molecular weight cut off of 5000 Da was used to evaluate flux decline and fouling in this process. Under different pressure, feed flowrate, lignin, and DES concentrations, lignin rejection is around 0.90. Higher lignin and DES concentrations increase filtration resistance, and thus decrease flux at constant pressure. On the basis of a previously setup model based on dead-end filtration, a modeling approach was further developed to predict the system size required to implement UF-DF on a large scale. The results shows that at a constant pressure, the membrane system's area increases as the cake layer thickness over the membrane's surface increases.

Tannin-assisted interfacial polymerization towards COF membranes for efficient dye separation.

Membrane separation has been shown to have significant potential in addressing the global shortage of clean water. Covalent organic frameworks (COFs) have gained significant attention in the field of membrane separation due to their structural stability and controllable pore size. Here, a modification of polyethersulfone ultrafiltration membranes with TA-assisted COFs is prepared by interfacial polymerization and co-deposition. Intriguingly, in comparison to the conventional COF synthesis method, the interfacial polymerization reaction used n-butanol as the oil-phase monomer to prevent substrate corrosion. More importantly, the TA-assisted co-deposition not only introduces a large number of environmentally friendly hydrophilic groups to enhance the hydrophilicity of the membrane surface, but also the phenolic hydroxyl group contained in TA generates a quinone group upon oxidation. This group can undergo a Michael addition reaction with the amine group, followed by interfacial polymerization to regulate the COFs pore size. Consequently, the optimized membrane exhibited a high permeation flux of 122.03 L m-2 h-1 bar-1 without altering the pore size structure of the original membranes and demonstrated separation performance for various dyes (Mw: 300-1300 g mol-1), with a retention rate of over 98%. Despite multiple filtrations of methyl blue dye, the membrane prepared by simple rinsing still exhibited high retention rates (>98%) with exceptional stability and retention performance. The optimized membrane demonstrated good hydrophilicity and dye separation performance, indicated promising potential for dye separation applications.