Separation of proteins and antifouling properties of polyphenylsulfone based mixed matrix hollow fiber membranes

Performance Investigation of PSF-nAC Composite Ultrafiltration Membrane for Protein Separation

As a promising wastewater treatment technology, ultrafiltration membranes face challenges related to fouling and flux reduction. To enhance these membranes, various strategies have been explored. Among them, the incorporation of nano-activated carbon (nAC) powder has emerged as an effective method. In this study, composite polysulfone (PSF) ultrafiltration membranes were fabricated using nAC powder at concentrations ranging from 0 to 8 wt.%. These membranes underwent comprehensive investigation, including assessments of membrane morphology, hydrophilicity, pure water flux, equilibrium water content, porosity, average pore size, and protein separation. The addition of activated carbon improved several desirable properties. Specifically, the hydrophilicity of the PSF membranes was enhanced, with the contact angle reduced from 69° to 58° for 8 wt.% of nAC composite membranes compared to the pristine PSF membrane. Furthermore, the water flux test revealed that 6 wt.% activated carbon-based membranes exhibited the highest flux, with a nearly 3 times improvement at 2 bar. Importantly, this enhancement did not compromise the protein rejection. Additionally, the introduction of nAC had a significant effect on the membrane's pore size by improving lysozyme rejection up to 40%. Overall, these findings will guide the selection of the optimal concentration of nAC for PSF ultrafiltration membranes.

Influence of PEG-PPG-PEG Block Copolymer Concentration and Coagulation Bath Temperature on the Structure Formation of Polyphenylsulfone Membranes

The effect of amphiphilic block copolymer polyethylene glycol (PEG)-polypropylene glycol (PPG)-PEG concentration in the polyphenylsulfone (PPSU) casting solution and coagulation bath temperature (CBT) on the structure, separation, and antifouling performance of PPSU ultrafiltration membranes was studied for the first time. According to the phase diagram obtained, PPSU/PEG-PPG-PEG/N-methyl-2-pyrrolidone (NMP) systems are characterized by a narrow miscibility gap. It was found that 20 wt.% PPSU solutions in NMP with the addition of 5-15 wt.% of PEG-PPG-PEG block copolymer feature upper critical solution temperature, gel point, and lower critical solution temperature. Membrane composition and structure were studied by Fourier-transform infrared spectroscopy, scanning electron and atomic force microscopies, and water contact angle measurements. The addition of PEG-PPG-PPG to the PPSU casting solution was found to increase the hydrophilicity of the membrane surface (water contact angle decreased from 78° for the reference PPSU membrane down to 50° for 20 wt.%PPSU/15 wt.% PEG-PPG-PEG membrane). It was revealed that the pure water flux increased with the rise of CBT from 18-20 L·m-2·h-1 for the reference PPSU membrane up to 38-140 L·m-2·h-1 for 20 wt.% PPSU/10-15 wt.% PEG-PPG-PEG membranes. However, the opposite trend was observed for 20 wt.% PPSU/5-7 wt.% PEG-PPG-PEG membranes: pure water flux decreased with an increase in CBT. This is due to the differences in the mechanism of phase separation (non-solvent-induced phase separation (NIPS) or a combination of NIPS and temperature-induced phase separation (TIPS)). It was shown that 20 wt.% PPSU/10 wt.% PEG-PPG-PEG membranes were characterized by significantly higher antifouling performance (FRR-81-89%, DRr-26-32%, DRir-10-20%, DT-33-45%) during the ultrafiltration of bovine serum albumin solutions compared to the reference PPSU membrane prepared at different CBTs (FRR-29-38%, DRr-6-14%, DRir-74-89%, DT-88-94%).

Scale Design of Dual-Layer Polyphenylsulfone/Sulfonated Polyphenylsulfone Hollow Fiber Membranes for Nanofiltration

This study focuses on the synthesis and characterization of dual-layer sulfonated polyphenylenesulfone (SPPSu) nanocomposite hollow fiber nanofiltration membranes incorporating titanium dioxide (TiO2) nanoparticles through the phase inversion technique. Advanced tools and methods were employed to systematically evaluate the properties and performance of the newly developed membranes. The investigation primarily centered on the impact of TiO2 addition in the SPPSu inner layer on pure water permeability and salt rejection. The nanocomposite membranes exhibited a remarkable three-fold increase in pure water permeability, achieving a flux of 5.4 L/m2h.bar compared to pristine membranes. The addition of TiO2 also enhanced the mechanical properties, with an expected tensile strength increase from 2.4 to 3.9 MPa. An evaluation of salt rejection performance using a laboratory-scale filtration setup revealed a maximal rejection of 95% for Mg2SO4, indicating the effective separation capabilities of the modified dual-layer hollow fiber nanocomposite membranes for divalent ions. The successful synthesis and characterization of these membranes highlight their potential for nanofiltration processes, specifically in selectively separating divalent ions from aqueous solutions, owing to their improved pure water flux, mechanical strength, and salt rejection performance.

In Situ Incorporation of TiO2@Graphene Oxide (GO) Nanosheets in Polyacrylonitrile (PAN)-Based Membranes Matrix for Ultrafast Protein Separation

Organic polymeric ultrafiltration (UF) membranes have been widely used in protein separation due to their advantages of high flux and simple manufacturing process. However, due to the hydrophobic nature of the polymer, pure polymeric UF membranes need to be modified or hybrid to increase their flux and anti-fouling performance. In this work, tetrabutyl titanate (TBT) and graphene oxide (GO) were simultaneously added to the polyacrylonitrile (PAN) casting solution to prepare a TiO₂@GO/PAN hybrid ultrafiltration membrane using a non-solvent induced phase separation (NIPS). During the phase separation process, TBT underwent a sol-gel reaction to generate hydrophilic TiO₂ nanoparticles in situ. Some of the generated TiO₂ nanoparticles reacted with the GO through a chelation interaction to form TiO₂@GO nanocomposites. The resulting TiO₂@GO nanocomposites had higher hydrophilicity than the GO. They could selectively segregate towards the membrane surface and pore walls through the solvent and non-solvent exchange during the NIPS, significantly improving the membrane's hydrophilicity. The remaining TiO₂ nanoparticles were segregated from the membrane matrix to increase the membrane's porosity. Furthermore, the interaction between the GO and TiO₂ also restricted the excessive segregation of the TiO₂ nanoparticles and reduced their losing. The resulting TiO₂@GO/PAN membrane had a water flux of 1487.6 L·m^-2·h^-1 and a bovine serum albumin (BSA) rejection rate of 99.5%, which were much higher than those of the currently available UF membranes. It also exhibited excellent anti-protein fouling performance. Therefore, the prepared TiO₂@GO/PAN membrane has important practical applications in the field of protein separation.

Recent advances in development of functional magnetic adsorbents for selective separation of proteins/peptides

Nowadays, proteins separation has attracted great attention in proteomics research. Because the proteins separation is helpful for making an early diagnosis of many diseases. Magnetic nanoparticles are an interesting and useful functional material, and have attracted extensive research interest during the past decades. Because of the excellent properties such as easy surface functionalization, tunable biocompatibility, high saturation magnetization etc, magnetic microspheres have been widely used in isolation of proteins/peptides. Notably, with the rapid development of surface decoration strategies, more and more functional magnetic adsorbents have been designed and fabricated to meet the growing demands of biological separation. In this review, we have collected recent information about magnetic adsorbents applications in selective separation of proteins/peptides. Furthermore, we present a comprehensive prospects and challenges in the field of protein separation relying on magnetic nanoparticles.

Preparation and Characterization of Modified Polysulfone with Crosslinked Chitosan-Glutaraldehyde MWCNT Nanofiltration Membranes, and Evaluation of Their Capability for Salt Rejection

Nanofiltration membranes were successfully created using multi-walled carbon nanotubes (MWCNTs) and MWCNTs modified with amine (MWCNT-NH2) and carboxylic groups (MWCNT-COOH). Chitosan (CHIT) and chitosan−glutaraldehyde (CHIT-G) were utilized as dispersants. Sonication, SEM, and contact angle were used to characterize the as-prepared membranes. The results revealed that the type of multi-walled carbon nanotubes (MWCNT, MWCNT-COOH and MWCNT-NH2) used as the top layer had a significant impact on membrane characteristics. The lowest contact angle was 38.6 ± 8.5 for the chitosan-G/MWCNT-COOH membrane. The surface morphology of membranes changed when carbon with carboxylic or amine groups was introduced. In addition, water permeability was greater for CHIT-G/MWCNT-COOH and CHIT-G/MWCNT-NH2 membranes. The CHIT-G/MWCNT-COOH membrane had the highest water permeability (5.64 ± 0.27 L m−2 h−1 bar−1). The findings also revealed that for all membranes, the rejection of inorganic salts was in the order R(NaCl) > R(MgSO4).

Effect of Composition and Viscosity of Spinning Solution on Ultrafiltration Properties of Polyphenylene Sulfone Hollow-Fiber Membranes

In this work, PPSUs with different molecular weights were synthesized for the development of highly permeable ultrafiltration hollow fiber membranes for the first time. The MW of the synthesized polymers was controlled by varying the monomers molar ratio within 1:1-1.15 under the same synthesis conditions. Based on the study of the rheological properties of polymer solutions, a high molecular weight PPSU (MW 102,000 g/mol) was chosen for the formation of hollow fiber membranes. The addition of PEG400 to the spinning solution led to an increase in viscosity, which makes it possible to work in the region of lower PPSU concentrations (18-20 wt. %) and to form membranes with a less dense porous structure. With the addition of PEG400 to the spinning solution, the membrane permeance increased sharply by more than two orders of magnitude (from 0.2 to 96 L/m2 h bar). At the same time, the membranes had high rejection coefficients (99.9%) of Blue Dextran model filtered substance (MW = 69,000 g/mol).

Development of High Flux Nanocomposite Polyphenylsulfone/Oxidized Multiwalled Carbon Nanotubes Membranes for Ultrafiltration Using the Systems with Critical Solution Temperatures

The study deals with the investigation of the effect of the modification of polyphenylsulfone (PPSU) flat sheet membranes for ultrafiltration using oxidized multiwalled carbon nanotubes (O-MWCNT) in order to enhance membrane permeability and antifouling performance. The effect of O-MWCNT loading to the PPSU-polyethylene glycol (PEG-20,000, M_n = 20,000 g·mol⁻¹)-polyvinylpyrrolidone (PVP K-30, M_n = 40,000 g·mol⁻¹)-N-methy-2-pyrrolidinone (NMP) colloid systems on the phase state and viscosity was studied. It was found that PPSU-PEG-20,000-PVP K-30-O-MWCNT-NMP colloid systems feature a gel point (T = 35–37 °C) and demixing temperature (T = 127–129 °C) at which two bulk phases are formed and a polymer system delaminates. According to the study of the phase state and viscosity of these colloid systems, a method for the preparation of high flux PPSU membranes is proposed which includes processing of the casting solution at the temperature higher than gel point (40 °C) and using a coagulation bath temperature lower than gel point (25 °C) or lower than demixing temperature (40 °C and 70 °C). Membrane structure, topology and hydrophilic-hydrophobic balance were investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and water contact angle measurements. The effect of coagulation bath temperature and O-MWCNT concentration on the membrane separation and antifouling performance in ultrafiltration of human serum albumin and humic acids solutions was studied. It was found that the modification of PPSU ultrafiltration membranes by O-MWCNTs yielded the formation of a thinner selective layer and hydrophilization of the membrane surface (water contact angle decreased from 53–56° for the reference PPSU membrane down to 33° for the nanocomposite membrane with the addition of 0.19 wt.% O-MWCNT). These changes resulted in the increase in membrane flux (from 203–605 L·m⁻²·h⁻¹ at transmembrane pressure of 0.1 MPa for the reference membrane up to 512–983 L·m⁻²·h⁻¹ for nanocomposite membrane with the addition of 0.19 wt.% O-MWCNT depending on coagulation bath temperature) which significantly surpasses the performance of PPSU ultrafiltration membranes reported to date while maintaining a high level of human serum albumin rejection (83–92%). It was revealed that nanocomposite membrane demonstrated better antifouling performance (the flux recovery ratio increased from 47% for the reference PPSU membrane up to 62% for the nanocomposite membrane) and higher total organic carbon removal compared to the reference PPSU membrane in humic acids solution ultrafiltration.

Recent Advancements in Polyphenylsulfone Membrane Modification Methods for Separation Applications

Polyphenylsulfone (PPSU) membranes are of fundamental importance for many applications such as water treatment, gas separation, energy, electronics, and biomedicine, due to their low cost, controlled crystallinity, chemical, thermal, and mechanical stability. Numerous research studies have shown that modifying surface properties of PPSU membranes influences their stability and functionality. Therefore, the modification of the PPSU membrane surface is a pressing issue for both research and industrial communities. In this review, various surface modification methods and processes along with their mechanisms and performance are considered starting from 2002. There are three main approaches to the modification of PPSU membranes. The first one is bulk modifications, and it includes functional groups inclusion via sulfonation, amination, and chloromethylation. The second is blending with polymer (for instance, blending nanomaterials and biopolymers). Finally, the third one deals with physical and chemical surface modifications. Obviously, each method has its own limitations and advantages that are outlined below. Generally speaking, modified PPSU membranes demonstrate improved physical and chemical properties and enhanced performance. The advancements in PPSU modification have opened the door for the advance of membrane technology and multiple prospective applications.

Recent Advances in Biopolymeric Membranes towards the Removal of Emerging Organic Pollutants from Water

Herein, this paper details a comprehensive review on the biopolymeric membrane applications in micropollutants' removal from wastewater. As such, the implications of utilising non-biodegradable membrane materials are outlined. In comparison, considerations on the concept of utilising nanostructured biodegradable polymeric membranes are also outlined. Such biodegradable polymers under considerations include biopolymers-derived cellulose and carrageenan. The advantages of these biopolymer materials include renewability, biocompatibility, biodegradability, and cost-effectiveness when compared to non-biodegradable polymers. The modifications of the biopolymeric membranes were also deliberated in detail. This included the utilisation of cellulose as matrix support for nanomaterials. Furthermore, attention towards the recent advances on using nanofillers towards the stabilisation and enhancement of biopolymeric membrane performances towards organic contaminants removal. It was noted that most of the biopolymeric membrane applications focused on organic dyes (methyl blue, Congo red, azo dyes), crude oil, hexane, and pharmaceutical chemicals such as tetracycline. However, more studies should be dedicated towards emerging pollutants such as micropollutants. The biopolymeric membrane performances such as rejection capabilities, fouling resistance, and water permeability properties were also outlined.

Effect of Polyphenylsulfone and Polysulfone Incompatibility on the Structure and Performance of Blend Membranes for Ultrafiltration

This study deals with the modification of polyphenylsulfone ultrafiltration membranes by introduction of an incompatible polymer polysulfone to the polyphenylsulfone casting solution to improve the permeability. The correlation between properties of the blend polyphenylsulfone/polysulfone solutions and porous anisotropic membranes for ultrafiltration prepared from these solutions was revealed. The blend polyphenylsulfone/polysulfone solutions were investigated using a turbidity spectrum method, optical microscopy and measurements of dynamic viscosity and turbidity. The structure of the prepared blend flat sheet membranes was studied using scanning electron microscopy. Membrane separation performance was investigated in the process of ultrafiltration of human serum albumin buffered solutions. It was found that with the introduction of polysulfone to the polyphenylsulfone casting solution in N-methyl-2-pyrrolidone the size of supramolecular particles significantly increases with the maximum at (40–60):(60:40) polyphenylsulfone:polysulfone blend ratio from 76 nm to 196–354 nm. It was shown that polyphenylsulfone/polysulfone blend solutions, unlike the solutions of pristine polymers, are two-phase systems (emulsions) with the maximum droplet size and highest degree of polydispersity at polyphenylsulfone/polysulfone blend ratios (30–60):(70–40). Pure water flux of the blend membranes passes through a maximum in the region of the most heterogeneous structure of the casting solution, which is associated with the imposition of a polymer-polymer phase separation on the non-solvent induced phase separation upon membrane preparation. The application of polyphenylsulfone/polysulfone blends as membrane-forming polymers and polyethylene glycol (M_n = 400 g·mol⁻¹) as a pore-forming agent to the casting solutions yields the formation of ultrafiltration membranes with high membrane pure water flux (270 L·m⁻²·h⁻¹ at 0.1MPa) and human serum albumin rejection of 85%.

Polyphenylsulfone (PPSU)-Based Copolymeric Membranes: Effects of Chemical Structure and Content on Gas Permeation and Separation

Although various polymer membrane materials have been applied to gas separation, there is a trade-off relationship between permeability and selectivity, limiting their wider applications. In this paper, the relationship between the gas permeation behavior of polyphenylsulfone(PPSU)-based materials and their chemical structure for gas separation has been systematically investigated. A PPSU homopolymer and three kinds of 3,3',5,5'-tetramethyl-4,4'-biphenol (TMBP)-based polyphenylsulfone (TMPPSf) copolymers were synthesized by controlling the TMBP content. As the TMPPSf content increases, the inter-molecular chain distance (or d-spacing value) increases. Data from positron annihilation life-time spectroscopy (PALS) indicate the copolymer with a higher TMPPSf content has a larger fractional free volume (FFV). The logarithm of their O₂, N₂, CO₂, and CH₄ permeability was found to increase linearly with an increase in TMPPSf content but decrease linearly with increasing 1/FFV. The enhanced permeability results from the increases in both sorption coefficient and gas diffusivity of copolymers. Interestingly, the gas permeability increases while the selectivity stays stable due to the presence of methyl groups in TMPPSf, which not only increases the free volume but also rigidifies the polymer chains. This study may provide a new strategy to break the trade-off law and increase the permeability of polymer materials largely.

Nano CuO/g-C3N4 sheets-based ultrafiltration membrane with enhanced interfacial affinity, antifouling and protein separation performances for water treatment application

To improve the interfacial affinity and antifouling properties of polyphenylsulfone (PPSU) membrane, nano CuO/g-C₃N₄ (g-CN) sheets were synthesized via facile calcination route as one pot synthesis method. The uniformly assembled nanohybrid fillers, CuO on g-CN sheets were confirmed by using XRD, TEM, EDX and FTIR analysis. The non-solvent induced phase inversion technique was used to fabricate the nanohybrid ultrafiltration (UF) membranes by doping different concentration (0.5-1 wt.%) of nano CuO/g-C₃N₄ (g-CN) sheets within the PPSU matrix. The results of contact angle, atomic force microscopy, energy-dispersive X-ray spectroscopy reveal that surface structure and physico-chemical properties of nanohybrid membrane plays lead role in solute interaction and rejection compared to bare membrane, M0. Furthermore, the interfacial affinity of membrane was explored in detail via surface free energy, spreading coefficient, wetting tension and reversible work of adhesion analysis. Nanohybrid UF membrane, with 0.5% of the filler (M1) displayed remarkable permeation flux of 202, 131 L/m²/hr for pure water and protein solution, respectively while maintaining a high protein rejection (96%). Moreover, the exceptional dispersion of the nanosheets in the polymer matrix enhanced FRR (79%) and decreased the overall resistance of M1 compared to the pristine membrane (M0). Overall results suggest that the incorporation of nano sheets is a facile modification technique which improves the comprehensive membrane performance and holds a great potential to be further explored for water treatment.