Abstract In this study, L-histidine zwitterionic carbon dots (HZCDs) were synthesized using the hydrothermal method. The synthesized HZCDs were used to modify polyethersulfone (PES) membranes. Additionally, the HZCDs-modified membranes were activated using the protease enzyme to prepare protease-activated composite membranes. The prepared materials underwent extensive characterization and validation using various techniques, including Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR), and X-ray Diffraction (XRD) analyses. The blending or activation of HZCDs by the protease enzyme reduced the contact angle of the prepared membranes. The contact angle decreased from 78.75° to 50.12° and 40.02° for 2.0 wt.% HZCDs-PES and PES/Protease-HZCDs membranes, respectively. As the contact angle decreased, the hydrophilic nature of the prepared membranes increased, reflecting a strong affinity for water and efficient wettability. In this context, the pure water flux (PWF) values of PES membranes increased from 140.5 ± 5.3 to 248.7 ± 8.4 L/m 2 .h with rising HZCDs amount from 0 to 2 wt.% HZCDs-PES. Additionally, PWF values for protease-activated composite membranes increased from 140.5 ± 5.3 to 321.1 ± 9.2 L/m 2 . h. BSA flux values of PES membranes increased from 56.4 ± 2.4 to 82.9 ± 0.9 L/m 2 .h with increasing HZCDs amount from 0 to 2.0 wt.% HZCDs-PES. Besides, BSA values for protease-activated composite membranes increased from 56.4 ± 2.4 to 89.8 ± 2.2 L/m 2 .h. The purpose of this modification was to impart hydrophilic properties to the PES membrane and address the issue of membrane fouling, which is a common problem in filtration processes. 2.0 wt.% HZCDs-PES and enzyme-activated membranes PES membranes demonstrated 100% BSA removal efficiency. Also, 2.0 wt.% HZCDs-blended membranes and 2.0 wt.% protease-HZCDs-blended membranes demonstrated remarkable antifouling properties up to 87.7% and 88.8% flux recovery ratio (FRR), respectively. In contrast, BSA flux recovery reached only 67.8% for the pristine PES. When compared to pristine PES membranes, enzyme-activated membranes demonstrated superior filtration and protein rejection efficiencies.

Ultrafiltration membranes are widely used in wastewater filtration due to their efficiency relative to conventional water treatment technologies. To improve the antifouling property of the PVDF membrane, a composite ultrafiltration membrane was fabricated employing the in-situ embedment approach throughout the phase inversion process and utilizing a new 2D material, MAX phase Molybdenum Titanium Aluminium Carbide (Mo2TiAlC2). The membranes were described using Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), and porosity measurements. Rejection tests were applied to study the produced membranes. Adding Mo2TiAlC2 increased the hydrophilicity of the composite membrane compared to the pristine membrane. Porosity and membrane pore size increased with the addition up to 0.6% wt. The most hydrophilic membrane (M3) recorded the highest protein rejection of 84.9%, which was much higher than that of the pristine membrane. These findings highlight the potential of Mo2TiAlC2 as a promising PVDF membrane additive.

A novel chloromethylation (CM) approach was developed to graft the macroinitiator -CH2Cl onto aromatic backbone-bearing polymer materials such as polysulfone (PSf) in the aqueous phase, followed by atomic transfer radical polymerization (ATRP) of zwitterionic polysulfobetaine methacrylate (PSBMA) for antifouling modification. This CM reaction was completed in one step using a mixture of paraformaldehyde, hydrochloric acid, and a phase transfer catalyst (PTC), i.e., 3-(pyridinium-1-yl) propane-1-sulfonate inner salt. Advantages of the described method include: (1) No environmentally hazardous catalysts, such as SnCl4 and ZnCl2, were used. (2) The PTC was chemically stable and recyclable, which was superior to the water-sensitive, almost nonrecyclable Lewis acid. (3) The CM reaction occurred in the presence of hydrochloric acid rather than water-sensitive solvents (e.g., chloroform, sulfuric acid) used in the bulk modification method. Membranes were characterized by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) to verify the presence of -CH2Cl and PSBMA on the surfaces. Under the optimized CM and ATRP conditions, the obtained polysulfone membranes showed a water contact angle (WCA) as low as 25°, their pure water flux (PWF) and protein rejection were simultaneously enhanced, and the flux recovery ratio improved from 72.6% to 92.6%.

Polyethersulfone membranes modified with 2D MXene-CuO nanocomposites for protein rejection and investigation of antimicrobial properties

Metabolic products comparison in autotrophic and heterotrophic nitrogen removal: Insights into membrane fouling.

Poly(acrylonitrile-butadiene-styrene) (ABS) is a common polymer used in toys, automobile parts, and membranes. Membranes fabricated with this copolymer commonly employ toxic solvents and have a dense architecture, which may not work in all applications. This work investigates the synthesis of ABS membranes, using green solvents and the influence of additives on the phase inversion process during the non-solvent-induced phase separation. The addition of water-soluble additives, ethanol, and acetone is hypothesized to provide additional control over viscosity and volatility, and, consequently, impact the phase inversion process. Membranes were fabricated with PolarClean and with various additive concentrations and evaporation times. The resulting membranes were characterized using scanning electron microscopy (SEM) and a pycnometer to visualize the pore structure and obtain porosity information. Membrane performance, including water flux and bovine serum albumin rejection, was evaluated using dead-end cell filtration. Membranes fabricated using only PolarClean had fingerlike pore morphology and relatively low protein rejection. The addition of additives resulted in a change in pore architecture and rejection, which is hypothesized to be a result of additives' volatility, humidity, and destabilization of liquid-liquid separation. This study provides a more detailed understanding of the impact of additives on the resulting ABS membrane structure and performance, with a focus on safer solvents.

This study investigated the use of ultrafiltration for sustainable protein recovery and the treatment of shrimp washing wastewater (SWW). Three ultrafiltration membranes with molecular weight cut-offs of 5, 10, and 50 kDa were tested using a combined ultrafiltration-diafiltration process (UF-DF). The performance of each membrane was assessed based on protein recovery efficiency, chemical oxygen demand (COD) reduction, turbidity, fouling behavior, and cleaning efficiency. The 5 kDa membrane showed superior performance, achieving over 90% protein and COD rejection and producing the highest protein-enriched retentate. It also exhibited the lowest fouling index and best cleaning recovery, confirming its suitability for protein concentration and wastewater treatment. This research highlights UF-DF as a promising, eco-efficient technology for valorizing seafood processing effluents by recovering high-value proteins and reducing environmental discharge loads.

In seeking alternatives for reducing environmental damage, fabricating filtration membranes using biopolymers derived from agro-industrial residues, such as cellulose acetate (CA), partially dissolved with green solvents, represents an economical and sustainable option. However, dissolving CA in green solvents through mechanical agitation can take up to 48 h. An ultrasonic probe was proposed to accelerate mass transfer and polymer dissolution via pulsed interval cavitation. Additionally, ultrasound-assisted phase inversion (UAPI) on the external coagulation bath was assessed to determine its influence on the properties of flat sheet and hollow fiber membranes during phase inversion. Results indicated that the ultrasonic pulses reduced dissolution time by up to 98% without affecting viscosity (3.24 ± 0.06 Pa·s), thermal stability, or the rheological behavior of the polymeric blend. UAPI increased water permeability in flat sheet membranes by 26% while maintaining whey protein rejection above 90%. For hollow fiber membranes, UAPI (wavelength amplitude of 0 to 20%) improved permeability by 15.7% and reduced protein retention from 90% to 70%, with MWCO between 68 and 240 kDa. This report demonstrates the effectiveness of ultrasonic probes for decreasing the dissolution time of dope solution with green cosolvents and its potential to change the structure of polymeric membranes by ultrasound-assisted phase inversion.

Scalable and cost-effective ultra-dispersible graphene oxide blended ultrafiltration mixed matrix membrane: Assessment of mechanical, water flux, and anti-biofouling properties

Innovative membrane engineering: Polyphenylsulfone/silver-doped zinc oxide for high-efficiency protein rejection

Nanofiltration (NF) separation technology is a low-pressure filtration process, which is highly efficient and environmentally friendly. As a result, it has found wide application in water treatment. This work describes the preparation of flat sheet membranes via the phase inversion method using blends of hyperbranched polyester amide (PEA) and polyether sulphone (PES) in definite ratios. The obtained mixed matrix membranes were characterized using FTIR, TGA and contact angle analysis, and their morphologies were investigated using SEM. SEM images showed a porous membrane with micro-voids found underneath, confirming the suitability of the membranes for nanofiltration. Adding PEA to PES changed the porosity, which changed the membrane performance. Examining the removal of heavy metals [Pb(NO3) and CuSO4] using the prepared membranes revealed that the NF membranes had a higher salt rejection efficiency than pure PES with a good permeate flux. M3 membrane showed 81% rejection of Pb (NO3)2, while M2, the membrane with a low PEA ratio, rejected 85%, with high water flux for both membranes. Moreover, the presence of PEA in the membrane tissue led to protein rejection up to 99.5%. Thus, these novel blend membranes proved themselves as NF-type membranes with better performance in water treatment.

The seek for sustainable protein sources has led to the exploration of microalgae as an alternative. Membrane filtration, known for its environmental friendliness, holds promise for purifying protein from microalgae. This research focuses on the protein purification from Chlorella vulgaris microalgae using polyethersulfone (PES) membrane. This research aims to investigate the effect of membrane composition for enhanced microalgae harvesting and protein purification, as well as evaluating the effects of membrane pore sizes and porosity on the performance. Three membrane compositions were evaluated, which are 18% PES, 15% PES, and 12% PES. The membranes were tested for efficiency in microalgae harvesting and protein filtration through dead-end filtration. SEM analysis, contact angle analysis, and theoretical calculations were used to assess membrane characteristics. In terms of algae harvesting, both 18% PES and 15% PES were better than 12% PES in terms of retention of algae. Lowest protein rejection or high protein recovery in the permeate was achieved using 18% PES while 12% PES gave the highest rejection or low protein recovery. Our result can provide valuable guidance for optimizing PES membrane compositions to enhance microalgae-based processes.

Cellulose Acetate (CA) was blended with Polyvinylpyrrolidone (PVP) to produce mixed matrix membranes. Diffusion induced phase separation technique was implemented for the synthesis of CA/PVP protein filtration membrane. The morphology, water permeation efficiencies and bovine serum albumin (BSA) rejection were studied to examine the influence of incorporating PVP in CA membranes. FTIR, contact angle and SEM were used to find out the surface morphology of membrane samples. SEM confirmed homogenous and significant mixing of PVP contents into pure CA matrix. Performance of blended membranes was measured in terms of water permeation and protein rejection percentage. The remarkable lessening of contact angle from 83° to 69° well illustrated the better hydrophilicity of CA/PVP membranes. All CA/PVP membranes rejected >90%. The hydrophilicity, water permeation and protein rejection % of CA membrane were improved by incorporation of 1% by weight PVP (M-1).

Mechanism of shear-enhanced rotating-disk microfiltration for separation of microbe/protein bio-suspension

The superiorities provided by polymeric composite membranes in comparison to the original membrane have generated increased attention, particularly in the field of protein separation applications. This work involved the fabrication of polysulfone composite membranes using variable loadings of activated carbon particle sizes, namely, 37 µm, 74 µm, 149 µm, and 297 µm. The membranes were fabricated via the phase-inversion method, employing water as the coagulant. In this study, the impact of the AC powder particle sizes on membrane morphology, water contact angle, porosity, average pore size, molecular weight cutoff, pure water flux, and protein rejection was examined. Different membrane morphologies and properties were achieved by incorporating a variety of AC particle sizes. A porous membrane with the maximum pure water flux was generated by the loading of finer AC particles. Concurrently, protein rejection is increasing as a result of the use of AC particles as an infill in the composite membrane. In comparison to all fabricated membranes, the AC filler with a particle size of 149 µm exhibited the highest rejection of the lysozyme protein, reaching up to 73.9%, with a relatively high water permeability of 33 LMH/Bar. In conclusion, this investigation provides recommendations for the selection of AC particle sizes for protein separation in conjunction with PSF ultrafiltration membranes.

Abstract This study investigated the fabrication of polyacrylonitrile (PAN) membranes using non‐solvent induced phase separation methods, with the addition of thermoplastic polyurethane (TPU) as an additive. The incorporation of TPU and the utilization of stepwise induced phase separation techniques resulted in notable improvements in membrane structure and water filtration performance. Scanning electron microscopy revealed that membranes with TPU exhibited a denser pore network and finer primary channels, leading to enhanced water flux and protein rejection rates. Mechanical testing indicated that TPU addition improved the membrane's mechanical properties, particularly its elongation at break and tensile strength, especially under wet conditions. Additionally, optimization of the coagulation bath involved methanol spraying followed by water immersion, resulting in membranes with further enhanced flux and rejection properties. Compared with neat PAN membranes, the membranes with TPU exhibited increased water flux from 405 to 539 L/m2 h, as well as improved elongation at break and tensile strength in both dry and wet conditions. Furthermore, the combination of stepwise induced phase separation significantly enhanced the water flux from 342.7 to 483.0 L/m2 h, while also improving the retention rate of ovalbumin from 25.7% to 31.5%.

This study investigates the synthesis of flat sheet asymmetric Polysulfone (PSF) membranes using the Non-Solvent Induced Phase Separation (NIPS) method, enhanced by incorporating Deep Eutectic Solvents (DES) composed of Choline Chloride (ChCl) and DL-Malic Acid (MA). The research explores the individual and combined effects of ChCl and MA on membrane morphology and performance. Comprehensive characterization techniques, including Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy-Universal Attenuated Total Reflectance (FTIR-UATR), and Atomic Force Microscopy (AFM), were employed to analyze the structural and surface properties of the membranes. Key performance metrics such as Pure Water Permeability (PWP), protein and dye rejection, fouling behavior, porosity, surface hydrophilicity, and mechanical strength were evaluated. Results demonstrated that integrating DES into the PSF matrix significantly improved membrane properties. The 3% DES membrane exhibited the highest Pure Water Permeability (PWP) of 186.82 L/m2h/bar, the lowest water contact angle of 68.8°, and optimal balance in surface roughness parameters, leading to superior antifouling properties with high flux recovery ratio (FRR) and balanced reversible (Rr) and irreversible fouling (Rir) components. The ChCl (HBA) membrane displayed a notable PWP of 121.62 L/m2h/bar, large pore sizes (42.72 nm), and moderate surface roughness (Ra of 3.32 nm). In contrast, the MA (HBD) membrane demonstrated the highest hydrophilicity with the lowest contact angle (70.7°) and a compact, robust structure, despite its smallest pore sizes and lack of permeability. The findings underscore the synergistic effect of DES formation in the membrane, improving overall performance for ultrafiltration applications. This study provides valuable insights into the distinct roles of ChCl as an HBA and MA as an HBD in DES-modified PSF membranes, revealing their individual contributions and the importance of optimizing DES components and concentrations for specific filtration applications.

Optimized ceramic membrane-based method for efficient and acid-free rice protein preparation from alkaline extracts

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.

This research explored the use of a partially cross-linked graft copolymer (PCLNPG) as an innovative nanopolymer pore-forming agent to enhance polyphenylsulfone (PPSU) membranes for protein separation applications. The study systematically examined the impact of incorporating PCLNPG at varying concentrations on the morphological and surface properties of PPSU membranes. A thorough characterization of the resulting PPSU-PCLNPG membranes was performed, focusing on changes in morphology, water affinity, porosity, pore size, and pore size distribution. The experimental findings demonstrated that the use of PCLNPG led to a significantly more porous structure, as confirmed by SEM analysis, with notable increases in porosity and pore size (nearly double). Additionally, the hydrophilicity of the PPSU membrane was remarkably enhanced. Performance evaluations revealed a substantial improvement in pure water flux, with the flux nearly tripling. The BSA retention was directly correlated with the concentration of the PCLNPG pore former for a loading range of 0.25–0.75 wt.%. The incorporation of PCLNPG also reduced the membrane fouling propensity by reducing both cake layer resistance (Rc) and pore plugging resistance (Rp). These results underscore the potential of PCLNPG-PPSU membranes for wastewater reclamation and nutrient recovery applications.