Membrane Flux Research Articles

Analysis of membrane fouling during microfiltration of copper sulfide precipitates

Membrane filtration, particularly MF-UF, has previously been assessed as an attractive process for clarifying and recovering valuable metals from metal sulfide precipitation. Previous results of the high transmembrane flux achieved have shown to be promising. However, those studies were primarily focused on demonstrating the method’s feasibility and estimating its performance under different operational conditions. Based on that, this study represents a significant advancement in the field, assessing the fouling behavior and its impact on process performance during the microfiltration of metal sulfide precipitates. Different operational conditions were evaluated using commercial microfiltration membranes operating in batch and continuous regimes, varying Cu concentration in the feed solution (200 and 1800 mg/L), and cross-flow velocities (0.2 – 0.16 m/s). Batch recirculation tests had over 80 % better flux results than the long-term continuous-mode operation tests, mainly due to a progressive decline in the membrane flux observed at longer operation times.Moreover, the cross-flow velocity evaluation indicated that elevated tangential flow rates might result in a decline in the performance of particles with high aggregation behavior. Analyses with modified Hermia’s models and with SEM-EDX image characterizations demonstrated that cake filtration represents the primary fouling mechanism in this process under long-term operation. The present study offers crucial insights that will inform the further development of MF for the treatment of metal sulfide precipitates.

Flake size-dependent water transport through graphene oxide membranes and rejection of geosmin (GSM) and 2-methylisoborneol (MIB) from drinking water

Water transport through graphene oxide membranes (GOMs) and the rejection of inorganic and organic solutes have been extensively studied. However, the influence of the lateral size of GO flakes on membrane performance remains unclear. Here, we investigate the water permeation and separation performance of GOMs fabricated using various sizes of flakes. The membranes prepared with larger flakes showed higher water flux. Our experiment clearly shows that GOMs consist of both lamellae and void structures. Monte Carlo simulations indicate that water transport through the voids is faster than that through the lamellae in GO membranes. Moreover, the voids are more predominant for the membranes prepared with larger sizes of GO flakes and, hence, higher water flux for larger flake membranes. Additionally, the GOMs prepared with the large flakes effectively rejected more than 98 % of geosmin (GSM) and 2-methylisoborneol (MIB) with high reproducibility and a stable water flux of 1.49 LMH. Our results contribute to a better understanding of the complex structure of GOMs, where the rejection performance of membranes mainly depends on the interlayer space, but the water transport is governed by the voids. Our study also demonstrated the industrial potential of GOMs in drinking water purification technology.

Dual synergies of functionalized hydrophilic MOFs based poly (aryl ether ketone sulfone) ultrafiltration membranes: Electrostatic action and pore size screening

In this paper, amino monomer (4Am-PH) and the sulfonated poly (arylene ether ketone sulfone) involving amino groups (Am-SPAEKS) were successfully prepared by diazotization reaction and direct polycondensation, respectively. The polyethyleneimine-modified UiO-66-NH2 (P-MOFs) were prepared as fillers. Composite membranes were fabricated by incorporating different contents of P-MOFs into Am-SPAEKS polymer matrix using non-solvent-induced phase separation. The morphology, chemical structure and properties of the polymers, fillers and composite membranes were proved by FT-IR, 1H NMR, FE-SEM, XPS and etc. The final experimental results showed that the introduction of hydrophilic fillers, P-MOFs, substantially improved the hydrophilicity, water flux and antifouling capabilities of the membranes. The water contact angle decreased from 78.5° to 56.4°. The flux of water from a pure membrane was 333.68 L/m2 h. When the content of P-MOFs was 0.1 %, the water flux could attain to 830.23 L/m2 h, the retention rate of bovine serum albumin (BSA) solution could attain to 98.6 % and the flux recovery rate (FRR) values of the composite membrane remained high (86.1 %) for BSA solution. In addition, after three cycles, the pure water flux of the composite membrane could still attain 595.49 L/m2 h. The results demonstrated that P-MOFs have significant potential for utilization in the preparation of composite ultrafiltration membranes and provided an effective idea for the modification and design of other hydrophilic MOFs applied in the study area of ultrafiltration membranes.

Generalised Neuronal Calcium Dynamics of Membrane and ER in the Polar Dimension.

Calcium ions are the second messenger playing as regulators for various cellular activities. Its spatiotemporal control is critical for various brain functions, including neuroplasticity, apoptosis, and cell death. The Endoplasmic Reticulum (ER) plays an important role in determining these spatiotemporal calcium dynamics. Stromal interaction molecule (STIM) - Orai channel on the membrane generates additional calcium flow, whereas other membrane fluxes contribute to cytosolic flux. Due to their anomalous character, we used the Caputo fractional differential operator to mimic these interactions in polar coordinates. Solutions were generated using hybrid integral transform methods to control the analytical approach. Using Green's function yielded a closed-form solution for Mittag-Leffler-type functions. This work emphasizes the significant relationship between calcium and various buffer levels in neurons. The differential transition simulation of a time derivative with space across different parameters indicated a decrease in calcium concentration. Anomalously low buffer levels exhibited the impact of Alzheimer's disease on calcium higher concentration, leading to the death of neurons. Additionally, the research introduces a method involving S100B, BAPTA, and calmodulin buffers to uphold optimal calcium levels within the neuronal cytosol. The applicability of this model with different buffer properties and parameters and memory impacts the calcium concentration with the neurological disorder.

Polyamidoamine dendrimer-modified polyvinylidene fluoride microporous membranes for protein separation

The separation efficiency of pressure-driven filtration membranes is primarily dictated by the membrane pore size. Membranes with larger pores typically demonstrate high flux but low or zero rejection when it comes to separating small molecules. In protein separation, ultrafiltration (UF) membranes with pore sizes smaller than the molecular dimensions of target proteins are commonly used for size rejection. Taking inspiration from the separation mechanism of nanofiltration (NF) membranes, we hypothesize that introducing charged groups into membranes of appropriate pore sizes could significantly enhance the electrical interaction between membrane charges and protein charges. This enhancement, occurring at the nanoscale distance when protein molecules approach or pass through charged nanoscale membrane channels, may enable the rejection of proteins substantially smaller than the pore size. Using membranes with relatively large pore sizes could lead to an increase in flux. To test this hypothesis, we conducted experiments involving the modification of polyvinylidene fluoride (PVDF) membranes with suitable pore sizes, using polyamidoamine (PAMAM) dendrimers to introduce negative charges to the membranes. The performance of the PVDF membranes and the modified membranes were investigated in the separation of whey proteins. To evaluate the contribution of steric and electrical hindrance to the solute separation, filtration experiments were performed using polyethylene oxide (PEO) and polyacrylic acid (PAA). The membranes were characterized using techniques such as attenuated total reflectance-Fourier transform infrared (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The results indicate that the modification enhances the rejection efficiency of whey proteins. The whey protein rejection and permeate flux for PVDF membranes were 58.9% and 15.3 LMH, respectively. Following alkaline treatment or PAMAM-G3.5 dendrimer modification, the whey protein rejection increased to 97.3% and 98.8%, respectively. However, alkaline treatment and PAMAM-G3.5 dendrimer modification resulted in a reduction of permeate flux to 5.6 LMH and 2.3 LMH, respectively. This suggests that increasing membrane charge effectively enhances the separation ability of filtration membranes in charged macromolecule separation.

A High-Quality Mixed Matrix Membrane with Nanosheets Assembled and Uniformly Dispersed Fillers for Ethanol Recovery.

A high-quality filler within mixed matrix membranes, coupled with uniform dispersity, endows a high-efficiency transfer pathway for the significant improvement on separation performance. In this work, a zeolite-typed MCM-22 filler is reported that is doped into polydimethylsiloxane (PDMS) matrix by ultrafast photo-curing technique. The unique structure of nanosheets assembly layer by layer endows the continuous transfer channels towards penetrate molecules because of the inter-connective nanosheets within PDMS matrix. Furthermore, an ultrafast freezing effect produced by fast photo-curing is used to overcome the key issue, namely filler aggregation, and further eliminates defects. When pervaporative separating a 5 wt% ethanol aqueous solution, the resulting MCM-22/PDMS membrane exhibits an excellent membrane flux of 1486g m-2 h-1 with an ethanol separation factor of 10.2. Considering a biobased route for ethanol production, the gas stripping and vapor permeation through this membrane also shows a great enrichment performance, and the concentrated ethanol is up to 65.6 wt%. Overall, this MCM-22/PDMS membrane shows a high separation ability for ethanol benefited from a unique structure deign of fillers and ultrafast curing speed of PDMS, and has a great potential for bioethanol separation from cellulosic ethanol fermentation.

Effect of sintering temperature on ceramic membrane fabricated using coal flyash and natural clay for lignin recovery

This study explores the utilization of coal fly ash combined with natural clay as a precursor for creating ceramic membranes through the uniaxial compaction method, aiming at lignin separation. These membranes were sintered at varying temperatures from 600 to 1000 °C. Thermal Gravimetric Analysis (TGA) revealed the robust thermal stability of the membranes. Fourier Transform Infrared (FTIR) analysis affirmed the presence of silica and alumina within the membranes. X-ray Diffraction (XRD) peaks indicated the crystalline structure and the presence of metal oxides originating from the fly ash and clay components. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) images illustrated the porous nature and rough surface of the ceramic membranes. The average pore radius of the fabricated membrane expanded from 43.12 to 7.91 nm with increasing temperature. Concurrently, membrane flux decreased from 4.13 to 0.96 ×10−6 m3/m2 s with higher temperatures. Lower contact angles indicated the hydrophilic properties of membranes. All membranes exhibited superior corrosion resistance and negative zeta potential, owing to the significant silica content in the fly ash. Lignin separation efficiency increased from 65 % to 81 % with increasing temperatures. The optimal sintering temperature was determined to be 800 °C, achieving a lignin recovery greater than 76 % and a membrane permeability of about 7×10−9 m3/m2 s kPa. Thus, the fly ash-clay-based ultrafiltration membranes synthesized in this study offer the potential for lignin biomass recovery from biorefinery effluent.

One-step exfoliation and etching of layered double hydroxide nanosheets to construct nanofiltration membranes with high water permeance

Two-dimensional nanosheets are considered promising materials for membranes. However, the excessively long interlayer channels parallel to the membrane surface are not conducive to molecular transport. Creating defects on the nanosheets is an effective method to shorten the transport distance in the membrane. This study involved exfoliating and etching several commonly used layered double hydroxide (LDH) nanosheets using an alkali solution in a single step. This process resulted in porous oligolayered nanosheets modified layered double hydroxide (MgAl-MLDH) with an average pore size of approximately 18 ± 2 nm and a thickness of around 8 nm. These ultrathin porous MgAl-MLDH nanosheets were used to create a composite membrane using a vacuum-assisted filtration method. The structure of the MgAl-MLDH membrane was optimized by adjusting the etching conditions. The water flux of MgAl-MLDH membrane in Eriochrome black T aqueous solution was 530 L/m2 h MPa. Compared with the non-etched LDH membrane (179 L/m2 h MPa), the permeance of MLDH membrane was increased by 2 to 3 times, while the rejection rate remained at approximately 99 %. Furthermore, due to the excellent strength of LDH, the membrane exhibited good stability in both structure and separation performance.

In situ polymerization of a poly(3,4-ethylenedioxythiophene):poly(sodium–styrennesulfonate) conductive layer for electro-assisted ultrafiltration and fouling mitigation

Electrification can enhance the antifouling performance of ultrafiltration membranes and improve the sustainability of membrane technologies. The design of high-performance conductive membrane materials remains one of the core technologies in electro-assisted ultrafiltration. Here, conductive PVDF/PEDOT:PSS composite membranes were prepared via in situ chemical oxidation polymerization on a PVDF surface. The PVDF/PEDOT:PSS membranes were subsequently used for electro-filtration to study the effect of the applied potential on humic acid fouling. When a voltage of 3 V was applied, the PVDF/PEDOT:PSS20 membrane was continuously polluted for 5 cycles. The results showed that after simple hydraulic cleaning, the membrane flux recovery rate reached 91 %. Compared with that of the PVDF membrane, the irreversible fouling of the PVDF/PEDOT:PSS20 membrane decreased by 65 %. The modified Poisson Boltzmann equation indicates that applying cathodic potential on the surface of PEDOT:PSS conductive layer increases the cumulative concentration of counter ions on the membrane surface and the thickness of the charged layer, thereby promoting the migration of peak forces on the membrane surface to the bulk solution, changing the fouling behaviour of HA from cake filtration to standard blocking.

A novel nanofiltration membrane with a dual-charged layer to simultaneously remove anions and cations from acid mine drainage

A novel nanofiltration (NF) membrane with a positively and negatively dual-charged layer was finely designed in this study. The membrane was prepared by co-deposition of 4-tert-butylpyrocatechol (TBC) and polyethyleneimine (PEI) and electrostatic interaction to assemble positively and negatively charged functional layers on a substrate which is polyamide (PA)-based NF membrane. The NF membrane achieved excellent retention capacity through the combined effects of Donnan repulsion and electrostatic field trapping. The prepared membrane had a dense but thin surface layer with an average pore size of 0.84 nm, enabling an improved membrane flux of 8.66 L/(m2·h·bar) and high rejection to divalent inorganic salt ions (93.56 % Mg2+, 99.56 % SO42-). The membrane was used to treat acid mine drainage (AMD) and achieved an excellent retention capacity for ions in AMD (93.25 % Mg2+, 91.58 % Ca2+, 94.22 % Mn2+, 95.96 % SO42-), meeting industrial wastewater discharge standards. In addition, the NF membrane demonstrated good anti-fouling performance during the AMD treatment and significant potential for environmental remediation applications.

Alkaline stability of polyester nanofiltration membranes prepared by interfacial polymerization

Polyester nanofiltration membranes typically outperform traditional polyamide alternatives in fouling resistance, water flux, and chlorine tolerance. However, their alkali resistance remains poorly understood. This study investigates the stability of polyester membranes, prepared via interfacial polymerization of eight hydroxyl monomers with TMC, in alkaline conditions (pH 12.4). We systematically recorded changes in water flux and solute rejection and employed SEM, AFM, zeta-potential, contact angle analysis, and XPS to examine physicochemical structural changes during hydrolysis. The findings reveal that most membranes are susceptible to alkaline hydrolysis, evidenced by increased water flux and decreased rejection rates. Specifically, membranes derived from pyrogallol-based hydroxyl monomers exhibited the greatest instability, whereas those incorporating sodium alginate demonstrated remarkable stability. After immersion in water, the water flux of the TA membrane increased from 8.4 to 21.2 Lm−2h−1bar−1 and the rejection rate decreased from 36.6 % to 12.1 %. the water flux of PG membrane was from 22.0 to 54.2 Lm−2h−1bar−1, while the rejection rate decreased from 60.2 % to 22.7 %. DFT calculations corroborate these observations, linking ester bond energies with membrane stability. This study not only advances our understanding of polyester nanofiltration membrane properties but also highlights critical vulnerabilities in alkali environments, guiding future improvements.

Expanded polystyrene (EPS) waste upcycling and efficient oil/water emulsion separation with advanced EPS-cotton membranes

The current work describe the fabrication of an oleophilic and hydrophobic EPS-cotton membrane through a facile one-step process, involving the immersion of pristine cotton fabric in a freshly prepared solution of EPS in tetrahydrofuran (THF). The characterization of EPS-cotton membrane is carried out using FTIR spectroscopy, scanning electron microscopy (SEM), and contact angle measurements. The EPS-cotton membrane exhibits remarkable absorption capacity for diesel, gasoline, olive oil, and canola oil, i.e., 0.21 gg−1, 0.13 gg−1, 3.7 gg−1 and 0.40 gg−1, respectively. Using vacuum filtration, the membrane effectively segregates diesel oil, gasoline, olive oil, and canola oil emulsions from water. The flux of membrane for diesel oil, gasoline, olive oil, and canola oil emulsions with water is found to be 133 LMH, 207 LMH, 59 LMH and 89 LMH, respectively. Moreover, the water rejection (%) remains above 95 % in all cases. The separated samples are monitored through FTIR and UV/Vis, which suggests high separation efficiency of EPS-cotton membrane. Furthermore, FTIR and SEM analyses of EPS-cotton membrane before and after separations demonstrate suitable membrane stability, allowing for at least six cycles of effective use. EPS-cotton membrane fabrication not only facilitates the eco-friendly recycling of waste plastics but also promises versatile applications in environmental remediation.

Study on membrane fouling mechanisms and mitigation strategies in a pilot-scale anaerobic membrane bioreactor (P-AnMBR) treating digestate

Anaerobic Membrane Bioreactor (AnMBR) are employed for solid-liquid separation in wastewater treatment, enhancing process efficiency of digestion systems treating digestate. However, membrane fouling remains a primary challenge. This study operated a pilot-scale AnMBR (P-AnMBR) to treat high-concentration organic digestate, investigating system performance and fouling mechanisms. P-AnMBR operation reduced acid-producing bacteria and increased methane-producing bacteria on the membrane, preventing acid accumulation and ensuring stable operation. The P-AnMBR effectively removed COD and VFA, achieving removal rates of 82.3 % and 92.0 %, respectively. Higher retention of organic nitrogen and lower retention of ammonia nitrogen were observed. The membrane fouling consisted of organic substances (20.3 %), predominantly polysaccharides, and inorganic substances (79.7 %), primarily Mg ions (10.1 %) and Ca ions (4.5 %). To reduce the increased transmembrane pressure (TMP) caused by fouling (a 10.6-fold increase in filtration resistance), backwash frequency experiment was conducted. It revealed a 30-min backwash frequency minimized membrane flux decline, facilitating recovery to higher flux levels. The water produced amounted to 70.3 m³ over 52 days. The research provided theoretical guidance and practical support for engineering applications, offering practical insights for scaling up P-AnMBR.

ABPBI-based hollow fiber membranes for forward osmosis (FO) possessing low reverse salt flux

The poly(2,5-Benzimidazole), known for its excellent thermochemical stability, was evaluated as a membrane material for forward osmosis. The dope in methane sulfonic acid was used to make hollow fiber membranes. The availability of bound MSA in HFMs was compared with its neutral form. Aqueous solutions of two common salts reported for FO (NaCl and MgCl2) were used as a draw solution at varying concentrations. The performance was determined in terms of water flux and reverse salt flux. The long-term performance of the membrane was assessed. The heat pretreatment of membranes was beneficial in offering low reverse salt flux, a crucial parameter in FO. The heat treatment at 350 °C exhibited excellent performance of low-RSF, irrespective of the draw solute used. The presence of MSA in the membrane matrix was found to be beneficial. Present HFMs exhibited reverse salt flux as low as 0.003 mol m−2 h−1 using 2 mol L−1 MgCl2 as a draw solution. The water flux of present membranes was lower than that of reported FO-membranes, which is attributable to the larger thickness of the present membranes. The findings will be used to make ABPBI-based membranes in thin form to elevate the fluxes and their practical applicability.

Dehydration of bioethanol using novel polysulfone (PSF)/nonionic surfactants hybrid membranes

This study focuses on developing a novel polysulfone (PSF) dense hybrid membrane modified with nonionic surfactants, Tween 20 (T20) and Triton X-100 (X100), for improved pervaporation (PV) dehydration of bioethanol. The modified membranes were then examined for their ethanol dehydration performance, microscopy and spectroscopy characteristics, surface charge, mechanical and roughness properties, crystallinity structure, differential scanning calorimetry (DSC), swelling, and contact angle (CA) analysis. The free volume structure of the membranes was assessed using positron annihilation lifetime spectroscopy (PALS) and Doppler broadening spectroscopy (DBS). A significant discovery from this analysis was the semi antiplasticizing effect observed when surfactants were added to the PV membranes. The PV results revealed that incorporating 0.5 wt% T20 into PSF significantly improved the total flux and PSI of PSF/T20 to 226.35 g/m2 h and 46578 g/m2 h, respectively. Similarly, the total flux and PSI of hybrid membranes containing X100 increased to 110.19 g/m2 h and 43680 g/m2 h. Consequently, the developed PSF/T20 membranes demonstrated more significant potential for bioethanol dehydration compared to PSF/X100 membranes.

Stratified structure of membrane clogs observed in full scale cross-flow tubular ultrafiltration (UF) system: Fouling characterization and a proposed two-stage formation mechanism

Membrane fouling remains a significant challenge in wastewater treatment, hindering both efficiency and lifespan. This study reports a distinct phenomenon of stratified membrane clogging observed in a full-scale cross-flow tubular ultrafiltration (UF) system treating sludge anaerobic digestion (AD) reject water. The distinct stratified structure, comprising inner and outer layers within the cake layer, has not been previously described. This research involved characterizing the filtration performance, analyzing membrane clog composition, and proposing a two-stage formation mechanism for the stratified clogs. It was revealed that higher inorganic and lower organic content in the outer layer compared to the inner layer. Acid and alkali treatments demonstrated the effectiveness of combined cleaning strategies. A mathematical model was developed to determine the critical conditions for stratified clog formation, influenced by membrane flux and cross-flow velocity (CFV). It is proposed that outer layer forms through long-term selective deposition, while the inner layer results from short-term dewatering within limited tubular space. High CFV (>2.5 m/s) prevents inner layer formation. Critical conditions for stratification occur at a flux of 18 L/m2/h with a CFV of 0.1 m/s or 65 L/m2/h with a CFV of 0.35 m/s. This study contributes a novel understanding of stratified membrane clogging, proposing a two-stage formation mechanism and identifying critical conditions, which provides insights for effective fouling control strategies and maintenance of operational efficiency for membrane systems.

Preparation of Graphene Oxide (GO) incorporated-Polyvinylidene Fluoride (PVDF) Nanofiltration Membrane with Alkaline Post-Treatment for Textile Wastewater Treatment

The purpose of this research is to study the potential of polyvinylidene fluoride (PVDF) polymer incorporated with graphene oxide (GO), following with the alkaline etching post-treatment process for dye waste water treatment. Its anti-oxidation properties of PVDF, have led to its choice as a host polymer due to its high thermal stability, great organic selectivity, and excellent chemical and mechanical resistance. In addition, the post-treatment with a NaOH solutions of varied concentration ranging from 0 M to 0.2 M for 30 minutes was conducted in alter the morphology of the fabricated membrane with the aim to increase the perm-selectivity of the membranes. Besides, the fabricated membranes were further characterized in terms of the chemical and physical properties using Fourier-Transform Infrared Spectroscopy (FTIR), Contact Angle (CA), Ultraviolet Visible spectroscopy (UV-Vis), Atomic Microscopy (AFM) and Scanning Electron Microscopy (SEM). The experimental results showed that the post-treatment has decreased the membrane flux of dye wastewater. Based on the obtained result, as the concentration of NaOH solution increased, the permeability increased. While the overall dye rejection of the membrane remained of above 90 %.

Asymmetric PDMS/PVDF Pervaporation Membrane for Separation of Ethanol/Water System

AbstractPreparing asymmetric pervaporation membranes is a kind of promising method to enhance pervaporation membrane flux. Hydrophobic PVDF polymer can be used to prepare asymmetric pervaporation membranes, but its separation factor is relatively low. In this work, to improve the performance of PVDF membrane pervaporation, PDMS polymer was added to the PVDF membrane, and asymmetric PDMS/PVDF permeable membranes were prepared by the non‐solvent induced phase separation (NIPS) method. The effects of mass ratios of PDMS to PVDF on the membrane structures and the membrane properties were characterized by SEM, XRD, FTIR, TGA, water contact angle and mechanical strength. The results showed that the ratios of the PDMS: PVDF affect its phase‐separation behavior. As the addition of PDMS increased, the finger‐like pores on the membrane section gradually became longer, the upper surface changed from less porous to porous structure, and the lower surface structure changed from interconnected flocculent structure to porous, and the best structure of the blend membrane was achieved when the PDMS: PVDF mass ratio was 1 : 5. Therefore, the membrane had the best separation performance in separating 15 wt. % ethanol aqueous solution with a permeate total flux of 273.65 g/(m2 h) and a separation factor of 9.09 when the mass ratio of PDMS: PVDF was 1 : 5.

Engineering polyvinylidene fluoride membranes using charge tunable dendrimer polyamidoamine to enable microporous membranes for protein separation

Dendrimers are structurally precise molecules, whose peripheral layer provides ample sites for anchoring functional groups of different charges and charge densities. This characteristic renders them capability of providing numerous target functional groups on the surface of filtration membranes when modified by dendrimers. Consequently, there has been a growing interest in dendrimer-modified membranes. In this study, we investigated the engineering of polyvinylidene fluoride (PVDF) membranes using polyamidoamine (PAMAM) dendrimers anchoring different functional groups to tune the charges and charge density of membranes to enable microporous membranes for separation of charged macromolecules. PVDF membranes were functionalized by grafting PAMAM-G3.0 (generation 3) dendrimers with amine groups onto their surfaces and internal surfaces of membrane pores. Subsequently, the peripheral functional groups of dendrimers on the membranes were replaced by carboxyl groups, quaternary ammonium groups, or sulfonic acid groups for charges of different nature and densities. Surface chemical properties, electrical properties, and morphology were characterized using various techniques, including attenuated total reflectance Fourier-transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and surface zeta potential measurement. The filtration performance of both PVDF and modified membranes was evaluated using polyethylene oxide (PEO), polyacrylic acid (PAA), and whey protein filtration. Among the modified membranes, the G3PA membranes, with carboxyl functional groups, exhibited the most effective whey protein separation performance. The whey protein rejection and permeate flux of the G3PA membranes were 79 % and 30.3 LMH, respectively. As a comparison, the whey protein rejection and permeate flux of the pristine PVDF membranes were 58.9 % and 15.3 LMH, respectively.

Mechanical Enhancement and Water Treatment Efficiency of Nanocomposite PES Membranes: A Study on Akçay Dam Water Filtration Application.

Polymeric membranes are widely used in water treatment because of their ease of fabrication and low cost. The flux and purification performance of membranes can be significantly improved by incorporating appropriate amounts of nanomaterials into the polymeric membrane matrices. In this study, neat poly(ether sulfone) (PES), PES/nano copper oxide (CuO), and PES/nano zinc oxide (ZnO) membranes are fabricated via phase inversion. The pure water flux of the neat PES membrane, which is 355.14 L/m2·h, is increased significantly with the addition of nano-CuO and nano-ZnO, and the pure water fluxes of the nanocomposite membranes vary in the range of 392.65-429.74 L/m2·h. Moreover, nano CuO and nano ZnO-doped PES nanocomposite membranes exhibit higher conductivity, color, total organic carbon, boron, iron, selenium, barium, and total chromium removal efficiencies than neat PES membranes. The membrane surfaces examined by Scanning Electron Microscopy (SEM) after water filtration revealed that those containing 0.5% wt. nano CuO and nano ZnO are more resistant to fouling than the membrane surfaces containing 1% wt. nano CuO and nano ZnO. Based on the results of this study, 0.5% wt. nano ZnO-doped PES membrane is found to be the most suitable membrane for use in water treatment due to its high pure water flux (427.14 L/m2·h), high pollutant removal efficiency, and high fouling resistance. When the mechanical properties of the membranes are examined, the addition of CuO and ZnO nanoparticles increases the membrane stiffness and modulus of elasticity. The addition of 0.5% and 1% for CuO leads to an increase in the modulus of elasticity by 57.95% and 324.43%, respectively, while the addition of 0.5% and 1% for ZnO leads to an increase in the modulus of elasticity by 480.68% and 1802.43%, respectively. At the same time, the tensile strength of the membranes also increases with the addition of nanomaterials.