Membrane Surface Research Articles

Targeting Caveolin-1 in Multiple Myeloma Cells Enhances Chemotherapy and Natural Killer Cell-Mediated Immunotherapy.

The cell membrane transport capacity and surface targets of multiple myeloma (MM) cells heavily influence chemotherapy and immunotherapy. Here, it is found that caveolin-1 (CAV1), a primary component of membrane lipid rafts and caveolae, is highly expressed in MM cells and is associated with MM progression and drug resistance. CAV1 knockdown decreases MM cell adhesion to stromal cells and attenuates cell adhesion-mediated drug resistance to bortezomib. CAV1 inhibition in MM cells enhances natural killer cell-mediated cytotoxicity through increasing CXCL10, SLAMF7, and CD112. CAV1 suppression reduces mitochondrial membrane potential, increases reactive oxygen species, and inhibits autophagosome-lysosome fusion, resulting in the disruption of redox homeostasis. Additionally, CAV1 knockdown enhances glutamine addiction by increasing ASCT2 and LAT1 and dysregulates glutathione metabolism. As a result of CAV1 inhibition, MM cells are more sensitive to starvation, glutamine depletion, and glutamine transporter inhibition, and grow more slowly in vivo in a mouse model treated with bortezomib. The observation that CAV1 inhibition modulated by 6-mercaptopurine, daidzin, and statins enhances the efficacy of bortezomib in vitro and in vivo highlights the translational significance of these FDA-approved drugs in improving MM outcomes. These data demonstrate that CAV1 serves as a potent therapeutic target for enhancing chemotherapy and immunotherapy for MM.

Kv4 channels improve the temporal processing of auditory neurons in the cochlear nucleus.

Kv4 channels generate A-type current known to regulate neuronal excitability. Its role in processing timing information is understudied, especially in the auditory system where temporal information is crucial for hearing. In the cochlear nucleus, principal bushy neurons are specialized for temporal processing with distinct biophysical properties owing to their expression of various voltage-gated ion channels. Previous studies reported conflicting information regarding the expression and potential role of Kv4 channels in these neurons. We explored these questions using electrophysiology in CBA/CaJ mice of either sex. A-type current was isolated from 88% of bushy neurons using Kv4 channel-selective blocker Jingzhaotoxin-X (JZ-X), which increased the intrinsic excitability of bushy neurons without altering their synaptic input. During high-rate activity, JZ-X treatment significantly increased the spike jitter and reduced the firing threshold of bushy neurons. In old mice, A-type current in bushy neurons reduced in magnitude but maintained current density, accompanied by decreased membrane surface area. In contrast, TEA-sensitive Kv3 current reduced in both magnitude and current density, indicative of a greater contribution to the altered biophysical properties of bushy neurons during ageing. Our findings suggest that Kv4 channels play significant roles in regulating neuronal excitability and improving the temporal processing of bushy neurons. Such function is likely retained with age and is not the primary mechanism driving compromised temporal processing under age-related hearing loss. KEY POINTS: Most bushy neurons of the cochlear nucleus exhibit Kv4-mediated A-type current. A-type current regulates neuronal excitability of bushy neurons without contributing to the synaptic transmission at the endbulb of Held. A-type current increases the firing threshold and improves the temporal precision of spikes in bushy neurons during high-rate activity. A-type current reduces peak amplitude in bushy neurons during ageing but maintains current density. Decreased Kv3 current, rather than Kv4 current, likely play more significant roles in altering the biophysical properties of bushy neurons during ageing, contributing to compromised temporal processing during age-related hearing loss.

Sustainable synthesis and environmental application of chitosan-Ocimum basilicum leaves-ZnO composite membrane for permanganate ion removal in wastewater treatment.

This study introduces a novel and environmentally friendly method for developing a cross-linked chitosan-Ocimum basilicum leaves-ZnO (ChOBLZnO) composite membrane, specifically designed for the adsorption of permanganate ions (MnO4-) from wastewater. Various characterization techniques, including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) surface area analysis, were employed to confirm the membrane's synthesis quality, structural integrity, and surface properties crucial for adsorption. The BET analysis revealed a surface area of 228.64 m2/g, indicating a highly porous structure. The membrane exhibited a high adsorption capacity of 142.8mg/g and an outstanding removal efficiency of 98.5%. The adsorption kinetics were best described by the pseudo-second-order model, with a correlation coefficient (R2) of 0.998, while the Freundlich isotherm model provided the most accurate fit for the adsorption behavior, with an R2 of 0.995. Thermodynamic studies indicated that the adsorption process is spontaneous and endothermic, with negative Gibbs free energy and positive enthalpy and entropy values. Reusability tests showed that the ChOBLZnO composite membrane maintained a high removal efficiency across five cycles, with minimal performance loss. These results demonstrate the ChOBLZnO composite membrane's potential as an efficient and sustainable solution for wastewater treatment, offering both high efficiency and durability.

Biofouling evolution driven by autoinducer-2 quorum sensing in reverse osmosis (RO) for water reclamation

Membrane biofouling remains a key challenge for reverse osmosis (RO) technology in water reclamation. This study investigated the biofouling development with time on RO membrane surface. During the biofouling evolution, the biofilm was examined through confocal laser scanning microscopy (CLSM) observation and foulant composition analysis. Results showed that organic/biofouling was the key contributor, and autoinducer-2 (AI-2), quorum sensing (QS) signaling molecules, were found to play an important role in coordinating community-level behaviors associated with RO membrane fouling. In the initial stage of fouling layer development, the attached cell and biopolymer contents increased with rising AI-2 activity. As development continued, the microbial community changed remarkably, exhibiting peak AI-2 activity as the membrane surface became fully covered with cells and the EPS matrix. However, in later stages, despite a decrease in AI-2 content and biological activity, the rate of increase in fouling resistance accelerated significantly due to continually accumulating foulants. As a result, the AI-2 QS was crucial during early phases of biofilm development in RO systems. This study helps to look deeply into the biological fundamentals of AI-2 mediated QS in RO fouling, enhancing the understanding of the mechanisms behind RO membrane fouling in water reclamation, and may facilitate the development of anti-fouling strategies.

Development of a Negatively Charged Polyether Sulfone Membrane Enriched with MIL-101(Cr)-Modified Magnetic Activated Pyrolytic Coke for Enhanced Dye Removal, Permeability, and Antifouling Properties

Developing high-performance nanofiltration membranes for effectively treating wastewater contaminated with organic pollutants has become increasingly important. Given the hazardous nature of these contaminants, proper treatment of wastewater is crucial before it is released into natural water bodies. This study synthesized a novel composite membrane by incorporating Fe3O4@APC@MIL-101(Cr) nanocomposites into a polyether sulfone (PES) matrix using a phase inversion technique. The inclusion of 0.5wt.% Fe3O4@APC@MIL-101(Cr) significantly enhanced the membrane's hydrophilicity, porosity, and surface characteristics. The optimized membrane achieved an impressive pure water flux (PWF) of 90.24L/m²h, reflecting a 400% improvement over pristine PES membranes. Moreover, it exhibited excellent rejection rates of 97.21% for crystal violet (CV) and 99.43% for methylene blue (MB), alongside a rejection efficiency of 57.73% for the anionic dye methyl orange (MO). The antifouling performance was notably improved, as evidenced by an increase in the flux recovery ratio (FRR) from 46% for bare PES membranes to 81.11% for hybrid membranes. Additionally, the effects of various salt types on the membrane's separation performance were investigated. The Fe3O4@APC@MIL-101(Cr) modified PES membranes demonstrate significant potential as effective candidates for treating wastewater contaminated with dye pollutants.

Advanced PPS/MOFs composite nanofiltration membranes derived from contra-diffusion synthesis for precise molecular separation

To meet the separation requirements of polyphenylene sulfide (PPS) membranes in extremely harsh environments and to enhance the separation performance of PPS membrane material, this study utilizes Zeolitic imidazolate framework (ZIF) material with a porous structure to modify the structure of the PPS membranes. Using the Contra-diffusion synthesis method, we successfully created PPS composite membranes that were modified by ZIF-8. At the end of the three-hour reaction time, a continuous and dense layer of ZIF-8 crystals with uniform crystal size and regular crystal shape was produced on the matrix membrane's surface. The permeance to rhodamine B aqueous solution is 42.54 L m−2 h−1 bar−1, and the retention rate is 99.5 %, which has high permeability and retention performance. In the anti-pollution performance test, the composite membrane's flux recovery rate is 72.9 %, which has good anti-pollution performance. After immersion in strong acids, strong alkalis, and a variety of organic solvents, the appearance shows no evident flaws, and the separation performance in strong alkalis and five different types of organic solvents stays steady, demonstrating excellent alkali and solvent resistance. This proves that composite membranes have great potential for application in dye wastewater treatment.

Surface- and substrate-coated catalytic membrane for mitigating interference of water matrix species in intensified micropollutant confinement oxidation

The integration of advanced oxidation processes (AOPs) with membrane technology offers benefits for catalyst recovery and reducing membrane fouling. However, the application of the hybrid process could be hampered by the background species in water matrix. This study addresses this challenge by developing catalytic ceramic membranes (CCMs) with dual mechanisms to intensify acetaminophen (ACT) removal in water. The CCMs effectively activated peroxymonosulfate (PMS), achieving ACT degradation of 85% and 93% in real water matrices (reverse osmosis retentate and settled water, respectively) and 99% in MQ water. The CCMs demonstrated consistent performance across multiple operational cycles, even in the presence of humic acid (HA) (96% ACT reduction). The CCM design features Co3O4 catalytic layer on CCM surface, facilitating surface oxidation, reducing fouling, and TiO2 intermediate rejection layers serving as barrier for bulk organic pollutants, achieving 50% HA removal through rejection and 70% with 1.5mM PMS. This design facilitates catalytic degradation at the membrane surface, allowing retention and degradation of bulk organic pollutants and intermediates, while ACT permeates into CCM substrate. The surface oxidation and rejection enhanced confinement oxidation within the Co3O4-coated macropores, minimizing interference from background species. LC-QTOF analysis identified multiple degradation pathways, including hydroxylation, acetyl-amino group cleavage, side chain oxidation and benzene ring cleavage, with intermediates showing reduced toxicity. Reactive oxygen species involved in the system were identified and PMS activation mechanism was proposed. This research highlights the potential of the hybrid process, enhancing micropollutant removal by mitigating interference from background species, providing practical implications in water treatment applications.

Fabrication of an antibacterial polybenzimidazole/Ag@UiO-66-NH2 mixed matrix membrane for dye-salt separation: Solvent evaporation effects

In textile water treatment, nanofiltration membranes are susceptible to biofilm layer formation on their surface due to microbial colonization, which can significantly reduce the separation efficiency of the membrane. Therefore, maintaining long-term antimicrobial efficacy of the membrane is of paramount importance. In this study, UiO-66-NH2 nanoparticles were fabricated via the solvothermal method, then Ag-loaded UiO-66-NH2 (Ag@UiO-66-NH2) nanoparticles were produced by stirring and reduction with silver nitrate solution, and the nanoparticles were integrated into the polybenzimidazole (PBI) matrix through a blending process to fabricate mixed matrix membranes (MMMs) with antimicrobial properties. During the preparation of mixed matrix membranes, the phenomenon of nanoparticle agglomeration on the membrane surface is frequently encountered. In order to solve this problem, we used solvent evaporation and cross-linking post-treatment methods to further improve the compatibility between the membrane and the particles, the membranes showed a good water flux (53.7 L·m−2·h−1), excellent separation capabilities for dyes and salts, NaCl rejection (9.50 %), Na2SO4 rejection (12.70 %), MgCl2 rejection (7.44 %), MgSO4 rejection (9.34 %), Crystal violet, Acid fuchsin, Congo red, Coomassie brilliant blue and Acid red 94 dyes rejection (all over 99 %). And the antibacterial rate is 98.7 % against E. coli and 99.1 % against S. aureus and it has the function of long-term stable Ag+ release.

Three birds with one stone: Preparation of multifunctional Fe-MOF/PAN nanofiber membranes for wastewater treatment

In this research, a new NH2-MIL-88B(Fe)/polyacrylonitrile nanofiber membrane (NPNFM) was synthesized utilizing a straightforward electrospinning technique. The morphological characteristics and performance of nanofiber membranes were finely tuned via adjusting the dosage of NH2-MIL-88B(Fe) (NM88B, the “stone”). The prepared NPNFM exhibits superhydrophilicity/underwater superoleophobicity, coupled with outstanding photo-Fenton self-cleaning ability (the first two “birds”). This membrane efficiently and swiftly facilitated the separation of various surfactant-stabilized emulsions under gravitational force, achieving a separation efficiency and flux of up to 99.5 % and 350.3 L m-2h−1, respectively. The fouling on the membrane surface can be rapidly decomposed, attributing to the superior photo-Fenton activity of NM88B. Furthermore, the organic dye methylene blue (MB) was degraded by 97.4 % within 40 min under the catalytic influence of the membrane. The nanofiber membrane has good mechanical properties and its tensile strength is about 2.3 times that of the original membrane attributing to the good compatibility between NM88B and the membrane matrix (the third “bird”). This study proposed new Fe-MOF-based photo-Fenton multifunctional membranes with the characteristics of environmental stability and high efficiency in wastewater treatment fields.

Nucleic acid-binding KH domain proteins influence a spectrum of biological pathways including as part of membrane-localized complexes

K-Homology domain (KH domain) proteins bind single-stranded nucleic acids, influence protein–protein interactions of proteins that harbor them, and are found in all kingdoms of life. In concert with other functional protein domains KH-domains contribute to a variety of critical biological activities, often within higher order machineries including membrane-localized protein complexes. Eukaryotic KH domain proteins are linked to developmental processes, morphogenesis, and regulation, and their aberrant expression is often associated with cancer. Prokaryotic KH domain proteins are involved in integral cellular activities including cell division and protein translocation. Eukaryotic and prokaryotic KH domains share structural features, but are differentiated based on their structural organizations. In this review, we explore the structure/function relationships of known examples of KH domain proteins, and highlight cases in which they function within or at membrane surfaces. We also summarize examples of KH domain proteins that influence bacterial virulence and pathogenesis. We conclude the article by discussing prospective research avenues that could be pursued to better investigate this largely understudied protein category.

MiRNA packaging into small extracellular vesicles and implications in pain.

Extracellular vesicles (EVs) are a heterogenous group of lipid bilayer bound particles naturally released by cells. These vesicles are classified based on their biogenesis pathway and diameter. The overlap in size of exosomes generated from the exosomal pathway and macrovesicles that are pinched off from the surface of the plasma membrane makes it challenging to isolate pure populations. Hence, isolated vesicles that are less than 200 nm are called small extracellular vesicles (sEVs). Extracellular vesicles transport a variety of cargo molecules, and multiple mechanisms govern the packaging of cargo into sEVs. Here, we discuss the current understanding of how miRNAs are targeted into sEVs, including the role of RNA binding proteins and EXOmotif sequences present in miRNAs in sEV loading. Several studies in human pain disorders and rodent models of pain have reported alterations in sEV cargo, including miRNAs. The sorting mechanisms and target regulation of miR-939, a miRNA altered in individuals with complex regional pain syndrome, is discussed in the context of inflammation. We also provide a broad overview of the therapeutic strategies being pursued to utilize sEVs in the clinic and the work needed to further our understanding of EVs to successfully deploy sEVs as a pain therapeutic.

Melt-Blown Polypropylene Membrane Modification for Enhanced Hydrophilicity.

Melt-blown, an environmentally friendly technique, is widely used to create high-quality non-woven fabrics by extruding molten polymer resins into interlaced fibers. In the realm of biomedical textiles, its unique microstructure makes it ideal for filtration and wound dressings. Our study focuses on modifying the surfaces of polypropylene melt-blown membranes. An effective, one-step, suitable, and reliable method to graft a bioactive polymer, sodium polystyrene sulfonate-PolyNaSS, onto the membranes has been developed. The process involves UV irradiation to initiate direct and progressive growth of NaSS over the surface through radical polymerization. To assess the efficiency of the grafting, techniques like colorimetry, water contact angle measurements, Fourier-transformed infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) were used. Outcomes related to the grafting were demonstrated by a change in wettability and quantitatively calculated sulfonate groups. Subsequently, grafted PolyNaSS promoted cell adhesion, as evidenced by improved cell morphology. On grafted membranes, fibroblasts exhibited a stretched shape, while non-grafted ones showed inactive round shapes. These findings underscore the chemical and biological reactivity of polypropylene materials, opening exciting possibilities for various applications of melt-blown materials.

Effect of peroxydisulfate activated by B-doped NiFe2Ox for degrading contaminants and mitigating nanofiltration membrane fouling in the landfill leachate treatment

Catalytic oxidation pretreatment is a significant focus in the field of membrane fouling control; however, traditional catalytic materials are plagued by limitations in catalytic sites and challenges in recovery. In this study, a novel catalyst, B-doped NiFe2Ox, was prepared with magnetic recovery capabilities and abundant oxygen vacancies to address landfill leachate treatment and mitigate membrane fouling. The results demonstrated the efficient activation of persulfate (PS) by the catalytic sites on B-NiFe2Ox, which significantly degraded the complex organic pollutants like conjugated double bonds and aromatic compounds in landfill leachate. A large amount of humic acid and soluble microbial products in the landfill leachate were efficiently degraded upon contact with sulfate and hydroxyl radicals produced by B-NiFe2Ox/PS, thereby resulting in achieving a chemical oxygen demand removal efficiency of up to 72% and more than a twofold enhancement in filtration flux. Moreover, the characteristics of the fouled layer reveal that the B-NiFe2Ox/PS system facilitated the formation of a porous cake layer, maximizing the retention of functional groups on the NF270 membrane surface. Notably, a minor presence of B-NiFe2Ox is uniformly distributed within the cake layer, indicating the in-situ occurrence of weak catalytic oxidation reactions. This study provides an effective and innovative approach utilizing catalytic oxidation for membrane fouling control.

Cm-p5, a molluscan-derived antifungal peptide exerts its activity by a membrane surface covering in a non-penetrating mode

Amidst the health crisis caused by the rise of multi-resistant pathogenic microorganisms, Antimicrobial Peptides (AMPs) have emerged as a potential alternative to traditional antibiotics. In this sense, Cm-p5 is an AMP with fungistatic activity against the yeast Candida albicans. Its antimicrobial activity and selectivity have been well characterized; however, the mechanism of action is still unknown. This study used biophysical approaches to gain insight into how this peptide exerts its activity. Stability and fluidity of lipid membrane were explored by liposome leakage and Laurdan generalized polarization (GP) respectively, suggesting that Cm-p5 does not perturb lipid membranes even at very high concentrations (≥100µm.L-1). Likewise, no depolarizing action was observed using 3,3'-propil-2,2'-thyodicarbocianine, a potential membrane fluorescent reporter, with C. albicans cells or the corresponding liposome models. Changes in liposome size were analyzed by Dynamic Light Scattering (DLS) data, indicating that Cm-p5 covers the vesicular surface slightly increasing liposome hydrodynamic size, without liposome rupture. These results were further corroborated with Langmuir monolayer isotherms, where no significant changes in lateral pressure or area per lipid were detected, indicating little or no insertion. Finally, data obtained from molecular dynamics simulations aligned with in vitro observations, whereby Cm-p5 slightly interacted with the fungal membrane model surface without causing significant perturbation. These results suggest Cm-p5 is not a pore-forming anti-fungal peptide and that other mechanisms of action on the membrane as some limitation of fungal nutrition or receptor-dependent transduction for depressing growth development should be explored.

Characterization and mitigation strategies for inorganic scaling in reverse osmosis system treating brackish groundwater

Water desalination has become a more effective and widespread technology for treating seawater and brackish water because of a shortage of freshwater resources in Morocco and the world. Reverse osmosis is a commonly used method for water desalination. Nevertheless, membrane fouling remains a serious problem facing this technique, including inorganic, organic, colloidal, and biofouling. This research aims to analyze the performance of reverse osmosis used on Souss Massa farm and solve the fouling issue by using the chemical and physical properties of feed, permeate, and reject water, thus the characterization of fouling deposited on the membrane. The fouling was characterized by several techniques, such as scanning electron microscopy coupled with energy dispersion X-ray spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The analysis revealed that Ca2+, Na+, Cl–, HCO3–, and SO42– are the most dominant ions in the feedwater. The predicting scaling indices and the characterization results of the scale structure developed on the membrane surface revealed that it was mainly composed of calcium carbonate and silica saturated. Changing the antiscalant and the proposed cleaning protocol prevent scale formation in reverse osmosis membranes and help increase and improve TDS's rejection rate from 94.23% to 97.04%.

Manuscript for: Journal of Environmental Chemical Engineering New insights into the influence of ultrafiltration pretreatment on reverse osmosis membrane fouling during urban sewage reclamation: Interaction between extracellular polymeric substances and inorganic foulants

Ultrafiltration (UF) has been frequently employed as pretreatment to mitigate reverse osmosis (RO) membrane fouling. The organic and inorganic substances outflowing from UF pretreatment collectively determine the subsequent RO membrane fouling behavior. However, most of the previous studies were focused on single organic compounds as well as CaSO4 scaling, yet complex organic matter such as extracellular polymeric substances (EPS) and various inorganic scaling (i.e. CaCO3, Ca3(PO4)2) coexisted during urban sewage reclamation. In this study, the impact of UF pretreatment on RO membrane fouling behavior, especially the interaction between EPS and CaCO3/Ca3(PO4)2 scaling, were systematically investigated. Results showed that the presence of UF significantly reduced the normalized flux decline (9.3% vs. 14.3%) and enhanced cleaning recovery efficiency (84.6% vs. 51.6%) of RO membrane, but increased scattered crystals (CaCO3 and Ca3(PO4)2) formation on RO membrane surface. Further investigation showed that the binding energy of the Ca2p1/2 and Ca2p3/2 peaks on fouled RO membrane exhibited a shift towards lower energy, which indicated a weak complexation between EPS and Ca2+, thereby increasing inorganic scaling and confirming the two-sides role of EPS retained by UF in RO membrane fouling. Moreover, static experiments indicated that EPS inhibited CaCO3 scaling rather than Ca3(PO4)2 scaling with the inhibition rates of 7.3% and 0.7%, respectively. To the best of our knowledge, it is the first to reveal the different effect of EPS on CaCO3 and Ca3(PO4)2 scaling. The results may provide a new insight into the effect of UF pretreatment on RO membrane fouling during urban sewage reclamation process.

The chondrogenic differentiation of BMSCs in collagen hydrogels and the effect of MMPs among cell-material interactions

The purpose of this study was to investigate the influence of the advanced structure of collagen on the chondrogenic differentiation of BMSCs encapsulated in collagen hydrogels, with an emphasis on MMPs which might affect the cell-material interactions. Collagen and gelatin-based hydrogels with comparable physicochemical properties but mainly distinctive in molecular structure were prepared and further utilized to load BMSCs to study the chondrogenesis. The detection results of MMPs in hydrogels with and without TIMP at both gene and protein levels suggested that MMPs were involved in cell recognition, adhesion, migration, proliferation and further remodeling of cell microenvironment. The chondrogenic gene detection, histological observation and extracellular matrix analysis indicated that the BMSCs were well differentiated into chondrocytes and maintained the phenotypes in collagen hydrogels (C group) which preserved the native structures, comparing with those results acquired from gelatin hydrogels (G group). Finally, the expression of several integrin subunits was investigated to analyze the connection of these cell membrane surface proteins and microenvironment remodeled by MMPs in collagen and gelatin hydrogels. The conclusion was drawn that the advanced structure of collagen affected the chondrogenesis of BMSCs via the cell-material interactions, among which MMPs were one of the major factors crucial to form appropriate microenvironment to modulate the BMSCs fate.Graphical abstract

Restoration of the Performance of Membranes Fouled and Wetted in a Pilot-scale Membrane Distillation Process

Objectives : The fouling and wetting of membranes in membrane distillation processes can significantly reduce membrane performance, thereby affecting overall process efficiency. The purpose of this study is to develop methods for restoring the performance of membranes used in a membrane distillation pilot plant operated in the Middle East by testing and optimizing various cleaning methods. This aims to maintain the long-term performance and improve the operational efficiency of the pilot plant through the reuse of restored membranes.Methods : To analyze the main fouling substances on the hollow fiber membranes collected from a module operated in a pilot plant, FTIR, XRD, and SEM analysis techniques were employed. A lab-scale module was fabricated using the collected membranes, and cleaning methods were applied. Citric acid was used for cleaning to restore membrane performance, which was evaluated by measuring water permeability and conductivity before and after cleaning.Results and Discussion : FTIR and XRD analyses revealed that the main fouling substances on the membranes used in the pilot plant were NaCl, CaCO<sub>3</sub>, and CaSO<sub>4</sub>. SEM and ICP analyses confirmed that the membranes near the feed inlet of the module experienced severer fouling compared to those near the outlet. The cleaning method involving pump circulation after inducing artificial wetting was found to be the most effective for restoring membrane performance. Notably, when a high concentration of citric acid was used, almost all fouling substances on the membrane surface were removed, restoring membrane performance to nearly its original state.Conclusion : The cleaning method involving artificial wetting followed by pump circulation was determined to be the optimal method for successfully restoring the performance of membranes fouled and wetted in membrane distillation processes.

Improving ultrafiltration efficiency of acidified skim milk using bipolar membrane electrodialysis: Impact on protein concentrate composition, process performance, and fouling

The efficiency of ultrafiltration (UF) of acidified skim milk (SM) is impaired by protein aggregation and mineral scaling. The aim of this study is to assess the potential of acidification by electrodialysis with bipolar membranes (EDBM), in comparison with citric acid (CA), prior to the UF process on filtration performance, fouling and composition of the protein concentrates. Electro-acidification, facilitated by a water-splitting reaction, decreased the pH of milk to ∼ 5.7 and caused partial demineralization (∼21.9 % ash removal), which increased protein concentration and reduced UF fouling. This resulted in a ∼ 34.7 % increase in average permeate flux and ∼ 9.5 % more efficient removal of calcium from the UF retentates compared to CA. The final ash content of the produced protein concentrates showed that the EDBM acidification resulted in an ash content of 5.76 ± 0.23 % on a dry basis, while the citric acid method resulted in an ash content of 6.63 ± 0.27 %, showing a reduction of ∼ 13.1 %. Additionally, electro-chemical and spectroscopic methods were employed to evaluate the ion-exchange membranes (IEMs). Minor changes were observed in the specific resistivity and permselectivity of the cation-exchange membranes (CMs), indicating the formation of fouling and inorganic scaling precipitates on the membrane surface due to the process. The FTIR analysis of both CMs and bipolar membranes (BMs) showed sorption of proteins on the surface. The FTIR and atomic force microscopy (AFM) results of UF membranes confirmed that acidification using CA led to increased fouling and reduced permeate flux, attributed to the aggregation of proteins and lipid residues compared to the EDBM acidification method. This study provides valuable insights into improving and enhancing UF performance while significantly reducing membrane fouling during the filtration of partially acidified dairy streams, by employing chemical-free green technologies.

Metal-organic framework membranes with scale-like structure for efficient propylene/propane separation

The fabrication of metal-organic framework (MOF) membranes with high propylene/propane selectivity, high mechanical endurance and ease of scaling up always remains a challenge. Inspired by the ubiquitous biological wear-resistant structure, here we show ZIF-67 membranes with a tangential-normal interlaced structure (TN-ZIF-67) for one-step acquisition of polymer-grade propylene, which is endowed with the merits of intergranular defect elimination, partial ZIF-67 lattice flexibility restriction and anti-wear of the membrane surface. The TN-ZIF-67 membrane exhibits an optimal propylene/propane mixture separation factor of 221, and the separation performance remained unchanged after 1.5 years of storage or abrasion by repeated sanding. The distinctive membrane structure can be further scaled up on 4 mm-diameter tubular substrates. This work demonstrates a strategy to extend the rational design of defect-free, anti-wear MOF membranes with superior separation performance and stability that could fulfill future industrial applications.