Membranes

In this study, ultrafiltration membranes were developed via a nonsolvent-induced phase separation method for the removal of asphaltenes from crude oil. Polyacrylonitrile (PAN) and acrylonitrile copolymers with acrylic acid were used as membrane materials. Copolymerizing acrylonitrile with acrylic acid resulted in an improvement in the fouling resistance of the membranes. The addition of 10% of acrylic acid to the polymer chain decreases the water contact angle from 71° to 43°, reducing both the total fouling and irreversible fouling compared to membranes made from a PAN homopolymer. The obtained membranes with a pore size of 32–55 nm demonstrated a pure toluene permeance of 84.8–130.4 L/(m²·h·bar) and asphaltene rejection from oil/toluene solutions (100 g/L) of 33–95%. An analysis of the asphaltene rejection values revealed that the addition of acrylic acid increases the rejection values in comparison to PAN membranes with the same pore size. Our results suggest that the acrylonitrile–acrylic acid copolymer ultrafiltration membranes have promising potential for the efficient removal of asphaltenes from crude oil. Full article

In order to enhance the separation performance and reduce the heat loss of transmembrane for membrane distillation, the thermal efficiency and hydrophobicity of the membrane distillation need to be simultaneously enhanced. In this work, a polyvinylidene difluoride/polyethylene glycol terephthalate (PVDF/PET) hydrophobic/hydrophilic membrane has been prepared by non-solvent phase induction method. Nanosized silica aerogel (SiAG) with high porosity has been added to the composite membranes. The modifying effects and operating conditions on permeate flux and thermal efficiency in direct contact membrane distillation (DCMD) are investigated. Furthermore, the latent heat of vaporization and the heat transfer across the membranes have been compared for SiAG addition, which indicates that the composite PVDF@SiAG/PET membranes demonstrate a great potential for distillation-separation application due to their high heat efficiency. Full article

Applying edible coatings added with plant essential oils is a strategy used to delay ripening processes in climacteric fruits such as papaya. Formulations comprising 3% or 4% cassava starch (w/v), added with clove or cinnamon essential oils (2 mL/L), were tested for microbial inhibition (in vitro) purposes. Moreover, these fruits’ physicochemical and microbiological aspects were assessed at 25 °C, for 12 days. Slight variations in pH and Brix values were observed during storage. On the other hand, there were no significant variations in carotenoid contents over storage time. The papaya fruits’ coating contributed to reducing their weight loss from 40.66% (uncoated sample) to 24.10% on the 12th storage day, as well as delayed changes often observed during the ripening process. The 4% cassava starch coatings added with essential oils were more efficient in reducing microbiological levels. The herein proposed treatments reduced aerobic mesophilic bacteria, as well as molds and yeast counts, by 1.48 and 1.95 log CFU/g, on average, respectively, in comparison to the control sample. The assessed microorganism counts were higher in the uncoated sample than in the coated papaya fruits, after 12 days of storage. Thus, the tested coatings can potentially delay the emergence of post-harvest changes; consequently, they can help improve the quality of papaya fruits and extend their shelf life. Full article

Several chromatographic approaches have been established over the last decades for the production of pharmaceutically relevant viruses. Due to the large size of these products compared to other biopharmaceuticals, e.g., proteins, convective flow media have proven to be superior to bead-based resins in terms of process productivity and column capacity. One representative of such convective flow materials is membranes, which can be modified to suit the particular operating principle and are also suitable for economical single-use applications. Among the different membrane variants, affinity surfaces allow for the most selective separation of the target molecule from other components in the feed solution, especially from host cell-derived DNA and proteins. A successful membrane affinity chromatography, however, requires the identification and implementation of ligands, which can be applied economically while at the same time being stable during the process and non-toxic in the case of any leaching. This review summarizes the current evaluation of membrane-based affinity purifications for viruses and virus-like particles, including traditional resin and monolith approaches and the advantages of membrane applications. An overview of potential affinity ligands is given, as well as considerations of suitable affinity platform technologies, e.g., for different virus serotypes, including a description of processes using pseudo-affinity matrices, such as sulfated cellulose membrane adsorbers. Full article

In this paper, a cobalt (Co)-chelated polynaphthalene imine (Co-PNIM) was calcined to become an oxygen reduction reaction (ORR) electrocatalyst (Co-N-C) as the cathode catalyst (CC) of an anion exchange membrane fuel cell (AEMFC). The X-ray diffraction pattern of CoNC-1000A900 illustrated that the carbon matrix develops clear C(002) and Co(111) planes after calcination, which was confirmed using high-resolution TEM pictures. Co-N-Cs also demonstrated a significant ORR peak at 0.8 V in a C–V (current vs. voltage) curve and produced an extremely limited reduction current density (5.46 mA cm⁻²) comparable to commercial Pt/C catalysts (5.26 mA cm⁻²). The measured halfway potential of Co-N-C (0.82 V) was even higher than that of Pt/C (0.81 V). The maximum power density (P_max) of the AEM single cell upon applying Co-N-C as the CC was 243 mW cm⁻², only slightly lower than that of Pt/C (280 mW cm⁻²). The Tafel slope of CoNC-1000A900 (33.3 mV dec⁻¹) was lower than that of Pt/C (43.3 mV dec⁻¹). The limited reduction current density only decayed by 7.9% for CoNC-1000A900, compared to 22.7% for Pt/C, after 10,000 redox cycles. Full article

Recent experimental work has shown zeolite membrane-based separation as a promising potential technology for Kr/Xe gas mixtures due to its much lower energy requirements in comparison to cryogenic distillation, the conventional separation method for such mixtures. Such a separation is also economically rewarding because Xe is in high demand, as a valuable product for many applications/processes. In this work, we have used Molecular Dynamics (MD) simulations to study the effects of different conditions, i.e., temperature, pressure, and gas feed composition, on Kr/Xe separation performance via DD3R zeolite membranes. We provide a comprehensive study of the permeation of the different gas species, density profiles, and diffusion coefficients. Molecular simulations show that if the feed is changed from pure Kr/Xe to an equimolar mixture, the Kr/Xe separation factor increases, which agrees with experiments. In addition, when Ar is introduced as a sweep gas, the adsorption of both Kr and Xe increases, while the permeation of pure Kr increases. A similar behavior is observed with equimolar mixtures of Kr/Xe with Ar as the sweep gas. High-separation Kr/Xe selectivity is observed at 50 atm and 425 K but with low total permeation rates. Changing pressure and temperature are found to have profound effects on optimizing the separation selectivity and the permeation throughput. Full article

The aim of this paper was to determine the emulsification properties of protein aggregates obtained from heat pretreated yellow field pea protein concentrate (PPC). PPC dispersions were prepared in distilled water (adjusted to pH 3.0, 5.0, 7.0, or 9.0), heated in a water bath (100 °C) for 30 min, centrifuged and the supernatant passed first through a 30 kDa membrane and, then, the first retentate (>30 kDa) through a 50 kDa membrane. The 50 kDa membrane separation yielded a second retentate (>50 kDa proteins), which was isolated for emulsification studies. The near UV circular dichroic spectra of the protein samples showed more unfolded structures at pH 3.0 and 5.0 than at pH 7.0 and 9.0. The presence of small and spherical oil droplets of emulsions stabilized by the >50 kDa proteins at pH 3.0, 7.0, and 9.0 was confirmed by confocal laser scanning microscopy images. Emulsions stabilized at pH 7.0 and 9.0 had a narrower size distribution range than at pH 3.0 and 5.0. A narrow oil droplet size distribution range and lower interfacial protein concentrations of the emulsions stabilized by the >50 kDa proteins were observed at the corresponding pH of the heat treatment when compared to other pH values. Emulsions stabilized by the >50 kDa proteins exhibited a relatively low flocculation and coalescence index, which infers relative stability. The results from this work suggest that heat pretreatment of the PPC led to the formation of new protein aggregates, especially FT9 with enhanced emulsification properties, at some of the test conditions when compared to the unheated PPC. Full article

Ionic polymer membranes have not yet gained widespread practical application in areas such as water purification and energy harvesting due to their high cost and tendency to swell. The present study involved the fabrication of reinforced textile structures composed of polytetrafluoroethylene (PTFE)-reinforced Nafion membranes coated with non-precious metals, copper and silver, as a surface electrode by applying a chemical decomposition technique. Several mechanical, contact angle measurement and dielectric tests were conducted on membranes to evaluate their mechanical, wettability and conductivity properties. From scanning electron microscopy, it is clear that the formation of surface electrodes with uniform dispersion of metal particles. Scratch test reveals the adhesive strength between the coated metal particles and membrane. The silver-activated copper-coated membrane has a high contact angle of 121°. Thus, the fabricated membranes can have good antibacterial and adsorption properties for water treatment. The copper-coated membrane has a high Young’s modulus of 779 ± 80 MPa and a tensile strength of 29.1 ± 8 MPa, whereas the elongation at break is more for silver-activated copper-coated samples recorded as 158 ± 4%. The viscoelastic behavior of the membranes was analyzed through dynamic mechanical analysis (DMA). A sharp rise in the storage modulus (E′) value of 4.8 × 10¹⁰ Pa at ~80 °C at a frequency of 1 Hz on metal surface electrodes signifies an improvement in the strength of the material in comparison to the initial pure membrane. The successful enhancement of conductivity on the membrane surface via chemical deposition on the silver-activated membrane is 1 × 10⁻⁴ (S/cm) and holds great potential for facilitating voltage transmission through the tribolayer in the nanogenerators. Full article

Although only a slightly radioactive element, thorium is considered extremely toxic because its various species, which reach the environment, can constitute an important problem for the health of the population. The present paper aims to expand the possibilities of using membrane processes in the removal, recovery and recycling of thorium from industrial residues reaching municipal waste-processing platforms. The paper includes a short introduction on the interest shown in this element, a weak radioactive metal, followed by highlighting some common (domestic) uses. In a distinct but concise section, the bio-medical impact of thorium is presented. The classic technologies for obtaining thorium are concentrated in a single schema, and the speciation of thorium is presented with an emphasis on the formation of hydroxo-complexes and complexes with common organic reagents. The determination of thorium is highlighted on the basis of its radioactivity, but especially through methods that call for extraction followed by an established electrochemical, spectral or chromatographic method. Membrane processes are presented based on the electrochemical potential difference, including barro-membrane processes, electrodialysis, liquid membranes and hybrid processes. A separate sub-chapter is devoted to proposals and recommendations for the use of membranes in order to achieve some progress in urban mining for the valorization of thorium. Full article

Plasmalogens are a unique family of cellular glycerophospholipids that contain a vinyl-ether bond. The synthesis of plasmalogens is initiated in peroxisomes and completed in the endoplasmic reticulum. Plasmalogens are transported to the post-Golgi compartment, including endosomes and plasma membranes, in a manner dependent on ATP, but not vesicular transport. Plasmalogens are preferentially localized in the inner leaflet of the plasma membrane in a manner dependent on P4-type ATPase ATP8B2, that associates with the CDC50 subunit. Plasmalogen biosynthesis is spatiotemporally regulated by a feedback mechanism that senses the amount of plasmalogens in the inner leaflet of the plasma membrane and controls the stability of fatty acyl-CoA reductase 1 (FAR1), the rate-limiting enzyme for plasmalogen biosynthesis. The physiological consequences of such asymmetric localization and homeostasis of plasmalogens are discussed in this review. Full article

The cells of living organisms are surrounded by the biological membranes that form a barrier between the internal and external environment of the cells. Cell membranes serve as barriers and gatekeepers. They protect cells against the entry of undesirable substances and are the first line of interaction with foreign particles. Therefore, it is very important to understand how substances such as particulate matter (PM) interact with cell membranes. To investigate the effect of PM on the electrical properties of biological membranes, a series of experiments using a black lipid membrane (BLM) technique were performed. L-α-Phosphatidylcholine from soybean (azolectin) was used to create lipid bilayers. PM samples of different diameters (<4 (SRM-PM4.0) and <10 μm (SRM-PM10) were purchased from The National Institute of Standards and Technology (USA) to ensure the repeatability of the measurements. Lipid membranes with incorporated gramicidin A (5 pg/mL) ion channels were used to investigate the effect of PM on ion transport. The ionic current passing through the azolectin membranes was measured in ionic gradients (50/150 mM KCl on cis/trans side). In parallel, the electric membrane capacitance measurements, analysis of the conductance and reversal potential were performed. Our results have shown that PM at concentration range from 10 to 150 μg/mL reduced the basal ionic current at negative potentials while increased it at positive ones, indicating the interaction between lipids forming the membrane and PM. Additionally, PM decreased the gramicidin A channel activity. At the same time, the amplitude of channel openings as well as single channel conductance and reversal potential remained unchanged. Lastly, particulate matter at a concentration of 150 μg/mL did not affect the electric membrane capacity to any significant extent. Understanding the interaction between PM and biological membranes could aid in the search for effective cytoprotective strategies. Perhaps, by the use of an artificial system, we will learn to support the consequences of PM-induced damage. Full article

An extracorporeal blood purification method called continuous renal replacement therapy uses a porous hollow-fiber polymeric membrane that is exposed to prolonged contact with blood. In that condition, like with any other submerged filtration membrane, the hemofilter loses its properties over time and use resulting in a rapid decline in flux. The most significant reason for this loss is the formation of a biofilm. Protein, blood cells and bacterial cells attach to the membrane surface in complex and fluctuating processes. Anticoagulation allows for longer patency of vascular access and a longer lifespan of the membrane. Other preventive measures include the modification of the membrane itself. In this article, we focused on the role of nanoadditives in the mitigation of biofouling. Nanoparticles such as graphene, carbon nanotubes, and silica effectively change surface properties towards more hydrophilic, affect pore size and distribution, decrease protein adsorption and damage bacteria cells. As a result, membranes modified with nanoparticles show better flow parameters, longer lifespan and increased hemocompatibility. Full article

In this study, a polyacrylonitrile nanofiber membrane was first hydrolyzed and then functionalized with tris(hydroxymethyl)aminomethane (P-Tris), then used as an affinity nanofiber membrane for lysozyme adsorption in membrane chromatography. The dynamic adsorption behavior of lysozyme was investigated in a flow system under various operating parameters, including adsorption pHs, initial feed lysozyme concentration, loading flow rate, and the number of stacked membrane layers. Four different kinetic models, pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion kinetic models, were applied to experimental data from breakthrough curves of lysozyme. The results showed that the dynamic adsorption results were fitted well with the pseudo-second-order kinetic model. The breakthrough curve experimental results show significant differences in the breakthrough time, the dynamic binding capacity, the length of the mass transfer zone, and the utilization rate of the membrane bed under different operating parameters. Four dynamic adsorption models (i.e., Bohart–Adams, Thomas, Yoon–Nelson, and BDST models) were used to analyze the breakthrough curve characteristics of the dynamic adsorption experiments. Among them, the Yoon–Nelson model was the best model to fit the breakthrough curve. However, some of the theoretical results based on the Thomas and Bohart–Adams model analyses of the breakthrough curve fit well with the experimental data, with an error percentage of <5%. The Bohart–Adams model has the largest difference from the experimental results; hence it is not suitable for breakthrough curve analysis. These results significantly impact dynamic kinetics studies and breakthrough curve characteristic analysis in membrane bed chromatography. Full article

Membrane fouling is an inevitable obstacle of polyamide composite forward osmosis (FO) membranes in oily wastewater treatment. In this study, zwitterionic arginine (Arg) is grafted onto nascent self-made FO polyamide poly(ether sulfone) (PA-PES) membrane, imparting superior hydrophilic, antifouling, and antibacterial properties to the membrane. Detailed characterizations revealed that the Arg-modified (Arg-PES) membrane presented obviously surface positively charged and unique morphology. Results showed that our strategy endowed the optimized membrane, the water flux increased by 113.2% compared to the pristine membrane, respectively, meanwhile keeping high NaCl rejection > 93.9% (with DI water as feed solution and 0.5 M NaCl as draw solution, FO mode). The dynamic fouling tests indicated that the Arg-PES membranes exhibited much improved antifouling performance towards oily wastewater treatment. The flux recovery ratios of the membrane were as high as 92.0% for cationic emulsified oil (cetyl pyridinium chloride, CPC), 87.0% for neutral emulsified oil (Tween-80), and 86.0% for anionic emulsified oil (sodium dodecyl sulfate, SDS) after washing, respectively. Meanwhile, the Arg-PES membranes assembled with guanidine cationic groups exhibited an enhanced antibacterial property against E. coli, which exhibited a high antibacterial efficiency of approximately 96%. Consequently, the newly arginine functionalized FO membrane possesses impressive antifouling performance, while simultaneously resisting bacterial invasion, thus rendering it an ideal alternative for oily wastewater treatment in the FO process. Full article

Polysulfone (PSf) membranes typically have a negligible rejection of salts due to the intrinsic larger pore size and wide pore size distribution. In this work, a facile and scalable heat treatment was proposed to increase the salt rejection. The influence of heat treatment on the structure and performance of PSf membranes was systematically investigated. The average pore size decreased from 9.94 ± 5.5 nm for pristine membranes to 1.18 ± 0.19 nm with the increase in temperature to 50 °C, while the corresponding porosity decreased from 2.07% to 0.13%. Meanwhile, the thickness of the sponge structure decreased from 20.20 to 11.5 μm as the heat treatment temperature increased to 50 °C. The MWCO of PSf decreased from 290,000 Da to 120 Da, whereas the membrane pore size decreased from 5.5 to 0.19 nm. Correspondingly, the water flux decreased from 1545 to 27.24 L·m⁻²·h⁻¹, while the rejection ratio increased from 3.1% to 74.0% for Na₂SO₄, from 1.3% to 48.2% for MgSO₄, and from 0.6% to 23.8% for NaCl. Meanwhile, mechanism analysis indicated that the water evaporation in the membranes resulted in the shrinkage of the membrane pores and decrease in the average pore size, thus improving the separation performance. In addition, the desalting performance of the heat-treated membranes for real actual industrial wastewater was improved. This provides a facile and scalable route for PSf membrane applications for enhanced desalination. Full article

Chitosan (CS), a promising potential biopolymer with exquisite biocompatibility, economic viability, hydrophilicity, and chemical modifications, has drawn interest as an alternative material for proton exchange membrane (PEM) fabrication. However, CS in its original form exhibited low proton conductivity and mechanical stability, restricting its usage in PEM development. In this work, chitosan was functionalized (sulfonic acid (-SO₃H) groups)) to enhance proton conductivity. The sulfonated chitosan (sCS) was blended with polyvinylidene fluoride (PVDF) polymer, along with the incorporation of functionalized SiO₂ (–OH groups), for fabricating chitosan-based composite proton exchange membranes to enhance microbial fuel cell (MFC) performances. The results show that adding functionalized inorganic fillers (fSiO₂) into the membrane enhances the mechanical, thermal, and anti-biofouling behavior. From the results, the PVDF/sCS/fSiO₂ composite membrane exhibited enhanced proton conductivity 1.0644 × 10⁻² S cm⁻¹ at room temperature and increased IEC and mechanical and chemical stability. Furthermore, this study presents a revolutionary way to generate environmentally friendly natural polymer-based membrane materials for developing PEM candidates for enhanced MFC performances in generating bioelectricity and wastewater treatment. Full article

The membrane process has a limit to the decay of various pollutants in water. To improve the problem, the roles of backwashing media and titanium dioxide (TiO₂) photocatalyst-immobilized-polyethersulfone (PES) beads’ concentration were investigated in a combined system of tubular alumina MF and the PES beads for advanced drinking water treatment. The space between the outside of the MF membrane and the module inside was filled with the PES beads. UV at a wavelength of 352 nm was irradiated from outside of the acryl module. A quantity of humic acid and kaolin was dissolved in distilled water for synthetic water. Water or air intermittent backwashing was performed outside to inside. The membrane fouling resistance after 3 h process (R_f,180) was minimum at 30 g/L of the PES beads for water backwashing, and at 40 g/L for air backwashing when increasing the PES beads from 0 to 50 g/L. The irreversible membrane fouling resistance after physical cleaning (R_if) was at the bottom at 5 g/L of the PES beads for water backwashing, which was 3.43 times higher than minimal at 40 g/L of the PES beads for air backwashing. The treatment effectiveness of turbidity increased when increasing the PES beads’ concentration from 0 to 50 g/L; however, it reached a maximum at 98.1% at 40 g/L and 99.2% at 50 g/L for water and air backwashing, respectively. The treatment effectiveness of UV₂₅₄ absorbance, which was dissolved organic matter (DOM), increased dramatically when increasing the PES beads; however, it reached a peak of 83.0% at 40 g/L and 86.0% at 50 g/L for water and air backwashing, respectively. Finally, the best PES beads’ concentration was 20~30 g/L to minimize the membrane fouling; however, it was 50 g/L to remove pollutants effectively. The water backwashing was better than the air at treating DOM; however, the air backwashing was more effective than the water at removing turbid matter and reducing membrane fouling. Full article