Porous Membrane Research Articles

Fouling-resistant superhydrophobic polyketone membranes modified with fluorine-containing silica for water-in-oil emulsion separation

Membranes for water-in-oil (W/O) emulsion separation require high emulsion permeance, oil purity selectivity, high water-fouling resistance, and reusability. Therefore, a functional membrane structure that satisfies these needs is required. Herein, we describe the effective modification of a membrane surface by forming functional silica particles on a porous polyketone (PK) membrane to form a hierarchical membrane structure with enhanced roughness and superhydrophobicity. We also demonstrate the potential application of the membrane for W/O emulsion separation based on enhanced performance and fouling resistance. Membranes were fabricated by forming silica particles on a porous PK membrane by a sol–gel method using tetraethoxysilane (TEOS). By modifying these silica particles with fluoroalkyl silane (FAS), a superhydrophobic membrane with a high contact angle of up to 162° was fabricated. The resulting FAS-modified membrane had higher permeance with regard to a toluene W/O emulsion than an unmodified PK membrane or a commercially available polyvinylidene fluoride (PVDF) membrane. It was possible to recycle the FAS-modified membrane by simply washing it in toluene to remove external fouling. This effective membrane surface modification helps to enhance both emulsion permeance and fouling resistance during W/O emulsion separation.

High throughput PTFE@PPS /ACFs porous membrane for continuous highly effective oil-water separation

We proposed a feasible and straightforward approach for fabricating a superhydrophobic polytetrafluoroethylene coated polyphenylene sulfide/aramid composite film (PTFE@PPS/ACFs porous membrane) for oil-water separation. This process involves utilizing a wet paper making process combined with a spray coating technique. The PPS/ACFs composite membrane displays a three-dimensional network structure by the application of wet papermaking approach. The uniformly spray coating of PTFE on its surface results in a superhydrophobic PTFE@PPS/ACFs porous membrane (PPAM). The membrane obtained through this method can effectively separate oil and water. It is remarkable in separating oil-water lotion stabilized by surfactant, achieving a separation efficiency of up to 99.9 % with a high flux of 8000 L/m2·h−1. Additionally, owing to the inherent thermal stability of the membrane, the PPAM is recyclable. In summary, the PTFE@PPS/ACFs porous membrane is a promising for separating various oil-water emulsions. Its outstanding performance, including high separation efficiency, flux, and recyclability, underscores its potential for practical applications for oil-water separation.

Microfiltration Membrane Pore Functionalization with Primary and Quaternary Amines for PFAS Remediation: Capture, Regeneration, and Reuse.

The widespread production and use of multi-fluorinated carbon-based substances for a variety of purposes has contributed to the contamination of the global water supply in recent decades. Conventional wastewater treatment can reduce contaminants to acceptable levels, but the concentrated retentate stream is still a burden to the environment. A selective anion-exchange membrane capable of capture and controlled release could further concentrate necessary contaminants, making their eventual degradation or long-term storage easier. To this end, commercial microfiltration membranes were modified using pore functionalization to incorporate an anion-exchange moiety within the membrane matrix. This functionalization was performed with primary and quaternary amine-containing polymer networks ranging from weak to strong basic residues. Membrane loading ranged from 0.22 to 0.85 mmol/g membrane and 0.97 to 3.4 mmol/g membrane for quaternary and primary functionalization, respectively. Modified membranes exhibited a range of water permeances within approximately 45-131 LMH/bar. The removal of PFASs from aqueous streams was analyzed for both "long-chain" and "short-chain" analytes, perfluorooctanoic acid and perfluorobutyric acid, respectively. Synthesized membranes demonstrated as high as 90% rejection of perfluorooctanoic acid and 50-80% rejection of perfluorobutyric acid after 30% permeate recovery. Regenerated membranes maintained the capture performance for three cycles of continuous operation. The efficiency of capture and reuse can be improved through the consideration of charge density, water flux, and influent contaminant concentration. This process is not limited by the substrate and, thus, is able to be implemented on other platforms. This research advances a versatile membrane platform for environmentally relevant applications that seek to help increase the global availability of safe drinking water.

All-in-one fabrication of NiO nanorods/carbon-containing porous catalytic polymer membranes for persulfate-facilitated oxidation-adsorption of diclofenac in flow–through

We introduce a novel all-in-one fabrication method for porous catalytic polyethersulfone (PES) membranes containing NiO nanorods and carbon nanoparticles. This method is based on the sonochemical in situ solidification of a metal salt with NaBH4 in presence of carbon particles in a PES-containing casting-reaction solution, directly followed by membrane preparation via film casting cum phase separation. In the catalytic flow-through degradation of 20 mg/L aqueous diclofenac with persulfate as oxidant, an as-prepared NiO-carbon-PES membrane achieved a 99 % aromatic content removal degree at a residence time of only 1.6 s. In comparison, NiO and CuO membranes without carbon particles exhibited < 40 % aromatic removal degrees. The high performance was attributed to a degradation-induced adsorption, with a diclofenac removal capacity of 950 mg/g of incorporated carbon particles. We demonstrated that diclofenac is catalytically mineralized in the membrane at incorporated NiO nanorods, followed by adsorption of remaining degradation products at nearby carbon particles. Our data further suggests that reducing NiO to Ni(0) via a membrane pretreatment shifts the catalytic persulfate activation from a radicaltoa non-radical pathway, and that HCO3– can function as sacrificial electron donor for Ni(0). This completely mitigated nickel leaching from the membrane in contact to persulfate. Moreover, even in the presence of NaHCO3 and NaCl, a Ni(0)–carbon–PES membrane consistently eliminated ∼ 90 % of the total organic carbon (TOC) from a 2 mg/L diclofenac feed containing persulfate in single-pass flow-through mode (continuously for 5 h, respectively for 500 L/m2 permeate volume), with no detectable release of degradation products or any nickel leaching.

Partitioning of proteins and small molecular weight compounds from alfalfa juice during ultrafiltration

Ribulose-1,5-biphosphate-carboxylase/oxygenase (RuBisCO) from alfalfa is a promising source of alternative food protein, but it is challenging to purify. Ultrafiltration shows potential for concentrating and fractionating RuBisCO from low molecular weight compounds present in the extracted juice, but there is limited information on their partitioning depending on the membrane pore size. Therefore, the objective of this study was to evaluate the partitioning of various compounds from the juice depending on membrane pore size. It was hypothesized that both membrane pore sizes will retain RuBisCO but might partition low molecular weight compounds within the matrix differently. RuBisCO was fully retained by both the 300 and 100 kDa polyethersulfone (PES) membranes, while ash (29.7%–35.4% dry matter (DM)), non-protein nitrogen (2.38%–2.53% DM), and free N-terminals (10.13–10.34 mg glutamic equivalent/100 mg DM) were transmitted through both membranes. The retentates showed a distinct yellow color when filtering with 100 kDa membranes, but not when using 300 kDa membranes. Although no significant differences in total polyphenol permeation were observed through a spectrophotometric assay, a metabolomics screening analysis showed that the 100 kDa membranes had less transmission of the flavonoids apigenin, chrysoeriol, tricin, and tricin glycosides, which might contribute to the yellow color. These results reiterate the importance of measuring individual polyphenols using hyphenated techniques as opposed to spectrophotometric total reducing capacity. Sixteen saponins were identified and their permeation was lower in the 100 than the 300 kDa membranes, indicating a better potential for higher degree of protein refinement for the latter. This study demonstrates for the first time the difference in partitioning of the small molecular weight components, using PES membranes of similar chemistry but different size, during ultrafiltration of alfalfa juice.

Asymmetric porous polybenzimidazole membrane with tunable morphology for vanadium flow battery (VFB)

Polybenzimidazole (PBI) membranes have attracted much attention for flow batteries due to their good chemical stability. However, the high area resistance (AR) of dense PBI limits its further development in VFBs. Herein, we design a sintering method to remove the phthalates with different molecular structures in the ternary system (PBI as polymer, N-methylpyrrolidone as solvent, and phthalates as non-solvent). Asymmetric PBI membranes with adjustable and disconnected pores, as well as ultrathin-dense layers, are prepared. This series of porous membranes shows excellent overall performance in VFBs. Among them, the porous NPBI-DBP-200 membrane (0.139 Ω cm2) with DBP as the non-solvent exhibits a lower AR compared to the dense NPBI (0.489 Ω cm2). At a current density of 200 mA cm−2, the energy efficiency (EE) of a single cell assembled with the NPBI-DBP-200 membrane (EE = 78.26 %) has improved by 26.37 % compared to the dense NPBI membrane (EE = 61.93 %). In addition, the porous NPBI-DBP-200 membrane has excellent in-situ stability, and the single cell can operate stably for 1800 cycles at the current density of 120 mA cm−2. This work presents a novel, easy-to-use technique for preparing high-performance porous PBI membranes with adjustable pore morphology.

Uncovering the membrane and pore formation mechanisms of the lysozyme membrane made via the amyloid-like assembly

Biomimetic protein membranes have attracted increasing interests because of their distinctive separation properties in the membrane field. Low-cost and stable protein lysozyme has been intensively invetigated to fabricate high-performance sepration membranes via a facile and scalable method of amyloid-like assembly. However, the pore formation mechnism of the lysozyme membrane remains unclear. Herein, the lysozyme membranes were fabricated and the membrane formation mechnism and separation properties were investigated experimentally. Molecular dynamics simulation (MDS) was also employed to reveal the pore formation mechanism of the lysozyme membrane. The fabricated lysozyme membrane achieved a stable high water permeance of 10.2 L m−2 h−1 bar−1, as well as a relatively high separation factor (9.5) towards antibiotic and sodium chloride. MDS results found that the membrane pore size is governed by the amino acid compositions and is negatively dependent on the intermolecular forces among amino acids around the pores. Selective pores with 0.54 nm in diameter are primarily formed by these amino acids including alanine (35 %), aspartic acid (25 %), arginine (15 %), phenylalanine (11 %), and lysine (7 %), in which half of them have hydrophobic side chains with no charge, and another half have hydrophilic side chains with balanced charges. This work may stimulate the development of highly permeable and selective protein membranes by carefully engineering their amino acid compositions with optimal charges and hydrophobicity for generation of numerous selective pores.

A flexible strategy to fabricate trumpet-shaped porous PDMS membranes for organ-on-chip application.

Porous polydimethylsiloxane (PDMS) membrane is a crucial element in organs-on-chips fabrication, supplying a unique substrate that can be used for the generation of tissue-tissue interfaces, separate co-culture, biomimetic stretch application, etc. However, the existing methods of through-hole PDMS membrane production are largely limited by labor-consuming processes and/or expensive equipment. Here, we propose an accessible and low-cost strategy to fabricate through-hole PDMS membranes with good controllability, which is performed via combining wet-etching and spin-coating processes. The porous membrane is obtained by spin-coating OS-20 diluted PDMS on an etched glass template with a columnar array structure. The pore size and thickness of the PDMS membrane can be adjusted flexibly via optimizing the template structure and spinning speed. In particular, compared to the traditional vertical through-hole structure of porous membranes, the membranes prepared by this method feature a trumpet-shaped structure, which allows for the generation of some unique bionic structures on organs-on-chips. When the trumpet-shape faces upward, the endothelium spreads at the bottom of the porous membrane, and intestinal cells form a villous structure, achieving the same effect as traditional methods. Conversely, when the trumpet-shape faces downward, intestinal cells spontaneously form a crypt-like structure, which is challenging to achieve with other methods. The proposed approach is simple, flexible with good reproducibility, and low-cost, which provides a new way to facilitate the building of multifunctional organ-on-chip systems and accelerate their translational applications.

Membrane tension evolution and mechanical regulation of melittin-induced membrane poration

Abstract Membrane tension plays a crucial role in various fundamental cellular processes, with one notable example being the T cell-mediated elimination of tumor cells through perforin-induced membrane perforation by amplifying cellular force. However, the mechanisms governing the regulation of biomolecular activities at the cell interface by membrane tension remain elusive. In this study, we investigated the correlation between membrane tension and poration activity of melittin, a prototypical pore-forming peptide, using dynamic giant unilamellar vesicle leakage assays combined with flickering tension analysis, molecular dynamics simulations, and live cell assays. The results demonstrate that an increase in membrane tension enhances the activity of melittin, particularly near its critical pore-forming concentration. Moreover, peptide actions such as binding, insertion, and aggregation in the membrane further influence the evolution of membrane tension. Live cell experiments reveal that artificially enhancing membrane tension effectively enhances melittin’s ability to induce pore formation and disrupt membranes, resulting in up to a ten-fold increase in A549 cell mortality when exposed to a concentration of 2.0-μg⋅mL−1 melittin. Our findings elucidate the relationship between membrane tension and the mechanism of action as well as pore-forming efficiency of melittin, while providing a practical mechanical approach for regulating functional activity of molecules at the cell-membrane interface.

High frequency venting of MEMS ultrasonic transducers and sensors: materials solutions.

Abstract This paper introduces the concept of ultrasonic venting. Similar to acoustic vents, ultrasonic vents refer to the aperture in air-coupled MEMS ultrasonic transducers (either PMUT or CMUT) intended to allow the equalization of internal and external pressures, the transfer of heat and the pass of ultrasonic waves, while impeding the penetration of fluids or particles that can affect the transducer membrane. To that end, vents are covered with a porous membrane whose properties are tuned to meet the afore mentioned requirements. The main difficulty in ultrasonic venting, compared with acoustic venting, is that the required “transparency” to ultrasonic waves is much more difficult to achieve. This involves two main problems as both transmission loss and frequency distortion are much larger at ultrasonic frequencies than in the audio range. The objectives of this paper are: to measure the response of acoustic venting materials in the ultrasonic frequency range, to determine the usability of these materials in ultrasonic vents, and to extract useful information for the design of efficient ultrasonic venting materials. Transmission coefficient spectra of different acoustic venting materials is measured in the frequency range 0.2 –2.7 MHz. The origin of the ultrasonic losses and frequency distortion are analysed as well as the role of mode conversion, internal interferences, modes interference, etc. Results reveal that none of the acoustic venting materials analysed can be used in ultrasonic venting applications, but the obtained knowledge about the response of these materials in the ultrasonic frequency range permit to advance in the selection of successful candidate materials for this application.

Binary-Cooperative Ultrathin Porous Membrane for Gas Separation.

The construction of ultrathin porous membranes with stable structures is critical for achieving efficient gas separation. Inspired by the binary-cooperative structural features of bones and teeth-composed of rigid hydroxyapatite and flexible collagen, which confer excellent mechanical strength-a binary-cooperative porous membrane constructed with gel-state zeolitic imidazolate frameworks (g-ZIFs), synthesized using a metal-gel-induced strategy, is proposed. The enlarged cavity size and flexible frameworks of the g-ZIF nanoparticles significantly improve gas adsorption and diffusion, respectively. After thermal treatment, the coordination structures forming rigid segments in the g-ZIF membranes appear at the stacked g-ZIF boundaries, exhibiting a higher Young's modulus than the g-ZIF nanoparticles, denoted as the flexible segments. The g-ZIF membranes demonstrate excellent tensile and compression resistances, attributed to the effective translation of binary-cooperative effects of rigidity and flexibility into the membranes. The resulting dual-aperture structure, composed of g-ZIF nanoparticles surrounded by nanoscale apertures at the boundaries, yields a membrane with a stable CO2 permeance of 4834 GPU and CO2/CH4 selectivity of 90 within 3.0MPa.

Unveiling the impacts of salts on halotolerant bacteria during filtration: A new perspective on membrane biofouling formation in MBR treating high-saline organic wastewater

In recent decades, membrane bioreactor (MBR) has been prevalently employed to treat high-saline organic wastewater, where the halotolerant microorganisms should be intensively utilized. However, limited works were devoted to investigating the biofouling characteristics from the perspective of the relationship between halotolerant bacteria and salts. This work filled the knowledge gap by exploring the biofouling formation mechanisms affected by high salinity. The results showed that the amount of negative charge on halotolerant bacteria surface was significantly reduced by high content of NaCl, probably leading to the obvious cell agglomeration. Despite the normal proliferation, the halotolerant bacteria still produced substantial EPS triggered by high salinity. Compared with the case of control without salt addition, the enhanced biofouling development was observed under high-saline conditions, with the fouling mechanism dramatically transformed from cake filtration to intermediate blocking. It was inferred that the halotolerant bacteria initially adhered on membrane created an extra filter layer, which contributed to the subsequent NaCl retention, resulting in the simultaneous occurrences of pore blockage and cake layer formation because of NaCl deposition both on membrane pores as well as on biofilm layer. Under high-saline environment, remarkable salt crystallization occurred on the biofilm layer, with more protein secreted by the attached halotolerant bacteria. Consequently, the potential mechanisms for the enhanced biofouling formation influenced by high salinity were proposed, which should provide new insights and enlightenments on fouling control strategies for MBR operation when treating high-saline organic wastewater.

Electro-Fenton enhanced MBR for fouling alleviation based on MIL-88B-Fe derived carbon membrane with in-situ generated [rad]OH

Porous carbon membrane (PCM) derived from MIL-88B-Fe with the ability of in-situ generation of hydroxyl radical was introduced to electro-enhanced aerobic membrane bioreactor (EMBR) for membrane fouling mitigation and wastewater quality improvement. The resultant PCM obtained with the calcination temperature of 1000 °C owned significant enhancement on hydrophilic and conductive properties, which helped PCM under −1.2 V could completely remove 10 mg/L bovine serum albumin with 2.5 % membrane flux loss rate. During the 76-day operation of EMBR, the extracellular polymeric substances could be suppressed for depositing on the −1.2 V enhanced PCM due to the combined effect of electrostatic barrier and OH oxidation. The pollutant intensity of total cells, polysaccharides and proteins were all reduced on PCM with −1.2 V. After operation, 36.0 % of cake layer pores was blocked in EMBR by total cells, polysaccharides and proteins. However, it was accounted for 69.8 % of the control group. Above results explained why the EMBR owned an always lower transmembrane pressure. Meanwhile, the pollutants removal rates of COD and NH4+-N were as high as 95 % and 98 % with electro-enhanced filtration, respectively, which is attributed to the collaborated effect from electrochemical effect and significantly increased microbial species related to organic pollutants removal, such as Azohydromonas, Thermomonas.

Sub-nanometer size level regulation of biomimetic channels in porous membrane for high-capacity removal of toxic dye contaminants

Organic dyes are an important chemical with a market demand of millions of tons. However, their massive emissions, especially alkaline dye contaminants, have caused serious disruption of the ecosystem and even cancers. Inspired by bionic mass transfer, several amino acid fragments (carboxylic acid, γ-aminobutyric acid, and glutamic acid) are introduced into the 2.5 nm-pore size cavity through in-situ polymerization. The flexible amino acid chains facilitate the transport of guest molecules into the channels, accelerating their movement within the porous framework. These flexible chains are implanted into a 2.5 nm pore cavity, forming a 0.8–1.5 nano-meter-sized confinement space, bringing about the strong absorption capability for alkaline contaminants. Notably, LNU-74-glutamic acid achieves an ultra-fast absorption rate for toxic dye contaminants (4.74 g g−1h−1), as well as the highest capacity per unit area among all reported porous adsorbents, including porous carbons, metal–organic frameworks, porous polymers. After encapsulation in commercial polymer, the mixed-matrix membrane reveals (LNU-74-glutamic acid@MMM) a rejection rate greater than 98 % in various real water environments at permeation flux of ∼320 L m−2h−1, including strong acid/alkali, river water, and seawater.

Mechanism and molecular level insight of refractory dissolved organic matter in landfill leachate treated by electroflocculation coupled with ozone

Landfill leachate usually contains a substantial content of refractory dissolved organic matter (RDOM), which mainly consists of humic acid and fulvic acid. RDOM easily blocks the membrane pores resulting in membrane fouling when treated using membrane technologies, and it costs abundant chemical regents using advanced oxidation processes. To achieve the economically efficient treatment of RDOM in landfill leachate, this study established the electroflocculation coupled with ozone (EFCO) system. EFCO achieved a higher removal for organic matter than single electroflocculation and ozonation, where RDOM was the main component of organic matter in landfill leachate. The remaining RDOM was decomposed into lots of micromolecule weight and biodegradable proteins and lipids. Ozone improved the removal of dissolved organic matter (DOM) mainly by changing the functional groups on its surface and improving the mechanical strength of flocs to enhance the complexation between flocs and DOM. Cl2− and ClO produced in the EFCO system were the main active chlorine species, which enhanced the mineralization of RDOM. The study provides an efficient method for the pretreatment of RDOM in landfill leachate.

Two birds with one stone: Bimetallic ZnCo2S4 polyhedral nanoparticles decorated porous N-doped carbon nanofiber membranes for free-standing flexible anodes and microwave absorption

Cost-efficient material with an ingenious design is important in the engineering applications of flexible energy storage and electromagnetic (EM) protection. In this study, bimetallic ZnCo2S4 (ZCS) polyhedral nanoparticles homogenously embedded in the surface of porous N-doped carbon nanofiber membranes (ZCS@PCNFM) have been fabricated by electrospinning technique combined with carbonization and hydrothermal processes. As a self-assembled electrode for lithium-ion batteries (LIBs), the bimetallic ZCS nanoparticles possess rich redox reactions, good electrical conductivity, and pseudocapacitive properties, while the three-dimensional (3D) multiaperture architecture of the nanofiber film not only shortens the transfer spacing of lithium ions and electrons but also effectively tolerates the volume variation during lithiation and delithiation cycles. Benefiting from the above merits, the ZCS@PCNFM electrode exhibits good cycle performance (662.3 mA h/g at 100 mA/g after 100 cycles), superior rate capacity (401.3 mA h/g at 1 A/g) and an extremely high initial specific capacity of 1152.2 mAh/g at 100 mA/g. Meanwhile, depending on the hierarchical nanostructure and multi-component heterogeneous interface effects constructed by 3D inlaid architecture, the ZCS@PCNFM nanocomposite exhibits fascinating microwave absorption (MA) characteristics with a superhigh reflection loss (RL) of –49.7 dB at a filling content of only 20 wt% and corresponding effective absorption bandwidth (EAB, RL<–10 dB) of 5.2 GHz ranging from 12.8 to 18.0 GHz at 2.2 mm.

Effects of surfactants, ion valency and solution temperature on PFAS rejection in commercial reverse osmosis (RO) and nanofiltration (NF) processes

Per- and polyfluoroalkyl substances (PFAS) have garnered attention as a pressing environmental issue due to their enduring presence and suspected adverse health effects. This study assessed the rejection or removal efficacy of PFAS by commercial reverse osmosis (RO) and nanofiltration (NF) membranes and examined the impacts of surfactants, ion valency and solution temperature that are inadequately explored. The results reveal that the presence of cationic surfactants such as cetyltrimethylammonium bromide (CTAB) increased the rejection of two selected PFAS compounds, perfluorooctanoic acid (PFOA) and perfluorobutanoic acid (PFBA), by binding with negatively charged PFAS and preventing them from passing through membrane pores via size exclusion, whereas the presence of anionic surfactants such as sodium dodecyl sulfate (SDS) increased the PFAS rejection because the increased electrostatic repulsion prevented PFAS from approaching and adsorbing onto the membrane surface. Moreover, aqueous ions (e.g., Al3+ and PO43−) with higher ion valency enabled higher rejection of PFOA and PFBA through increased effective molecular size and increased electronegativity. Finally, only high solution temperature at 45 °C significantly reduced PFAS rejection efficiency because of the thermally expanded membrane pores and thus the increased leakage of PFAS. Overall, this research provides valuable insights into the various factors impacting PFAS rejection in commercial RO and NF processes. These findings are crucial for developing efficient PFAS removal methods and optimizing existing treatment systems, thereby contributing significantly to the ongoing efforts to combat PFAS contamination.

Characterization of drusen formation in a primary porcine tissue culture model of dry AMD

Age-related macular degeneration (AMD) affects millions of individuals worldwide and is a leading cause of blindness in the elderly. In dry AMD, lipoproteinaceous deposits called drusen accumulate between the retinal pigment epithelium (RPE) and Bruch's membrane, leading to impairment of oxygen and nutrient trafficking to the neural retina, and degeneration of the overlying photoreceptor cells. Owing to key differences in human and animal ocular anatomy and the slowly progressing nature of the disease, AMD is not easily modeled invivo. In this study, we further characterize a "drusen-in-a-dish" primary porcine RPE model system by employing vital lipid staining to monitor sub-RPE deposition over time in monolayers of cells cultured on porous transwell membranes. We demonstrate for the first time using a semi-automated image analysis pipeline that the number and size of sub-RPE deposits increases gradually but significantly over time and confirm that sub-RPE deposits grown in culture immunostain positive for multiple known components found in human drusen. As a result, we propose that drusen-in-a-dish cell culture models represent a high-throughput and cost-scalable alternative to animal models in which to study the pathobiology of drusen accumulation and may serve as useful tools for screening novel therapeutics aimed at treating dry AMD.

Asymmetric Poly(ionic liquid) Porous Membranes by Nonsolvent-Induced Phase Separation

Asymmetric Poly(ionic liquid) Porous Membranes by Nonsolvent-Induced Phase Separation

Membrane transport of rare earth metal ions N, N’-bisdioctylphosphorylmethyl-1,4-diaminobutane by the active transport mechanism

The method of membrane extraction for rare earth elements (REE) using the carrier N, N’-bisdioctylphosphorylmethyl-1,4-diaminobutane (DPDA-8) ions, leveraging an active transport mechanism, has been optimized. The distribution of DPDA-8 within the membrane pores was confirmed using scanning electron microscopy (SEM). Both light and heavy REE extractions from a simulated solution using DPDA-8 and trioctylphosphine oxide (TOPO) in 1,2-dichlorobenzene were explored. The influence of feed solution pH, carrier and anion concentration, supported liquid membrane (SLM) type and stability, and cell temperature, among other parameters, were meticulously examined. The results indicate a decrease in permeability with a decrease in feed solution pH attributed to competitive acid transport through the membrane. Additionally, the formation of H-complexes between carriers and perchloric or phosphoric acids was investigated using Fourier Transform Infrared (FTIR) spectroscopy and X-ray diffraction (XRD) techniques. Changes in the stretching bands of amino and phosphine oxide groups in DPDA-8 were monitored and characterized. XRD analysis of the crystal structures of salts DPDA-6·ClO4 and DPDA-12·H2PO4 revealed a two-dimensional layered supramolecular organization with varying anion positions relative to hydrophobic fragments. The DPDA-8 carrier demonstrated significantly higher permeability values compared to TOPO, with differences in permeability exceeding twofold for certain metals. FTIR spectroscopy identified the main coordination centers of DPDA-8 during the liquid–liquid extraction of specific REEs.