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Environmental toxins threaten human health and ecosystem integrity, necessitating advanced detection, degradation, and removal methodologies. In recent years, the scientific community has increasingly focused on MXenes, a novel class of two-dimensional (2D) transition metal carbides, nitrides, and carbonitrides, due to their exceptional potential in toxin management. This comprehensive review thoroughly examines MXenes, including synthesis methods, structural and chemical properties, and functionalization strategies. Unique to this review is the integrated discussion of MXenes in the context of environmental toxin management, encompassing detection, degradation, and removal within a single study. The enhancement of sensor technologies using MXenes for rapid and precise toxin detection is thoroughly analyzed. It focuses on MXene-mediated degradation pathways, especially photocatalytic and electrocatalytic mechanisms, considering their redox potential and light-harvesting capabilities. Additionally, the adsorption dynamics of MXene-based adsorbents are scrutinized, covering adsorption capacity, kinetics, and regeneration/recyclability. The review offers a comparative evaluation of MXenes with other 2D materials, positioning MXenes within the broader context of toxin management solutions. This article stands out for its novel and comprehensive approach, being the first to concurrently address the detection, degradation, and removal of environmental toxins using MXenes. The review concludes by underscoring the vast potential of MXenes in addressing environmental toxins. It emphasizes the urgent need for continued research to optimize their performance, scale up production, and enable practical implementation. This detailed reference aims to serve researchers and practitioners in environmental management, guiding future innovations and applications of MXenes in toxin control.

Thallium is a highly toxic metal, and trace amount of thallium(I) (Tl+) in potable water could cause a severe water crisis, which arouses the exploitation of highly-effective technology for purification of Tl+ contaminated water. This report proposes the multi-layered Prussian blue (PB)-decorated composite membranes (PBx@PDA/PEI-FP) based on the aminated filter papers for Tl+ uptake. Extensively characterization by Fourier transform infrared spectrometer-attenuated total reflectance, scanning electron microscope, thermogravimetric analysis, X-ray photoelectron spectroscopy and X-ray diffraction were performed to confirm the in situ growth of cubic PB crystals on filter paper membrane surfaces via the aminated layers, and the successful fabrication of multi-layered PB overcoats via the increasing of aminated layers. The effect of PB layers on Tl+ removal by PBx@PDA/PEI-FP from simulated drinking water was evaluated as well as the influence of different experimental conditions. A trade-off between PB decoration layer number and PB distribution sizes is existed in Tl+ uptake by PBx@PDA/PEI-FP. The double-layered PB2@PDA/PEI-FP membrane showed the maximum sorption capacity, but its Tl+ uptake performance was weakened by the acid, coexisting ions (K+ and Na+) and powerful operation pressure, during filtrating a large volume of low-concentrated Tl+-containing water. However, the negative effect of coexisting ions on the Tl+ uptake could be effectively eliminated in weak alkaline water, and the Tl+ removal was increased up to 100% without any pressure driving for PB2@PDA/PEI-FP membrane. Most importantly, PB2@PDA/PEI-FP displayed the high-efficiency and high-selectivity in purifying the Tl+-spiked Pearl River water, in which the residual Tl+ in filtrate was less than 2 µg·L−1 to meet the drinking water standard of United States Environmental Protection Agency. This work provides a feasible avenue to safeguard the drinking water in remote and underdeveloped area via the energy-free operation. [ABSTRACT FROM AUTHOR]

Transition metal dichalcogenide nanosheet (TMDN)-based adsorbents possess promising Pb2+ removal capabilities due to their distinctive Lewis acid/base soft–soft interactions with Pb2+, nevertheless, which still suffer from drawbacks including vulnerability in complex aqueous solutions. In this work, aramid nanofibers (ANFs) with excellent structural stabilities were applied as the support materials for in situ growth of MoS2 nanosheets, and the obtained delicately fibrous ANF/MoS2 can be molded into aerogels and membranes through a vacuum filtration process. On account of the Pb2+ complexation capacity of both sulfur atoms in MoS2 nanosheets and nitrogen/oxygen atoms in the ANF and superior structural stabilities in chemical solvents and high-temperature conditions, such hybrid aerogels exhibited efficient and fast Pb2+ adsorption capacities (∼187.9 mg/g at 25 °C, ∼327.4 mg/g at 85 °C within 150 s, pH = 5). Additionally, the obtained aerogel membranes achieved a synthetic effect of separation and adsorption that can remove more than 90% of Pb2+ from 100 mg/L Pb2+ aqueous solutions, and ∼75% rejection ratio was retained after 10 cycles at 25 °C. Therefore, our work provided a method to build aerogel adsorbents based on TMDNs that possessed remarkable performance to rapidly, efficiently, and stably adsorb Pb2+ even under harsh environments. [ABSTRACT FROM AUTHOR]

ObjectiveTo compare the effects and experimental conditions of membrane adsorption method， membrane adsorption-PEG method and membrane adsorption-ultrafiltration method on virus enrichment in purified water.MethodsMS2 bacteriophage was used as target virus to prepare water samples with high and low concentrations， and the standard curve of reverse transcription-fluorescence quantitative polymerase chain reaction （RT-qPCR） was established for quantitative detection. Water samples were enriched by membrane adsorption method， membrane adsorption-PEG method and membrane adsorption-ultrafiltration method. The recoveries of different filtration membranes， different ultrafiltration tubes and two nucleic acid extraction methods were compared.ResultsThe average recoveries of membrane adsorption-ultrafiltration method， membrane adsorption-PEG method and membrane adsorption method were 19.80% ± 12.19%， 12.71% ± 9.09% and 9.05% ± 4.89%. The order of influencing factors on the recoveries was： membrane adsorption-ultrafiltration method > membrane adsorption-PEG method > membrane adsorption method. High concentration > low concentration. The effect of virus enrichment of mixed cellulose ester membrane was better than nylon membrane. There was no difference in the enrichment effect of ultrafiltration tube at 100 and 50 K， and the nucleic acid extraction effect of silica gel centrifugation column method and magnetic bead method.ConclusionThe enrichment efficiency can be improved by secondary enrichment. Membrane adsorption-ultrafiltration method is simple to operate， short time consuming， low dependence on equipment， and easy to be popularized. The experimental conditions of membrane adsorption-ultrafiltration can be optimized and improved to expand the application of different water bodies and different virus enrichment.

Unravelling the mechanisms of action of disinfectants is essential to optimise dosing regimes and minimise the emergence of antimicrobial resistance. In this work, we examined the mechanisms of action of a commonly used disinfectant—benzalkonium chloride (BAC)—over a significant pathogen—L. monocytogenes—in the food industry. For that purpose, we used modelling at multiple scales, from the cell membrane to cell population inactivation. Molecular modelling revealed that the integration of the BAC into the membrane requires three phases: (1) the approaching of BAC to the cellular membrane, (2) the absorption of BAC to its surface, and (3) the integration of the compound into the lipid bilayer, where it remains at least for several nanoseconds, probably destabilising the membrane. We hypothesised that the equilibrium of adsorption, although fast, was limiting for sufficiently large BAC concentrations, and a kinetic model was derived to describe time–kill curves of a large population of cells. The model was tested and validated with time series data of free BAC decay and time–kill curves of L. monocytogenes at different inocula and BAC dose concentrations. The knowledge gained from the molecular simulation plus the proposed kinetic model offers the means to design novel disinfection processes rationally. [ABSTRACT FROM AUTHOR]

Unravelling the mechanisms of action of disinfectants is essential to optimise dosing regimes and minimise the emergence of antimicrobial resistance. In this work, we examined the mechanisms of action of a commonly used disinfectant—benzalkonium chloride (BAC)—over a significant pathogen—L. monocytogenes—in the food industry. For that purpose, we used modelling at multiple scales, from the cell membrane to cell population inactivation. Molecular modelling revealed that the integration of the BAC into the membrane requires three phases: (1) the approaching of BAC to the cellular membrane, (2) the absorption of BAC to its surface, and (3) the integration of the compound into the lipid bilayer, where it remains at least for several nanoseconds, probably destabilising the membrane. We hypothesised that the equilibrium of adsorption, although fast, was limiting for sufficiently large BAC concentrations, and a kinetic model was derived to describe time–kill curves of a large population of cells. The model was tested and validated with time series data of free BAC decay and time–kill curves of L. monocytogenes at different inocula and BAC dose concentrations. The knowledge gained from the molecular simulation plus the proposed kinetic model offers the means to design novel disinfection processes rationally.

Plant tannins have the ability to form stable complexes with metal ions, while microporous membranes have low pressure drop and high flux characteristics. Combining these two materials, a new type of tannin-immobilized membrane (M-TAN) adsorption material has been developed. The PA-BWT, PVDF-BWT, CELL -BWT, and PA-AA-BWT were prepared using different types of microporous membranes as substrates, which maintained the porous structure of the membranes and had the characteristics of high flux and fast filtration rate. The surface contact angle and pure water flux analysis showed that the introduction of tannin with multi-phenolic hydroxyl groups increased the hydrophilicity and water flux of the M-TANs. The adsorption performance shows that the adsorption capacity of four kinds of M-TANs for UO22+ is in the order of PA-BWT > PA-AA-BWT > PVDF-BWT > CELL-BWT, and PA-BWT has the largest adsorption capacity of 0.398 mmol g−1. In addition, the adsorption isothermal and kinetic data of PA-BWT were well fitted by the Langmuir equation and the Elovich model, respectively. The negative values of ΔG for UO22+ adsorption on PA-BWT indicated that adsorption is a spontaneous and favorable process. These facts indicate that PA-BWT can be used as a low-cost adsorbent for effective removal of UO22+ from aqueous solutions. [ABSTRACT FROM AUTHOR]

Although dye removal from wastewater streams has been investigated via several approaches using adsorbents, resins, or membranes, it is still hard to avoid the fact that dyes are persistently left in the adsorption materials or washing solutions used to regenerate the used adsorbents. In particular, given that cleaning agents are composed of acid/base, organic solvents, or electrolytes, dye adsorption and adsorbent regeneration processes leave behind more hard-to-manage wastewater containing dyes. In this study, we demonstrated that cold plasma (CP) treatment, which is one of the advanced oxidation processes (AOPs), can be used for zero discharge of dyes and regeneration of a washing solution in a membrane-based dye removal process. Specifically, CP treatment was found to successfully remove dyes released from a washing process to regenerate a used membrane, thereby effectively recycling a cleaning solution. As a result, the regenerated washing solution was more favorable for the adsorbed dyes’ elution, leading to the successful regeneration of a used membrane without a significant loss of dye removal efficiency. This fact was evidenced by a comparative study on the effect of CP treatment on the reusability of membranes and washing solutions and the kinetic analysis of the AOP of the desorbed dyes. We hope that this study contributes to opening a new door for environmentally friendly and sustainable dye removal.

β-Amyloid (Aβ) is a 39–43 residue peptide involved in the pathogenesis of Alzheimer's disease. Aβ deposits onto the cells and gives rise to the plaques that are characteristic of the disease. In an effort to understand the molecular mechanism of plaque formation, we have examined the interaction of Aβ42, considered to be the most pathogenic of the peptides, with lipid bilayers consisting of 1-palmitoyl-2-oleoyl phosphatidylcholine (POPC) to which small amounts of GM1 ganglioside (1–5 mol%) were incorporated. POPC bilayers exist in the fluid, or liquid-disordered state at room temperature, mimicking the fluidity of cell membranes. An Aβ42 preparation consisting essentially of peptide monomers was used. A combination of molecular dynamics (MD), isothermal calorimetry and Langmuir balance measurements was applied. Our results show that Aβ binds POPC bilayers, and that binding increases (ΔG of binding decreases) with GM1, but only up to 3 mol% of the ganglioside, larger concentrations appearing to have a lower effect. MD and Langmuir balance measurements concur in showing that the peptide adsorbs onto the bilayer surface, but does not become inserted into it at surface pressures compatible with the cell membrane conditions. Thioflavin T measurements agree with MD in revealing a very low degree of peptide oligomerization/aggregation under our conditions. This is in contrast with previous studies showing peptide aggregation and insertion when interacting with membranes in the liquid-ordered state. The present contribution underlines the importance of bilayer lipid composition and properties for Aβ plaque formation. [ABSTRACT FROM AUTHOR]

Nutrient recovery from anaerobic digestate through electrodialysis technology (ED) has been investigated and shown high promise, but the removal of 17β-estradiol (E2), which is a natural estrogen and widely found in manure digestate, is not clear. This study examined the mechanism of membrane adsorption and anodic oxidation of E2 during recovering nutrient from manure digestate, and further investigated the performance of Anode-ED in E2 removal. The results showed that the removal of E2 in conventional ED was primarily attributed to membrane adsorption, resulting in no detectable E2 in the product solution. The adsorption capacity of the anion exchange membrane for E2 was significantly higher compared to that of the cation exchange membrane. During Anode-ED operation, E2 was efficiently removed by electrochemical oxidation, in which the chlorination played a primary role. Moreover, the oxidation intermediates of E2 were further removed after 40 min. Even though the carbonate, volatile fatty acid (VFA), and humic acid in the real wastewater have a negative impact on E2 oxidation, the E2 was completely removed from digestate during nutrient recovery in the anode-ED. This study indicates that anode-ED is a promising technology for the removal of E2 during nutrient recovery from digestate. [Display omitted] • E2 can not be completely removed during nutrient recovery in conventional ED. • Membrane adsorption played a role in E2 removal in conventional ED. • E2 was efficiently removed in Anode-ED reactor by electrochemical oxidation. • Anode-ED is a promising technology to remove E2 during nutrient recovery from digestate. [ABSTRACT FROM AUTHOR]

Plant tannins have the ability to form stable complexes with metal ions, while microporous membranes have low pressure drop and high flux characteristics. Combining these two materials, a new type of tannin-immobilized membrane (M-TAN) adsorption material has been developed. The PA-BWT, PVDF-BWT, CELL -BWT, and PA-AA-BWT were prepared using different types of microporous membranes as substrates, which maintained the porous structure of the membranes and had the characteristics of high flux and fast filtration rate. The surface contact angle and pure water flux analysis showed that the introduction of tannin with multi-phenolic hydroxyl groups increased the hydrophilicity and water flux of the M-TANs. The adsorption performance shows that the adsorption capacity of four kinds of M-TANs for UO22+ is in the order of PA-BWT > PA-AA-BWT > PVDF-BWT > CELL-BWT, and PA-BWT has the largest adsorption capacity of 0.398 mmol g−1. In addition, the adsorption isothermal and kinetic data of PA-BWT were well fitted by the Langmuir equation and the Elovich model, respectively. The negative values of ΔG for UO22+ adsorption on PA-BWT indicated that adsorption is a spontaneous and favorable process. These facts indicate that PA-BWT can be used as a low-cost adsorbent for effective removal of UO22+ from aqueous solutions.

The purification process of wastewater containing heavy metal ions (HMIs) using nano-fibrous metal-organic frameworks, MOF-808, embedded polyacrylonitrile membrane has been studied. The process parameters that were evaluated included feed concentration, transmembrane pressure (TMP), and membrane thickness. The effect of coexisting cations in the solution upon the removal efficiencies of Zn2+, Cd2+, Pb2+ and Hg2+ ions was also investigated. Results from the filtration experiments indicate a substantial variation in the feed volume that the membrane can treat before the permeate lead concentration reaches the allowable limit of 10 ppb, depending on the process parameter. An increase in the membrane thickness showed a significant improvement (26%) with 440 L of the treated feed volume after doubling the membrane layer. An increase in TMP could reduce the treated feed volume by 38% while a decrease in feed concentration led to a 21% increase in the treated feed volume. In the presence of other common background cations in the solution, the removal efficiency of HMIs by adsorption onto MOF-808 dropped by 18 to 37%. This result was dependent upon the HMIs, in the presence of up to three other cations but was minimal in the presence of a single cation indicative of good selectivity. Unlabelled Image • Metal-organic frameworks particles were enmeshed into polyacrylonitrile nanofiber membranes. • The membranes were used for the removal of Pb2+ ions from aqueous solution by adsorption. • The effects of transmembrane pressure, feed conc., and membrane thickness were investigated. • The presence of background ions on adsorption Zn2+, Cd2+, Pb2+ and Hg2+ ions was studied. • The filtration system could produce >500 L of pure water per m2 of membrane. [ABSTRACT FROM AUTHOR]

• Fabrication of natural zeolite based ceramic membrane for ammonia removal. • Effect of sintering temperature on HFCM's properties and performance was studied. • Sintering temperature of 1050 °C has produced the best HFCM. • Ammonia removal using the fabricated HFCM gave nearly 90% rejection. • Synergism between adsorption and separation resulted to the high ammonia removal. The excessive presence of ammonia has led to serious potable water scarceness worldwide. This work aims to fabricate natural zeolite based hollow fibre ceramic membrane (HFCM) via phase inversion and sintering techniques for the ammonia removal in wastewater. The physical properties of the fabricated HFCM were investigated through morphologies, mechanical strength, dope suspension viscosity and pure water permeation also the performance test using synthetic wastewater. It was found that 5 cm, 15 mL/min and 1050 °C were the best fabrication conditions for the air – gap distance, bore fluid flow rate and sintering temperature, respectively. The membrane also revealed desired asymmetric structure, sufficient mechanical strength (50.92 MPa) and excellent pure water permeation flux (249.57 L/m2 h). Additionally, the ammonia removal gave an outstanding performance of 90% rejection. These findings show that natural zeolite based HFCM has a great potential to be developed as a single – step ammonia removal in wastewater. [ABSTRACT FROM AUTHOR]

Graphene stratiform membrane materials have been recently applied to heavy metal removal in aqueous systems via adsorption due to their high mechanical strength, chemical stability, and other properties. We applied reduced graphene oxide (rGO) alone as an adsorbent to remove heavy metal ions from wastewater. Self-supported rGO membrane was prepared using a green reduction method with sodium hydrosulfite. We used the Raman spectra to observe the structure of the rGO membrane. The morphology of the self-supported membrane was measured by a scanning electron microscope. The Cu2+ adsorption performance was measured in terms of pH, reaction time, metal ion concentration, and temperature. The maximum Cu2+ adsorption capacity of the rGO membrane was found to be 149.25 mg/g. The adsorption process followed a pseudo-second-order kinetic model, and adsorption isotherms were simulated by the Freundlich model.

Graphical abstract Highlights • A simple mathematical model was presented for membrane adsorption by nanofibrous membrane. • A model based on the combined Carmen-Kozeny equation and Darcy’s law. • A model based on mass balance reproduction of the breakthrough curve of heavy metal ions. • Model parameters were correlated to membrane properties and operating conditions. Abstract The environmental consequences of lead ion accumulation have been linked to detrimental health impacts in humans. Hence, removal of heavy metal (lead, Pb) ions by membrane adsorption/filtration was studied in this work using nanofibrous membranes in which the adsorbent metal-organic framework, MOF-808, was embedded. S-shaped breakthrough curves were obtained experimentally when the heavy metal concentration in the permeate was plotted vs the filtration period. Simple model equations that enable the reproduction of the S-shaped breakthrough curve were derived. It was found that the model equations could simulate the experimental data reasonably well. Attempts were further made to correlate the parameters involved in the model equations to the properties of mixed matrix nanofibrous membranes, including the pore size and pore size distribution, membrane thickness, fiber diameter, the adsorption rate constant, the Langmuir adsorption constant and the maximum adsorption capacity. The model equation parameters were also correlated to the operating conditions including the heavy metal concentration in the feed and the transmembrane pressure difference. It is believed that the model equations, despite this simplicity, can provide deeper insight into the membrane adsorption/filtration phenomena. These equations also contribute to the process design for successful removal of heavy metal ions from the environment to improve health factors for humans. [ABSTRACT FROM AUTHOR]

The developmental ion imprinted nanocomposite membranes (IINcMs) had been achieved highly effective adsorption lithium from compound. Here, dopamine was introduced as surface-adherent material and hydrophilic Ag nanoparticles were deposited on the membrane surface to that integrate nanocomposite structure. More important, we investigated the selective adsorption capacity for lithium from high magnesium and low lithium. In this work, IINcMs presented relatively higher membrane flux value of 10.8 mL cm −2  min −1 and it possessed that the contact angle value was 67.746°, which indicated the fabricated membrane with high hydrophilicity that due to the presence of polydopamine (PDA) thin layer Ag nanoparticles on the IINcMs surface could enhance the interaction between membrane and water. Meanwhile, largely enhanced permselectivity (the permeation factor β values were 8.94) and structural stability (still maintained 92.1% of the maximum adsorption capacity after 10 cycling operations) had been successfully achieved, which should be attributing to the creation of uniform growth of PDA thin layer and Ag nanoparticles onto the porous membrane structure surface. Specifically, the as-prepared IINcMs also exhibited rapidly adsorption dynamics for lithium. Overall results suggest that dopamine and Ag nanoparticles can be considered as an effective additive for ion imprinted membranes in the adsorption of lithium. It is worth mentioning that IINcMs applied to selectively recognize and adsorb lithium, which was environmentally friendly without secondary pollution. [ABSTRACT FROM AUTHOR]

In this study, an innovative nano-material was prepared, which was ultilized to removal of heavy metal ions from wastewater. Polyacrylonitrile/cellulose acetate (PAN/CA) composite nanofibrous membranes were generated by the electronspinning technique first, and then amidoxime ployarcylonitrile/regenerate cellulose (AOPAN/RC) composite nanofibrous membranes were prepared by combining hydrolysis and amidoximation modification. The modification of composite nanofibers (AOPAN/RC) were consequently used in heavy metal ions adsorption. The characterizations of various different nanofibers were analyzed using scanning electron microscopy, Fourier transform infrared spectroscopy, surface area and pore size distribution analyzer and energy dispersive X-ray spectroscopy. Meantime, the adsorption equilibrium studies were studied. In addition, the saturation adsorption amount of nanofibrous membranes (at 25 °C) for Fe(III), Cu(II) and Cd(II) of 7.47, 4.26 and 1.13 mmolg −1 , respectively. The effects of pH value of solution, adsorption time and ions concentration on adsorption capacity were also investigated. Furthermore, the composite nanofibrous membranes after five times consecutive adsorption and desorption tests, the desorption rate of the Fe(III), Cu(II) and Cd(II) mental ions maintained more than 80% of their first desorption rate, AOPAN/RC composite nanofibrous reflected excellent resuability. [ABSTRACT FROM AUTHOR]

Micellar-enhanced ultrafiltration (MEUF) processes of resorcinol, phenol, and 1-Naphthol with rhamnolipid as an anionic biosurfactant were investigated using polysulfone membrane. The effects of retentate/permeate concentration of phenolic pollutants ( C / C ), distribution coefficient of phenolic pollutions ( D), concentration ratios of phenolic pollutions ( α ) and rhamnolipids ( α ) and adsorption capacity of the membrane ( N ) were studied by operating pressure, pH condition, feed surfactant, and phenolic pollution concentrations. Results showed that C (with pH) increased and ranked in the following order: resorcinol > phenol > 1-Naphthol, which is same with C (with pressure), C (with surfactant), C / C (with pollution), α, and D, while C (with pH), C (with pressure), and C (with surfactant) ranked in the reverse order. The operating pressure increased the solubility of phenolic from 0 to 0.1 MPa and then decreased slowly above 0.1 MPa. The concentration ratio of rhamnolipid was nearly at 2.0 and that of phenolic pollution was slightly above 1.0. D of phenolic pollutants reached the maximum at phenolic pollution concentration of 0.1 mM and the feed rhamnolipid concentration at 1 CMC. Moreover, zeta potential in feed stream and retentate stream and membrane adsorption of phenolic pollutions were firstly investigated in this article; the magnitudes of zeta potential with the feed stream of three phenolic pollutions were nearly the same and slightly lower than those with the retentate stream. The adsorption capacity of the membrane ( N ) was calculated and compared to the former research, which showed that rhamnolipid significantly decreases the membrane adsorption of phenolic pollutions at a relatively lower concentration. It was implied that rhamnolipid can be substituted for chemical surfactants. [ABSTRACT FROM AUTHOR]

A polytetrafluoroethylene (PTFE) double layer microfiltration membrane has been modified with zeolite imidazolate metal organic frameworks-8 (ZIF-8) and tested for micropollutants removal from water. The physical properties of the modified membrane and its removal characteristics are tested using progesterone as a model pollutant. Compared to the unmodified membrane, incorporation of ZIF-8 onto the polymer matrix resulted in close to 40% increase in the membrane adsorption capacity and almost doubling its water permeability which could result in significant reduction in processing specific energy consumption. The membrane maintained near 95% of its original removal efficiency after three regeneration cycles using polyethylene glycol-400. Modeling of the adsorption results agreed satisfactorily with the experimental measurements. The synergy provided by using ZIF-8 particles and the significant regeneration volume reduction ratio demonstrates the effectiveness of the approach for increasing the overall micropollutants removal capacity and allows for its further consideration for development of viable continuous membrane adsorption techniques for decontamination of water resources. [ABSTRACT FROM AUTHOR]

Polyvinylidene fluoride (PVDF) and hydrophobic silica sol (Si-R) hybrid hollow fiber membranes were fabricated by dry-jet wet spinning. The morphology and surface roughness of the PVDF/Si-R hybrid membranes were examined by scanning electron microscope (SEM) and atomic force microscopy (AFM), respectively. FTIR and contact angle analysis were used to characterize hydrophobic Si-R particles in the hybrid membrane. The membrane adsorption efficiency for dissolved organics including BETX (benzene, toluene, ethyl benzene and xylene) and two fatty acids: hexanoic acid and octanoic acid, as well as the membrane regeneration ability, were investigated by membrane adsorption experiments under different pressures, feed rates and temperatures. The results revealed that the hybrid hollow fiber membranes showed a microcellular structure rather than the typical asymmetrical structure of neat PVDF hollow fiber membranes. As the membrane collecting velocity increased, the hybrid hollow fiber membranes possessed enhanced surface roughness on both inner and outer surface. The adsorption efficiency of the PVDF/Si-R hybrid hollow fiber membrane was three times higher than that of the neat PVDF membrane. The adsorption efficiency of hybrid hollow fiber membranes increased with the increase of testing pressure; however, it decreased with the increase in feed rate, and was not influenced by temperature in the range of 0–80 °C. With membrane collecting velocity of 424 cm/min, the PVDF/Si-R hybrid membrane exhibited adsorption efficiency of 94.5% and 96.7% for benzene and octanoic acid, with membrane adsorption capacities of 208.1 mg/g and 173.9 mg/g. respectively. The hybrid membrane also showed high regeneration ability with 500 ppm benzene as feed solution. The PVDF/Si-R hollow fiber membrane offers an attractive possibility for the removal of dissolved organics in oilfield produced water. [ABSTRACT FROM AUTHOR]

We report on the rational design and implementation of flowthrough (FT) platforms for purification of virus vectors (VVs) and virus-like particles (VLPs), combining anion-exchange polyallylamine membranes (Sartobind STIC) and core–shell octylamine resins (CaptoCore 700). In one configuration, the VV bulk is concentrated and conditioned with appropriate buffer in a ultra/diafiltration (UF/DF) unit prior to injection into the STIC chromatography membrane. The FT pool and an intermediate cut of the elution pool of the STIC membrane are admixed and directed to a second UF/DF. Finally, the retentate is injected into a CC700 packed bed adsorber where the purified VVs are collected in the FT pool, whereas the residual amount of DNA and host cell protein (HCP) are discarded in the eluate. The experimental recovery achieved with this downstream processing (DSP) platform is close to 100%, the DNA clearance is roughly a 4-log reduction, and the HCP level is reduced by 5 logs. The platform developed for VLP purification is simpler than the previous one, as the STIC membrane adsorber and CC700 bed are connected in series with no UF/DF unit in between. Experimentally, the FT scheme for VLP purification gave a recovery yield of 45% in the chromatography train; the experimental log reduction of DNA and HCP were 2.0 and 3.5, respectively. These results are in line with other purification strategies in the specific field of enveloped VLPs. Both DSP platforms were successfully developed from an initial design space of the binding of the major contaminant (DNA) to the two ligands, determined by surface plasmon resonance, which was subsequently scaled up and confirmed experimentally. [ABSTRACT FROM AUTHOR]

Excessive discharge of saline antibiotics wastewater into aquatic ecosystem is one crucial environmental issue facing the world today. Herein, an eco-friendly nanofiltration (NF) membrane was fabricated based on coordination complexes of tannic acid and ferric ions (TA-Fe) to selectively separate antibiotic and monovalent salt. Optimal membrane with Fe/TA molar ratio of 3/1 and coordination time of 60 s exhibited Zeta potential of −26.0 mV (pH = 7), water contact angle of 45.5o and pore radius of 0.36 nm. Consequently, TA-Fe@M3-T60 membrane showed high ciprofloxacin/NaCl rejection ratio of ~5.9 and considerable water permeability of 20.6 ± 1.2 LMH. Besides, relatively high rejection rates were obtained for ofloxacin (94.1 ± 2.2 %) and ciprofloxacin (91.9 ± 2.5 %), while rejection rate for trimethoprim was much lower (68.2 ± 4.1 %). Effects of static/dynamic membrane adsorption of antibiotics on subsequent removal performance were investigated for the first time. Rejection rate improvements of 7.4–15.2 % were observed on pristine membrane compared with pre-adsorbed membrane in short-term NF process. Electrostatic shielding experiment and rejection rate prediction further distinguished the contributions of steric hindrance, electrostatic interaction and membrane adsorption on antibiotics removal, especially antibiotics in zwitterionic form at pH = 7. The findings of this work imply that this newly developed NF membrane has great potential for efficient treatment of antibiotics-contaminated wastewater. • TA-Fe NF membrane showed high antibiotic/NaCl selectivity and desirable water flux. • Different charged antibiotics removal by TA-Fe NF membrane was explored in detail. • Membrane adsorption effectively promoted the antibiotic removal before equilibrium. • Electrostatic shielding and rejection prediction distinguished removal mechanism. [ABSTRACT FROM AUTHOR]

Hypothesis Alginate capsules have several applications. Their functionality depends considerably on their permeability, chemical and mechanical stability. Consequently, the creation of composite system by addition of further components is expected to control mechanical and release properties of alginate capsules. Experiments Alginate and alginate–sodium caseinate composite liquid-core capsules were prepared by a simple extrusion. The influence of the preparation pH and sodium caseinate concentration on capsules physico-chemical properties was investigated. Findings Results showed that sodium caseinate influenced significantly capsules properties. As regards to the membrane mechanical stability, composite capsules prepared at pH below the isoelectric point of sodium caseinate exhibited the highest surface Young’s modulus, increasing with protein content, explained by potential electrostatic interactions between sodium caseinate amino-groups and alginate carboxylic group. The kinetic of cochineal red A release changed significantly for composite capsules and showed a pH-responsive release. Sodium caseinate-dye mixture studied by absorbance and fluorescence spectroscopy confirmed complex formation at pH 2 by electrostatic interactions between sodium caseinate tryptophan residues and cochineal red sulfonate-groups. Consequently, the release mechanism was explained by membrane adsorption process. This global approach is useful to control release mechanism from macro and micro-capsules by incorporating guest molecules which can interact with the entrapped molecule under specific conditions. [ABSTRACT FROM AUTHOR]

• Interactions of anions with three different FAB-PK-130, BM-1, BM-2 membranes. • Selective AA/MA/CA recovery from ternary mixture using electrodialysis. • BM-2 microstructure resulted higher selectivity for AA− compared to other anions. • Order of ion selectivity remained at pH ∼ 7.5 is as follows: AA1− > MA2− > CA3−. • Current efficiency of 63.7% was noted with BM-2 for AA− ions at 6.0 mA·cm−2. Selective transport of carboxylic acids (acetic, AA; malic, MA; and citric, CA) from their equimolar (0.1 mol·L-1) ternary mixture was investigated through electrodialysis (ED) using three different anion exchange membranes [(i) Fumatech, FAB-PK-130, and two indigenous membranes made by solution blend of polyvinylidene fluoride (PVDF): copolymer of polymethyl methacrylate- co -polychloromethyl styrene (PMMA- co -PCMSt) at (ii) 50:50 wt% (BM-1), and (iii) 30:70 wt% (BM-2) followed by aminating them using tetramethyl 1,6 diamino hexane]. Recovery ratio (RR) for AA/MA and AA/CA mixtures were 1.97 and 2.71 respectively, indicating higher selectivity for AA through BM-2 and the same was explained based on highest ion exchange capacity (2.10 meq·g−1) and ion conductivity (2.3 mS·cm−1) data. Selective transport of AA was further endorsed by ED performance separately done with AA, MA and CA (0.1 mol·L-1 each) and equimolar binary (AA/MA) mixture at pH 7.5. Increasing trend in AA recovery: FAB-PK-130 < BM-1 < BM-2 at pH 7.5 was further supported by physical properties of the electrolyte (transport number from binary/ternary mixture) and membrane (water uptake, fractional adsorption, and ion conductivity) separately with each membrane. Highest current efficiency of 63.7% (energy consumption 5.13 kWh·kg−1) could be achieved with AA during ED analysis of ternary mixture through BM-2. [ABSTRACT FROM AUTHOR]

Highlights: [•] An in investigation in to the use of membrane chromatography for the purification of a γ-retrovirus was undertaken. [•] The first report of a capacity for γ-retrovirus binding to a membrane chromatography device is presented. [•] A process that produces a large increase in concentration and purity of the studied γ-retrovirus was identified. [•] Proteomic techniques were used to identify the protein impurities removed and co-purified with the virus containing eluate. [ABSTRACT FROM AUTHOR]

Abstract: Extracellular laccase from the fermentation broth of Pleurotus sapidus was purified using membrane chromatography. Five laccase iso-enzymes produced in submerged cultures were purified; the enzymes had isoelectric points (pI) ranging from 3.3 to 4.7 and a calculated molecular weight of 57.4kDa. The fermentation broth had a low product titre of 80μg/l. Hydrophobic interaction (HIC) and ion exchange (IEX) membranes chromatography modules were used in an ÄKTApurifier 100 liquid chromatography system for the dynamic experiments. The pre-treatment of the fermentation broth was not required. The enzyme activity was retained, and enrichment up to 15-fold was observed via activity assays and SDS-Page analysis. [Copyright &y& Elsevier]

Abstract: Polyethylene glycol (PEG) and amino-modified multi-walled carbon nanotubes (MWCNT-NH2) were utilized to modify chitosan/polyvinyl alcohol (CS/PVA) thin adsorptive membranes for copper ion adsorption. SEM, AFM, water affinity and mechanical analysis were performed for membrane characterization. Batch adsorption experiments were conducted to determine the effects of additive, pH, metal concentration and temperature on adsorption. Macroporous membranes were prepared by introducing PEG into the casting dopes; however, the upper limit for PEG loading was 5wt%. Adsorption capacity of CS/PVA membrane was increased from 11 to 30mg/g by addition of 5wt% PEG to the blend. Addition of MWCNT-NH2, especially at optimal concentration of 1wt%, improved membranes adsorption/transport behavior by creation of nanochannels and supplementary interstices in the compact CS/PVA matrix. Copper ion adsorption on CS/PVA membrane was elevated from 11 to 19mg/g by introducing 1wt% MWCNT-NH2. Thermodynamic parameters (ΔH °, ΔS ° and ΔG °) revealed endothermic nature, favorability and spontaneity of the adsorption. Moreover, kinetic studies showed that MWCNT-NH2 plays primary role in adsorption rate enhancement. Adsorptive membranes containing combined MWCNT-NH2 and PEG (called ‘CPMP’), demonstrated superior sorption capacity (∼35mg/g) and reusability among tested membranes. Finally, thin adsorptive membranes were tested in dynamic mode using a dead-end filtration setup. CPMP showed superior performance as expected. Based on the results, introducing combined MWCNT-NH2–NH2 and PEG can greatly elevate CS/PVA membranes capability for adsorptive removal of copper ions from water. [Copyright &y& Elsevier]

Abstract: Pb2+ and NO3 − are major water pollutants with severe environmental effects. Several methods were used for treating them, but most of the intended solutions failed to treat these ions simultaneously. Electrodialysis (ED) may be able to treat them, particularly after the recent progress in membrane manufacture that has led to significant improvements in the performance. In this paper, we investigated the effect of pH on ED separation of Pb2+ and NO3 − in terms of concentration ratio (CR), concentration polarization (ilim), current efficiency (η), and energy consumption (EC). The results showed that, pH between 3 and 5 was the most effective for removal of these ions. Additionally, the distribution of ions among the charged sites on the membrane surfaces was governed by pH. At low electric potentials (<10V), ion exchange/adsorption was the prevalent phenomenon occurring on the membrane surfaces, while at voltages over 25V the membranes were regenerated. Consequently, cation and anion exchange membranes could be used for water treatment at low voltages, then regenerated at higher voltages. [Copyright &y& Elsevier]

Abstract: The present study focuses the efficiency of an anion exchange polymer for the adsorption of different heavy metal ions from water samples. Solutions with different concentrations of the heavy metals were prepared and the efficiency of the ionomer in separation of the metals was evaluated by adsorption technique. Quaternized poly styrene ethylene butylene poly styrene (QAPSEBS) was used as the ionomer and it was prepared by two step method, viz. chloromethylation and amination. The membrane was prepared by solution casting method using an appropriate solvent. There are various factors affecting the metal ion adsorption on the polymer membrane such as metal ion concentration, pH, treatment time and temperature were studied. From the results obtained, it was found that the percentage adsorption increased with (a) increase in the metal ion concentration, (b) increase in the treatment time up to 2h after which it levels off, (c) decrease in temperature from 75°C to 35°C. In addition to that, the effect of extent of amination of the polymer membrane was also examined. The polymer membrane was characterized using FT-IR, 1H-NMR, DSC, TGA, XRD and SEM. The results revealed that the polymer membrane showed high efficiency in adsorption for Cr(VI) ion rather than removal of Cu(II) and Ni(II) ions. [Copyright &y& Elsevier]

Abstract: Disinfection byproducts (DBPs), trihalomethanes and haloacetic acids present in water are well known carcinogens and their removal is an important priority. Highly porous nanofibrous membrane filters produced by electro-spinning were carbonized and used for the removal of DBPs from water. In the present investigation, chloroform and monochloroacetic acid (MCAA) was used as model DBPs compounds. The DBPs concentration in the range of 1–100mg/L was used in well controlled adsorption experiments using the prepared membranes. For chloroform an adsorption capacity of 554mg/g of carbonized nanofibrous membranes (CNMs) was determined based on the filtration of feed solution (100mg/L). The adsorption capacity of MCAA was between 287 and 504mg/g for a feed concentration of 4–18mg/L based on the static adsorption study. The used membranes were regenerated by chemical/physical treatment and removal efficiencies of the regenerated membranes were determined. The DBPs removal from water was also investigated using multiwalled carbon nanotubes (MWCNTs) incorporated in the CNMs and results were compared. Although the initial removal of MCAA was increased with increasing concentration of the MWCNTs, afterwards, the subsequent removals showed no effect of addition of MWCNTs. The possible mechanism was also discussed to better understand the adsorption phenomenon. These results suggest that the CNMs could be used as DBPs removal filter for drinking water purpose. [ABSTRACT FROM AUTHOR]

Abstract: The impact of solute–solute interactions on retention and membrane adsorption of the micropollutant estrone was determined in the presence of surfactant sodium dodecyl sulphate (SDS), natural organic matter (NOM) and cellulose. A five cycle stirred cell protocol was used to study progressing saturation of a loose nanofiltration membrane with estrone. Adsorption was absent at high pH when the estrone molecule was dissociated, while at low and neutral pH the membrane was saturated after three filtration cycles and breakthrough was obvious. Increased estrone retention in the presence of cellulose was observed due to estrone–cellulose partitioning. SDS and NOM reduced estrone retention at low and neutral pH while no significant effect was visible at alkaline pH when solute–solute interactions were minimal. The adsorption and deposition of estrone onto the membrane was up to 50% of the total estrone in solution. Using experimental partition coefficients, the mass of estrone sorbed to organic matter as a function of pH was estimated. Results were similar to the total mass of estrone adsorbed to the membrane despite the partition coefficients being quantified at equilibrium (24h) while the experiment was (naturally) not. This study provides first quantifiable evidence of the impact of micropollutant–organic matter interactions in membrane filtration. [Copyright &y& Elsevier]

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Cementitious membrane (CM) is a promising microfiltration membrane with low cost for raw materials and low energy consumption of non-sintering fabrication process. A novel carbon-cementitious microfiltration membrane (CCM) was fabricated with powdered activated carbon (PAC) as an additive based on CM, to solve the low mechanical strength of CM during multiple practical uses. While maintaining adequate pure water flux and porosity, the mechanical strength of the membrane was greatly improved to ensure the stability of the membrane in the filtration process. The bending strength of the CCM was 2–3 times higher than that of CM. 10 wt% CCM has the smallest critical pore size and optimal permeability, which was chosen to be the optimal PAC doping ratio. The X-ray diffraction and FT-IR results indicated that the addition of PAC did not change the mineral composition of cement hydration products, and the appropriate amount of PAC acted as a nucleation site and accelerated hydration. The effect of size effect on bending strength was more obvious with the decrease of membrane thickness. In the membrane adsorption experiments of benzophenone-4, nitrobenzene and p -chloronitrobenzene, the CCM exhibited prominent adsorption properties than CM. These results broaden the application scope of microfiltration membranes in water treatment process. [Display omitted] • Doping PAC to improve mechanical strength of cementitious microfiltration membrane; •10 wt% CCM has the smallest critical pore size and optimal permeability; •The smaller the membrane thickness, the more enormous effect of bending strength by size effect; •CCMs can adsorb small molecule organic matter, broadening the application scope of MF. [ABSTRACT FROM AUTHOR]

Abstract: An adsorption-kinetic model has been proposed to explain β-galactosidase stability in a recirculation hollow-fibre bioreactor at different temperature. The kinetic constants of the model and its dependence on temperature have been evaluated. In addition, a study has been made of the influence of lactose and enzyme concentration on lactose hydrolysis with hollow-fibre modules made of Cuprophan® and Polysulfone®. The membrane surface areas assayed were between 1 and 1.95m2. The experimental results have been satisfactorily explained with the model proposed in a previous work. This model included the competitive inhibition of the enzyme by galactose and the enzymatic adsorption onto the membrane. The adsorption constants have been calculated, verifying the applicability of the model in the modules used. Within the experimental range analysed, the hollow-fibre module made of Polysulfone® provided the least adsorption of the enzyme and therefore was the most suitable for this enzyme and reaction. [Copyright &y& Elsevier]

Abstract: Protein-adsorbed dialysis membranes are evaluated with time-of-flight secondary ion mass spectrometry (TOF-SIMS) chemical imaging technique. Protein adsorption causing permeability change is one of big issues in the development of dialysis membranes. Bovine serum albumin adsorption onto three kinds of dialysis membranes has been evaluated with TOF-SIMS. In the present study three kinds of proteins, bovine serum albumin, α-chymotripsinogen A, and cytochrome C adsorbed onto hollow-fiber dialysis membranes, were measured by means of TOF-SIMS and then TOF-SIMS spectra were analyzed using mutual information. Then specific peaks of fragment ions related to α-chymotripsinogen A and bovine serum albumin were found, respectively. In this condition, however, specific peaks to cytochrome C were not able to find compared with other samples. Finally, chemical images of α-chymotripsinogen A and bovine serum albumin, respectively, adsorbed onto the membranes with co-existing proteins were obtained. The results of TOF-SIMS images of the proteins on the membranes show different tendency of adsorption depending on co-existing proteins. Further study is needed to study more detailed protein adsorption onto the membranes with co-existing proteins. [Copyright &y& Elsevier]

Butane isomer adsorption isotherms and diffusivities in the transport pathways through Al-ZSM-11 (MEL), Al-ZSM-5 (MFI), and B-ZSM-5 zeolite membranes were measured by a transient permeation technique. The permeate responses to feed step changes were measured between 383 and 473 K, and the diffusion was modeled as Maxwell-Stefan surface diffusion with dual-site Langmuir adsorption. The effects of adsorption and diffusion on the n-C4/i-C4 ideal selectivities were quantified, and the selectivity differences between the membranes were explained based on the adsorption properties and the diffusivities. The resistance of the porous tubular supports affected the coverage in the zeolite at the permeate boundary, and the ratio of the n-C4/i-C4 diffusion driving forces consequently increased with increasing temperature. The n-C4 diffusivities were almost the same in the three membranes, but the i-C4 diffusivities in the MEL membrane were an order of magnitude higher than those in the MFI membranes. The bulkier i-C4 molecules are apparently significantly less constrained in the straight, circular pores and slightly larger intersections of MEL zeolite, although the structural differences do not affect the mobility of n-C4. Higher i-C4 coverages in the AI-ZSM-11 and B-ZSM-5 membranes compared to the Al-ZSM-5 membrane were attributed to a smaller change in entropy upon adsorption in the channels of Al-ZSM-11 and to a higher heat of adsorption in the intersections of the more substituted B-ZSM-5. Initial transient flux overshoots and undershoots after i-C4 feed concentration changes were apparently caused by a small amount of pressure-driven flow (< 10% of the total i-C4 flux and < 0.1% of the total n-C4 flux) through parallel pathways. The effective membrane thicknesses were also estimated from the transient measurements. [ABSTRACT FROM AUTHOR]