Membrane Adsorption Research Articles

Scalable and Highly Porous Membrane Adsorbents for Direct Air Capture of CO2.

Direct air capture (DAC) of CO2 is a carbon-negative technology to mitigate carbon emissions, and it requires low-cost sorbents with high CO2 sorption capacity that can be easily manufactured on a large scale. In this work, we develop highly porous membrane adsorbents comprising branched polyethylenimine (PEI) impregnated in low-cost, porous Solupor supports. The effect of the PEI molecular mass and loading on the physical properties of the adsorbents is evaluated, including porosity, degradation temperature, glass transition temperature, and CO2 permeance. CO2 capture from simulated air containing 400 ppm of CO2 in these sorbents is thoroughly investigated as a function of temperature and relative humidity (RH). Polymer dynamics was examined using differential scanning calorimetry (DSC) and broadband dielectric spectroscopy (BDS), showing that CO2 sorption is limited by its diffusion in these PEI-based sorbents. A membrane adsorbent containing 48 mass% PEI (800 Da) with a porosity of 72% exhibits a CO2 sorption capacity of 1.2 mmol/g at 25 °C and RH of 30%, comparable to the state-of-the-art adsorbents. Multicycles of sorption and desorption were performed to determine their regenerability, stability, and potential for practical applications.

Hydrophilic membranes for effective removal of PFAS from water: Anti-fouling, durability, and reusability

Per- and polyfluoroalkyl substances (PFAS) are emerging contaminants in natural water. The polyacrylonitrile ultrafiltration membrane with an average pore size of 10.9 nm, grafted with tertiary amino groups, and subsequently quaternized, was developed to effectively adsorb PFAS in the presence of co-existing competitors. It achieved over 98 % removal of perfluorooctane sulfonic acid (PFOS) at neutral pH. Over 90 % removal efficiency was recovered within four cycles through eluent regeneration. The removal mechanism was determined, through advanced characterization and theoretical analysis, as a synergistic process of electrostatic, hydrophobic, and dipole-dipole interactions. To address potential competition in adsorption caused by natural organic matter (NOM), membrane pores were regulated to achieve selective interception of humic acid (HA, a representative NOM). Effective PFOS removal (98.4 %) maintained in the presence of abundant competitors. Furthermore, the mild regeneration method led to a flux recovery rate of 99.0 %, underscoring its resistance to contamination. The effects of versatile NOM and surfactants were also evaluated, that insignificant reduction in removal efficiency was observed. After 144th regeneration cycles (equivalent), <15 % changed in grafting moieties and <13.5 % decreased in HA removal were observed, suggesting the durability on chemical composition and interception ability. Overall, the adsorptive membranes, with reusability, anti-fouling, and durability, showed great potential for remediation of PFAS from natural water.

Efficient removal of Cr(VI) from wastewater by composite adsorptive membrane modified with polyethyleneimine (PEI)

The development of an efficient and economical method to remove the toxic Cr(VI) from water is a global challenge. This study developed a new composite adsorptive membrane by combining polyacrylonitrile (PAN) as a substrate with crosslinked polyethyleneimine (PEI) to efficiently remove Cr(VI) from wastewater. After optimizing the preparation conditions of the material, the Cr(VI) removal by PEI/GMA@PAN was investigated using batch adsorption and longer-term filtration experiments. The composite adsorptive membrane exhibited a high adsorption capacity, reaching a maximum of 89.16 mg/g, along with fast adsorption kinetics that achieved equilibrium within 100 min for Cr(VI) removal. Even in the presence of coexisting ions, PEI/GMA@PAN membrane maintained a high efficiency in removing Cr(VI). The removal mechanism mainly relied on electrostatic interactions and the reduction of Cr(VI) to Cr(III). Notably, long-term filtration experiments substantiated the membrane's effectiveness in removing Cr(VI) from synthetic wastewater, with an impressive treatment volume of 342 L/m2. The optimized PEI/GMA@PAN membrane also demonstrated low PEI leaching across a wide pH range and the potential for re-utilization through four-round cycles, underscoring its promising applicability in wastewater treatment. Therefore, the newly synthesized composite membranes show potential for the removal of Cr(VI) from wastewater.

Optimal cross-linking of MXene-based membranes for high rejection and low adsorption with long-term stability for water treatment

The unique layered structure and abundant 2D nanochannels of MXene membranes have demonstrated outstanding permeability, indicating their great potential in the field of water treatment. However, their unstable interlayer spacing and irregular layer structure have limited their ability to separate small molecular pollutants effectively. In this study, we successfully prepared composite MXene membranes with high rejection and low adsorption properties by exploiting the differences in the surface functional groups and chain lengths of dopamine (DA) and polyethylene glycol (PEG) through an optimal cross-linking approach. These composite membranes exhibited excellent stability in terms of interlayer spacing and mitigated the adverse effects of stacking defects. Compared to MXene membranes, the composite membranes achieved a 1.76-fold increase in dye rejection efficiency, reaching 98.7% at most, with an adsorption ratio of only 1.8%. Moreover, outstanding performances were also exhibited in pressure and concentration load tests. Furthermore, in the context of forward osmosis applications, the composite membranes demonstrated excellent Na+ rejection of 99.9%. More importantly, these membranes showed no performance deterioration throughout 50 filtration cycles, with only a slight increase in permeance of 19.3% over a 38-day testing period. Thus, this work presents a novel solution for fabricating MXene composite membranes with low swelling, minimal defects, and high stability, enhancing its potential in the field of water and wastewater treatment.

Removal of organic matter from tofu wastewater using a combination of adsorption, Fenton oxidation, and ultrafiltration membranes

The production of tofu results in wastewater from the soaking, washing, and pressing processes. Owing to its unique composition and quality, tofu wastewater treatment involves a complex set of challenges. Wastewater from tofu production has a significantly high organic content because it contains many soybean residues and other products. This study aimed to determine the removal efficiency of tofu wastewater contaminants for a combination of adsorption, Fenton oxidation, and ultrafiltration membrane processes. The best strategy for turbidity removal, with a removal value of 99.78%, was an integrated system combining adsorption and ultrafiltration membranes. The most optimal method for reducing organic matter contained in tofu wastewater is Fenton oxidation with TSS, COD and turbidity removal values of 81.11%, 95.13% and 62.42%. Moreover, microphotography analysis using scanning electron microscopy showed an irregularly shaped surface layer with the particles spaced far apart when granular active carbon adsorption was integrated with an ultrafiltration membrane. The results were inversely proportional when Fenton oxidation was integrated with ultrafiltration membranes. After granular active carbon adsorption, the spacing between the granules or crystals increased, whereas the granular dimensions decreased.

Methylene Blue Removal on Biodegradable Adsorptive Membranes Fabricated From Sugarcane Bagasse Pulp: Characterization and Performance Study

AbstractDye‐containing waste should be carefully treated using environmentally friendly technology to prevent environmental harm and preserve water resources. Adsorptive membranes are a promising new approach for decreasing, recovering, and reusing waste while also removing contaminants like dyes. In this work, two different techniques are employed to create membranes using sugarcane bagasse pulp and carbon from charcoal. In the first technique, the surface of sugarcane bagasse is coated with charcoal paste as shown in Figure 1, while in the second, the carbon is combined with sugarcane bagasse pulp particles before being formed into sheets. It is discovered that the manufactured membranes has micron‐sized pores. It is discovered that the mixed‐fabricated membrane has a 99.4% better efficiency than the coated one. The membranes' surfaces are characterized using FTIR and SEM analysis.

Chemical engineering and the circular water economy: Simulations for sustainable water management in environmental systems

In the face of escalating water scarcity and environmental degradation, the imperative for sustainable water management has never been more urgent. Chemical engineering emerges as a pivotal discipline in the pursuit of solutions to these pressing challenges. This review explores the role of chemical engineering in advancing the circular water economy paradigm through simulations aimed at fostering sustainable water management within environmental systems. The circular water economy concept advocates for the efficient utilization, recycling, and reclamation of water resources to minimize waste and maximize resource efficiency. Chemical engineering techniques play a fundamental role in realizing this vision through the design and optimization of water treatment processes, resource recovery systems, and advanced simulation methodologies. This review delves into the application of computational simulations within the realm of chemical engineering to model and analyze various aspects of the water cycle. Such simulations enable the assessment of complex environmental systems, aiding in the identification of optimal strategies for water resource allocation, pollution control, and ecosystem preservation. Key areas of focus include the simulation of wastewater treatment processes, such as biological, physical, and chemical treatment methods, to enhance pollutant removal efficiency and promote water reuse. Furthermore, advanced modeling techniques facilitate the evaluation of innovative technologies like membrane filtration, adsorption, and electrochemical processes for the purification and desalination of water resources. Moreover, chemical engineering simulations enable the assessment of integrated water management strategies, encompassing aspects of urban water systems, industrial processes, and agricultural practices. By considering the interconnectedness of various sectors, holistic approaches to water resource management can be formulated, promoting resilience and sustainability in the face of changing environmental conditions. The integration of chemical engineering simulations into the framework of the circular water economy offers a promising avenue for advancing sustainable water management practices. Through comprehensive modeling and analysis, informed decision-making can pave the way towards a more resilient and equitable water future, ensuring the long-term viability of our environmental systems.

Characterizations of a functionalized disused plastic-derived membrane and investigation of the effects of process variables on its adsorptive uptake of Pb2+ from simulated effluent using response surface methodology

This work focuses on the characterization and performance of the adsorptive membrane produced (via blending) functionalized waste polyethylene water sachets bags (PESWAB) with biopolymers. An adsorptive membrane (5.0 µm pore size) and (2.0 mm thickness) was fabricated from 9.0 g wt composite of PESWAB, chitosan, and cellulose acetate in the corresponding ratios of 1:2:1. Zeta potential, FTIR, SEM/EDX, water contact angle, and TGA/DTA were used to characterize the membrane. Response surface methodology (RSM) was used to model the effects of process variables on the adsorptive uptake of Pb2+ from simulated effluent. The zeta potential was shown to be between −26 and −68 mV at a pH between 4.6 and 9.5. This indicates a good level of stability and adsorptive potential. A hyrophilic membrane was suggested by the low average water contact angle of 79.0°. The gradual decomposition of the membrane indicated that the membrane dope solution was homogeneous. The membrane proved to be a quick and efficient adsorbent for the removal of aqueous Pb2+, as evidenced by the adsorption efficiency (92.0 %) realized at an optimum time of 65 min. The optimization result demonstrated that the RSM predicted and validated removal efficiencies were 96.78 % and 93.95 %, respectively. The regression model's applicability is supported by a low coefficient of variation (0.095 %), a P-value (<0.0001), a high model F-value of 4921.15, and a coefficient of determination (R2) value of 0.9996.

Revealing the impact of membrane adsorption on phenol transmembrane mass transfer in aqueous-aqueous membrane extraction

Nanoparticle doping in membranes is an ideal strategy for improving performance of aqueous-aqueous membrane extraction (AAME). However, its derived adsorption has not been investigated regarding performance enhancement/deterioration of phenol transmembrane mass transfer they might bring, especially in porous membranes. Therefore, supercapacitor-activated carbon (YEC-8)-doped (>30 mg/g) and silica-doped membranes (<0.1 mg/g) only with differentiated adsorption capacity were prepared to identify adsorption impact on phenol extraction from saline-wastewater. Surprisingly, membrane adsorption significantly inhibited phenol transmembrane mass transfer regardless of adsorption saturation rather than enhancement as we hypothesized. Compared to PVDF membrane, extraction performance of silica-doped membrane decreased by 24.0% at 2 g/L phenol. For YEC-8-doped membrane, its extraction performance even decreased by 40%-50% when facing multiple phenol concentrations. These results stated the important role of volatilization-diffusion in phenol transmembrane mass transfer in comparison with solution-diffusion. Membrane characterization and Hagen-Poiseuille model analysis demonstrated that membrane pore complexity would induce partial performance degradation. DFT calculation further confirmed that adsorption of gaseous phenol (−1.7292 eV) within membrane pores was primary limiting step in transmembrane mass transfer. Overall, this study elucidates transmembrane mass transfer pathway, process, and mechanism of phenol in AAME with nanoparticle-doped porous membrane for the first time.

Investigation of hydrogen permeation through niobium membranes in contact with liquid lithium

In fusion devices, liquid lithium is increasingly employed as a plasma-facing material owing to high heat loads and neutron irradiation, as well as the necessity for impurity control in the plasma. Notably, addressing the retention of hydrogen and its isotopes deuterium and tritium is crucial for effective utilization of liquid lithium. To measure and control the hydrogen and deuterium content in liquid lithium, specialized permeation sensors and permeation extraction devices are essential. Consequently, there is a need for research on the permeation and diffusion of hydrogen in liquid lithium and permeable membranes. This paper introduces a model encompassing hydrogen adsorption, diffusion, and permeation in niobium membranes and liquid lithium. Experimental measurements of hydrogen adsorption in liquid lithium and hydrogen permeation in niobium membranes are presented. The scenarios are simulated using hydrogen transport module developed on COMSOL platform, resulting in a relatively good agreement with the experimental data.

A Novel 3D-Printed and Miniaturized Periodic Counter Current Chromatography System for Continuous Purification of Monoclonal Antibodies.

Continuous chromatography has emerged as one of the most attractive methods for protein purification. Establishing such systems involves installing several chromatographic units in series to enable continuous separation processes and reduce the cost of the production of expensive proteins and biopharmaceuticals (such as monoclonal antibodies). However, most of the established systems are bulky and plagued by high dead volume, which requires further optimization for improved separation procedures. In this article, we present a miniaturized periodic counter-current chromatography (PCCC) system, which is characterized by substantially reduced dead volume when compared to traditional chromatography setups. The PCCC device was fabricated by 3D printing, allowing for flexible design adjustments and rapid prototyping, and has great potential to be used for the screening of optimized chromatography conditions and protocols. The functionality of the 3D-printed device was demonstrated with respect to the capture and polishing steps during a monoclonal antibody purification process. Furthermore, this novel miniaturized system was successfully used for two different chromatography techniques (affinity and ion-exchange chromatography) and two different types of chromatographic units (columns and membrane adsorbers). This demonstrated versability underscores the flexibility of this kind of system and its potential for utilization in various chromatography applications, such as direct product capture from perfusion cell cultures.

Continuous multi-column capture of monoclonal antibodies with convective diffusive membrane adsorbers.

Downstream processing is the bottleneck in the continuous manufacturing of monoclonal antibodies (mAbs). To overcome throughput limitations, two different continuous processes with a novel convective diffusive protein A membrane adsorber (MA) were investigated: the rapid cycling parallel multi-column chromatography (RC-PMCC) process and the rapid cycling simulated moving bed (RC-BioSMB) process. First, breakthrough curve experiments were performed to investigate the influence of the flow rate on the mAb dynamic binding capacity and to calculate the duration of the loading steps. In addition, customized control software was developed for an automated MA exchange in case of pressure increase due to membrane fouling to enable robust, uninterrupted, and continuous processing. Both processes were performed for 4 days with 0.61 g L-1 mAb-containing filtrate and process performance, product purity, productivity, and buffer consumption were compared. The mAb was recovered with a yield of approximately 90% and productivities of 1010 g L-1 d-1 (RC-PMCC) and 574 g L-1 d-1 (RC-BioSMB). At the same time, high removal of process-related impurities was achieved with both processes, whereas the buffer consumption was lower for the RC-BioSMB process. Finally, the attainable productivity for perfusion bioreactors of different sizes with suitable MA sizes was calculated to demonstrate the potential to operate both processes on a manufacturing scale with bioreactor volumes of up to 2000 L.

Biomass-based mixed matrix membrane adsorbers for removal of creatinine in dialysate fluid

Dialysate fluid is a vital component in hemodialysis therapy. Processing and reusing spent dialysate in hemodialysis significantly reduces costs and produces environmentally friendly hemodialysis. In this research, mixed matrix membrane adsorbers (MMMAs), which have the potential to recycle spent dialysate, have been developed. MMMA is composed of cellulose acetate (CA)-based polymers synthesized from cellulose isolated from oil palm empty fruit bunches (OPEFB) and integrated with silica (Si) bio-adsorbent from rice husk ash waste. The membrane was cast using the phase inversion method to form MMMAs CA-Si. The MMMAs CA-Si has a porous structure with evenly distributed silica particles. The pristine CA membranes had swelling and porosity degrees of 38.89 % and 21.23 %, while the MMMAs CA-Si had swelling and porosity degrees of 41.43 % and 27.81 %, respectively. The pristine CA membrane had a clean water flux of 86.86 L/m2h, while the MMMAs CA-Si membrane had a 96.25 L/m2h clean water flux. The MMMAs CA-Si has a tensile strength of 15.89 (Kgf/mm2) and an elongation of 14.01 %. The pristine CA membrane had a creatinine adsorption capacity of 2.8 mg/g, while the CA-Si MMMAs membrane had a maximum adsorption capacity of 9.98 mg/g. The maximum adsorption capacity (qm) is 9.98 mg/g MMMAs, equivalent to 24.95 mg creatinine/g silica in MMMAs and the dissociation constant (Kd) value is 1.91 mg/L. Creatinine can be removed from the dialysate through a continuous flow dialysis process using MMMAs CA-Si with a total removal of 10.48 mg/g or above 66.45 %. Creatinine can also be filtered by cross-flow circulation, and the total creatinine removal is above 81.0 %. MMMAs CA-Si can be an alternative separation medium to remove creatinine in the dialysate.

Ganglioside GM1 Drives Hemin and Protoporphyrin Adsorption in Phospholipid Membranes: A Structural Study.

Monosialoganglioside (GM1), a ubiquitous component of lipid rafts, and hemin, an integral part of heme proteins such as hemoglobin, are essential to the cell membranes of brain neurons and erythrocyte red blood cells for regulating cellular communication and oxygen transport. Protoporphyrin IX (PPIX) and its derivative hemin, on the contrary, show significant cytotoxic effects when in excess causing hematological diseases, such as thalassemia, anemia, malaria, and neurodegeneration. However, the in-depth molecular etiology of their interactions with the cell membrane has so far been poorly understood. Herein, the structure of the polymer cushion-supported lipid bilayer (SLB) of the binary mixture of phospholipid and GM1 in the presence of PPIX and its derivative hemin has been investigated to predict the molecular interactions in model phospholipid membranes. A high-resolution synchrotron-based X-ray scattering technique has been employed to explore the out-of-plane structure of the assembly at different compositions and concentrations. The structural changes have been complemented with the isobaric changes in the mean molecular area obtained from the Langmuir monolayer isotherm to predict the additive-induced membrane condensation and fluidization. PPIX-induced fluidization of phospholipid SLB without GM1 was witnessed, which was reversed to condensation with 2-fold higher structural changes in the presence of GM1. A hemin concentration-dependent linear condensing effect was observed in the pristine SLB. The effect was significantly reduced, and the linearity was observed to be lost in the mixed SLB containing GM1. Our study shows that GM1 alters the interaction of hemin and PPIX with the membrane, which could be explained with the aid of hydrophobic and electrostatic interactions. Our study indicates favorable and unfavorable interactions of GM1 with PPIX and hemin, respectively, in the membrane. The observed structural changes in both SLB and the underlying polymer cushion layer lead to the proposal of a molecule-specific interaction model that can benefit the pharmaceutical industries specialized for drug designing. Our study potentially enriches our fundamental biophysical understanding of neurodegenerative diseases and drug-membrane interactions.

A Label‐Free Multitechnique Approach to Characterize the Interaction of Bioactive Compounds with Biomimetic Interfaces

Extensive research has been conducted on biomimetic interfaces mimicking the complex and diverse microenvironment of cell membranes to gain insights into bioactive compound interactions and membrane biophysics modulation. The present study proposes an innovative approach that combines five prospective label‐free methodologies (derivative spectroscopy, synchrotron small‐ and wide‐angle X‐Ray scattering, attenuated total reflection–Fourier‐transform infrared spectroscopy, quartz‐crystal microbalance with dissipation, and surface plasmon resonance) to showcase their synergistic capabilities and complementarity in investigating drug–membrane interactions. This multitechnique approach combines the real‐time monitoring of the adsorption process under continuous flow conditions with the steady‐state perspective of this process. As a proof of concept, the interaction of three bioactive compounds (caffeine, testosterone, and diclofenac) with two biomimetic membrane interfaces (multistacked lipid bilayers and supported lipid bilayers) mimicking the more ordered lipid transient phases, with and without cholesterol (lo and so), that are responsible for a variety of membrane‐associated biological activities, is investigated. The biophysical effects of the bioactives are discussed using complementary data from real‐time and steady‐state experiments, including membrane adsorption and distribution, predicted location, and induced changes in order and fluidity, encompassing bilayer thickness, hydration, and area per lipid molecule.

Selective adsorption in ion exchange membranes: The effect of solution ion composition on ion partitioning

Electrodialysis is a water desalination technology that enables selective separation of ions, making it a promising solution for sustainable water reuse. The selectivity of the process is mainly determined by the properties of ion exchange membranes that can vary depending on the composition of ions in water, such as water uptake and charge density. In this work, we studied selective adsorption of Na+ and K+ ions in various ion exchange membranes considering the effect of solution ion composition on membrane water volume fraction. For that purpose, we conducted membrane adsorption experiments using solutions with Na+ and K+ ions with different ion compositions including Li+, Ca2+ or Mg2+ ions at different concentrations (0.001 – 0.25 M). The experiments showed that with the total ion concentration and the amount of divalent ions in solution, the membrane water volume fraction decreases while the selective adsorption of the smaller (hydrated) K+ ions over the Na+ ions in the membrane increases. We developed a theoretical framework based on Boublik-Mansoori-Carnahan-Starling-Leland (BMCSL) theory to describe the effect of membrane water volume fraction on selective adsorption of the ions by including volumetric effects, such as size exclusion. The developed framework was used to describe ion partitioning results of the membrane adsorption experiments. In addition, the effect of solution ion composition on selective ion removal during electrodialysis operation was evaluated using experimental data and theoretical calculations. The results of this study show that considering volumetric effects can improve the ion partitioning description in ion exchange membranes for solutions with various ion compositions.

Enhanced removal of tetracycline by sandwich layer composite membrane based on the synergistic effect of photocatalysis and adsorption

Environmental pollution has become increasingly serious, especially the abuse of tetracycline (TC) antibiotics, which has brought serious problems to human life. Therefore, the residual TC in the environment has become an urgent problem to be solved. To improve the efficiency of TC wastewater purification and solve the problem of powder material recovery during photocatalysis, a sandwich layer photocatalytic composite membrane with catalytic/adsorption synergistic effect was prepared in this study. The first layer of the composite membrane is composed of a polyether sulfone (PES) membrane loaded with UiO-66-NH2/Bi2.15WO6 (UN/BWO) photocatalyst (named as UN/BWO@PES), the middle layer is a support layer composed of polyester/cotton fabric, and the lower layer is composed of a calcium alginate/diatomite (CA@DE) membrane with adsorption for TC. Under dark conditions, the rejection percentage of TC by sandwich composite membrane (M4.5 D0.02-3) can reach 50.81%, while under light conditions, the removal efficiency of TC by M4.5 D0.02-3 can reach 93.94%. Even after four cycles, the removal percentage of TC by M4.5 D0.02-3 can still reach 87.10%. Therefore, the visible light responsive photocatalytic composite membrane developed in this study has dual advantages of photocatalysis and membrane adsorption filtration, and has enormous application potential in wastewater treatment, which can minimize membrane pollution and improve the reusability of photocatalysts.

Biowaste-alkaline lignin and GO integrated polysulfone ultrafiltration membrane fabrication for Pb2+ and Eosin Y dye removal

The textile industry uses a variety of lead compounds, including lead acetate for textile dyeing, lead chloride for lead salt manufacture, and lead molybdate for pigments. Furthermore, Eosin Y, a water-soluble red dye, is commonly used in textile dyeing and ink production. The presence of Eosin Y dye and lead metal ions in textile industry effluents is prevalent. Integrating adsorbent nanofillers into the membrane matrix serves a dual purpose of membrane filtration and adsorption functionalities. In this study, Lignin/GO incorporated polysulfone composite membranes were fabricated with the phase inversion method and with PEG 6000 as a pore-forming agent. Zeta potential, pure water flux, mechanical strength, and hydrophilicity of the membranes were all improved by the integration of lignin and GO into the membrane matrix. Filtration operations were carried out using an aqueous solution containing both lead (Pb) and Eosin Y dye. Additionally, the influence of their electrostatic interactions on membrane fouling and the regeneration process was examined. The electrostatic interaction, specifically the linking effect between Pb2+ ions and negatively charged Eosin Y molecules, formed larger Eosin-Pb complexes. This led to an enhanced Pb2+ removal through membrane filtration. During the second filtration cycle, the membrane, comprising 0.75 wt% lignin and 0.75 wt% GO, achieved 100 % removal of Pb2+ ions and an 81 % rejection of Eosin Y. A Pb2+ adsorption study was conducted using the optimized lignin/GO membrane. The adsorption process was investigated through Langmuir and Freundlich isotherms exhibiting a superior fit and assured R2 values of 0.977 and 0.994, respectively. According to the isotherm data the adsorption process involves multilayer physisorption. The developed Lignin/GO-incorporated polysulfone composite membranes hold the promise for tackling issues in a variety of domains, including water treatment and biomedical applications, demonstrating versatility and ability to make positive impacts across industries.

Polyelectrolyte electrostatically self-assembled modified porous polyacrylonitrile nanofibers as adsorbents for anionic dye removal

Herein, we chose PAN with good sunlight and weather resistance and easy surface modification as the electrospinning material to prepare the PAN nanofiber membrane. Then the surface modification of the obtained PAN fiber membrane was carried out sequentially by alkali hydrolysis and acid neutralization to make the surface of the fiber membrane negatively charged. Finally, the positively charged polyelectrolyte PAH on the surface was selected as the functional material, and a simple and environmentally friendly electrostatic self-assembly method was adopted to modify the prepared PAN nanofiber membranes labeled as PAN@PAH. This treatment effectively increased the storage space and adsorption groups of the fiber membranes, which led to a significant increase in the removal ability of anionic dyes in wastewater. In particular, the PAN@PAH nanofiber membrane adsorbed 439.66 mg/g of methyl orange and 946.83 mg/g of Congo red, which showed better adsorption capacity than many other membranes reported in the literature. Moreover, the adsorption capacity of PAN@PAH remained at 90.19 % after eight adsorption-desorption cycles. The preparation method and modification strategy of this membrane adsorbent provides new ideas and methods for the removal of other anionic dyes.

Performance investigation on a self-powered microbial pollutant adsorption cell with N-LAC/PVDF cation exchange membrane

A high-efficiency, self-powered microbial pollutant adsorption cell with an N-LAC/PVDF cation exchange membrane was proposed to remove metal ions and organic dyes in high-salt wastewater. Nitrogen-doped alkali lignin (N-LAC) was synthesized using chitosan nanoparticles (CS) and alkali lignin (AL) using a blending method. The N-LAC/PVDF cation exchange membrane was prepared by chemically grafting polyvinylidene fluoride (PVDF). With modification, hydroxyl, carboxyl, carbonyl, and other hydrophilicity groups were introduced into the cation exchange membrane. The addition of N-LAC improved the membrane's hydrophilicity and adsorption capacity. FITR and SEM, respectively, characterized the surface morphology of the exchange membrane. The result showed that the contact angle reached 74.89° when the amount of N-LAC was 1 wt.%, and the desalination efficiency was 93.5 %, which increased by 70 %. The adsorption capacity of organic dye Pb and metal ion MB was 91 % and 94 %, respectively, showing an increase of 31.9 % and 43.5 %.