Membrane Adsorption Research Articles

Highly nanostructured and carboxylated wood aerogel-based adsorption membrane reconstructed by grafting of polyacrylic acid for efficient removal of heavy-metal ions

A highly nanostructured and carboxylated WA-PAA1.5 membrane was developed to remove heavy-metal ions from wastewater depended on wood nanotechnology and reconstruction of nanostructure by the grafting of polyacrylic acid (PAA). The combination of delignification and 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-mediated −oxidation treatment transformed the bulk wood into wood aerogel with a microfibril network in the cell wall, providing abundant active hydroxyl sites. As a result, the PAA polymer was efficiently grafted onto cell wall and filled in the vessel and intercellular space, which reconstructed a highly nanostructured WA-PAA1.5 membrane with rich carboxyl groups (6.5 mmol/g). Correspondingly, the WA-PAA1.5 membrane manifested a superior adsorption capacity for Cu2+, Pb2+, Cd2+, and Ni2+, which was around 248 mg/g, 268 mg/g, 255 mg/g and 276 mg/g, respectively. These values were significantly higher than most biomass-based adsorption materials due to the synergistic effect of the enhanced carboxyl groups and the reconstructed mesoporous structure. The adsorption mechanism investigation proved the chemical linkage between the carboxyl groups and Cu2+ in wastewater. Meanwhile, the WA-PAA1.5 membrane also displayed excellent recycle performance, in which the removal efficiency of Cu2+ still remained above 85 % after undergoing eight cycles. Furthermore, the multi-layer WA-PAA1.5 filtration device demonstrated exceptional removal efficiency for a variety of heavy-metal ions, indicating the availability in practical wastewater treatment. The prepared WA-PAA1.5 membrane in this study has promising potential to replace the present plastic-based materials for the removal of heavy-metal ions in wastewater because of the facile technology, high removal efficient and sustainability, as well as biodegradability.

An Adsorptive Membrane Platform for Precision Ion Separation: Membrane Design and First‐Principles Studies

One of the key challenges in separation science is the lack of precise ion separation methods and mechanistic understanding crucial for efficiently recovering critical materials from complex aqueous matrices. Herein, first‐principles electronic structure calculations and in situ Raman spectroscopy are studied to elucidate the factors governing ion discrimination in an adsorptive membrane specifically designed for transition metal ion separation. Density functional theory calculations and in situ Raman data jointly reveal the thermodynamically favorable binding preferences and detailed adsorption mechanisms for competing ions. How membrane binding preferences correlate with the electronic properties of ligands is explored, such as orbital hybridization and electron localization. The findings underscore the importance of the phenolate group in oxime ligands for achieving high selectivity among competing transition metal ions. In‐depth understanding on which specific atomistic site within the microenvironment of metal‐ligand binding pockets governs the ion discrimination behaviors of the host will build a solid foundation to guide the rational design of next‐generation materials for precision separation essential for energy technologies and environment remediation. In tandem, synthetic controllability is demonstrated to transform 3D micrometer‐scale crystals to a 2D crystalline selective layer in membranes, paving the way for more precise and sustainable advances in separation science.

Membrane-Based Pulsed Sampling Method for Extended Dynamic Range of Ion Mobility Spectrometry.

Ion mobility spectrometry (IMS) has been widely studied and applied as an effective analytical technology for the on-site detection of volatile organic compounds (VOCs). Despite its superior selectivity compared with most gas sensors, its limited dynamic range is regarded as a major drawback, limiting its further application in quantitative measurements. In this work, we proposed a novel sample introduction method based on pulsed membrane adsorption, which effectively enhanced IMS's ability to measure analytes at higher concentrations. Taking N-methyl-2-pyrrolidone (NMP) as an example, this new sampling method expanded the dynamic range from 1 ppm to 200 ppm. The working principle and measurement strategy of this sampling method were also discussed, providing new insights for the design and application of IMS-based instruments.

Electrostatic Spinning to Construct Al/Fe-MOF/PAN Nanofibrous Membranes for the Selective Adsorption of Se(IV) in Water

Electrostatic Spinning to Construct Al/Fe-MOF/PAN Nanofibrous Membranes for the Selective Adsorption of Se(IV) in Water

Construction of a Multiscaled Synergistic Membrane for Efficient Dye Adsorption and Emulsion Separation

Construction of a Multiscaled Synergistic Membrane for Efficient Dye Adsorption and Emulsion Separation

A Short Review of Advances in MOF Glass Membranes for Gas Adsorption and Separation.

The phenomenon of melting in metal-organic frameworks (MOFs) has recently garnered attention. Crystalline MOF materials can be transformed into an amorphous glassy state through melt-quenching treatment. The resulting MOF glass structure eliminates grain boundaries and retains short-range order while exhibiting long-range disorder. Based on these properties, it emerges as a promising candidate for high-performance separation membranes. MOF glass membranes exhibit permanent and accessible porosity, allowing for selective adsorption of different gas species. This review summarizes the melting mechanism of MOFs and explores the impact of ligands and metal ions on glassy MOFs. Additionally, it presents an analysis of the diverse classes of MOF glass composites, outlining their structures and properties, which are conducive to gas adsorption and separation. The absence of inter-crystalline defects in the structures, coupled with their distinctive mechanical properties, renders them highly promising for industrial gas separation applications. Furthermore, this review provides a summary of recent research on MOF glass composite membranes for gas adsorption and separation. It also addresses the challenges associated with membrane production and suggests future research directions.

Effective uranium extraction from seawater through immobilization of conjugated microporous polymers on collagen fiber membrane

Extracting uranium from seawater has become an important method to supplement the nuclear industry. Herein, we introduce a simple route to load conjugated microporous polymers onto collagen fiber membranes, resulting in a novel membrane adsorbent material (CMPA-F/CFM) for uranium capture. Its Langmuir adsorption capacity reaches 304.9 mg·g−1 (at 318 K), with fast adsorption kinetic of 60 min, and excellent adsorption selectivity with Kd = 4.69 × 104 mL·g−1 under the temperature of 298 K, initial concentration of 50 mg·L-1, and pH = 7, thus allowing a satisfactory adsorption performance in a 7-day real ocean experiment with a uranium adsorption capacity of 1.25 mg·g−1. Furthermore, in continuous dynamic adsorption experiments, CMPA-F/CFM could treat up to 19.0 L·g−1 of low-enriched uranium (LEU) solution (1 mg·L-1), with a uranium removal rate of up to 87.5 % (10 L of seawater). This study demonstrates broad potential application of membrane adsorption in extraction of low-enriched uranium.

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.