Membrane Separation Research Articles

Screening of the biphenyl polyamides nanofilms appropriate for molecular separation in organic solution feed

Developing polymeric separation membranes that combine excellent solvent stability, high permeability, and customizable molecular weight interception remains a challenge. Herein, thin-film composite (TFC) polyamide (PA) membranes with poly(ether ether ketone) (PEEK) support and biphenyl-centered polyamides active layer were fabricated through interfacial polymerization technique for the first time. Enhanced solvent stability was exhibited by the fabricated membranes due to the intrinsic resistance to organic solvents possessed by PEEK and biphenyl polyamides. The separation performance of the obtained membranes was systematically studied by relating to the properties of PA nanofilms in terms of nano-mechanical strength, morphologies, and microporosity. The organic solvent nanofiltration (OSN) performance of the resultant membranes in terms of permeability and molecular weight cut-off (MWCO) could be regulated. The optimized membrane exhibited a pure solvent permeability as high as 21.6 L m−2 h−1 bar−1 for acetonitrile and 14.0 L m−2 h−1 bar−1 for methanol. It also showed excellent long-term durability with almost unchanged permeability as well as solute retention remained above 97.8 % after a cumulative OSN operation of N, N-Dimethylformamide (DMF) based feed for 240 h. In particular, OSN membrane with targeted MWCOs covering the range of 170–370 g·mol−1 could be fabricated by selecting appropriate biphenyl acyl chlorides as building blocks. This approach offers a scalable and versatile platform for the development of solvent-stable, highly permeable, and customizable MWCO membranes for process-oriented OSN.

Anti-biofouling membrane coated with polyvinyl alcohol/sodium carboxymethylcellulose/tannic acid hydrogel for efficient dye/salt separation

Biofouling is the most severe challenge for separation membranes. In this study, a metal-organic framework (MOF)-based mixed-matrix membranes (MMMs) with polyvinyl alcohol (PVA)/sodium carboxymethylcellulose (CMC)/tannic acid (TA) hydrogel coating exhibited a comprehensive anti-biofouling property and high efficient for dye/salt separation. For the hydrogel layer, ethanol inhibited the cross-linking of the hydrogen bond between the PVA, CMC and TA, forming a uniform “hydrogel paint” applied to the membrane surface using the coating method. Subsequently, the hydrogen bond was re-established by evaporating the ethanol. The hydrogel coating could form a dense hydrated layer, endowing the membrane with excellent anti-fouling properties, including oil, proteins, and bacteria. For the MOF-based MMMs layer, the skeleton structure of polyvinylidene fluoride anchored the bimetallic MOF crystals to mitigate the phenomenon of “trade-off”. The hydrogel-coated MOF-based MMMs showed excellent properties, such as the water permeability was ~200 Lm−2 h−1, the rejection for Reactive Blue 19 was 100 %, the rejection for NaCl was 10.9 %, and it showed excellent stability for long-term service. Furthermore, the hydrogel-coated MOF-based MMMs presented a significant inhibitory effect on surface bacteria growth. In brief, this paper provided a new insight into preparing hydrogel-coated MOF-based MMMs, which had potential applications in separating dye/salt.

In situ microbubble-mediated strategy for highly efficient anti-crude oil-fouling membrane with parallel nanosheet structure

Membrane fouling caused by highly viscous oils severely hampers the long-term application of oil–water separation membranes. In situ aeration, achieved by applying a voltage to the membrane to produce bubbles, can effectively reduce the adhesion of oil contaminants. Herein, the parallel NiFe-layered double hydroxide arrays were successfully constructed on Ni foam using a hydrothermal method. Compared with NF@NFLDH having randomly aligned nanosheet arrays, NF@NFLDH-P can produce more numerous micro-size bubbles. A substantial number of the microbubbles spontaneously coalesced with oil droplets, and the synergy of buoyancy and kinetic energy significantly hindered oil fouling on the NF@NFLDH-P membrane. Specifically, this microbubble–mediated anti-oil-fouling strategy substantially reduced the flux attenuation and maintained a high flux recovery ratio during long-term crude oil–water separation, exhibiting a great operational life. This study suggests an innovative way to design future anti-fouling membranes with bubble-mediated capabilities.

Diffusive nature of different gases in graphite: Implications for gas separation membrane technology

Graphite membranes have gained attention in membrane technology for gas separation due to their high stiffness, strength, and stability in corrosive and high-temperature environments. Graphite exists naturally in geologic media and can also be prepared by synthetic processes. In- situ hydrogen (H2) production in petroleum reservoirs or H2 storage in depleted gas reservoirs results in contamination with CH4 and CO2. To address the separation challenge at the surface, a sustainable downhole wellbore membrane must be available to separate H2, leaving behind CO2 and other gases to improve operational economics. Currently, there are no studies in the literature on the self-diffusivity of gases (CO2, H2, and CH4) in graphite as a function of pore size. To overcome time constraints in diffusivity experiments, this work utilized mathematical models and molecular simulations to delineate the self-diffusivity of gases in graphite of different pore sizes.To acknowledge subsurface operational conditions during in situ hydrogen production, we considered a temperature of 360 K and a wide pressure spectrum from 2 MPa to 20 MPa. In this study, we explored the diffusive nature of H2, CH4, and CO2 gases in different nanopore-sized graphite using analytical and molecular simulation approaches. We validated the results by presenting unrestricted case density calculations. First, effective diffusivity was calculated using the mean free pore path, followed by gas adsorption at high pressures (10–20 MPa) and a temperature of 350 K. The study utilized theoretical models and molecular dynamics (MD) simulations to determine the self-diffusivity of gases in graphite systems with various structures.

Long-lived superhydrophobic micro/nano-locked fiber membranes for long-lasting oil-water separation effectiveness

Superhydrophobic/superoleophilic oil-water separation membranes have great potential for treating industrial, domestic, and marine oily wastewater. However, the robustness of these membranes remains a challenge that restricts their ability to maintain long-lasting oil-water separation effectiveness. Inspired by the adhesion mechanisms of snail and tree frog, exploiting the synergistic effects of interfacial hydrogen bonding and mechanical interlocking, we herein achieved strong adhesion between hydrophobicized in-situ nanoparticles and textile fibers to fabricate a long-lived superhydrophobic micro/nano-locked fiber membrane (LSMFM). LSMFM maintains excellent superhydrophobicity even when exposed to mechanical and chemical damage, such as continuous sandpaper abrasion, tape-peeling, weight impact, water jet, and acid/alkali/salt erosion. Additionally, LSMFM efficiently separates various light/heavy oil-water mixtures, achieving a remarkable separation flux of >10,000 L·m−2·h−1 and an efficiency >98 %, even after 200 cycles with n-hexane. Importantly, such membranes still maintain a high separation flux >19,000 L·m−2·h−1 and efficiency >97 % after sequentially being subjected to acids, alkalis, freezing, and high temperatures, and even the adsorption bag formed by wrapping LSMFM with superhydrophilic wood pulp cotton can adsorb oil at fixed-point and continuously recover pure oil from oily wastewater. This study paves a new way for the sustainable purification of oily wastewater in extreme environments.

3D Covalent Organic Framework Membranes for Molecular Separations.

Membrane separation has become an indispensable separation technology in social production, playing an important role in drug production, water purification, etc. The key core of membranes lies in achieving efficient and precise sieving between substances. As a result, a typical trade-off arises: highly permeable membranes usually sacrifice selectivity and vice versa. To address this dilemma, long-term research has focused on comprehensive understanding and modelling of synthetic membranes at various scales. A significant advancement in this arena is the advent of three-dimensional covalent organic framework (3D COF) membranes, a novel category of long-range ordered porous organic polymer materials. Characterized by an abundance of interconnected channels, diverse pore wall properties, tunable structures, and robust thermal and chemical resilience, 3D COF membranes offer a promising approach for efficient substance separation. This review undertakes a meticulous investigation of the synthesis and physicochemical properties of 3D COF membranes, accentuating the underlying design principles, fabrication methods, and application attempts. A comprehensive assessment of their research trajectory and current standing in the field of membrane processes is provided. The review culminates in a forward-looking outlook, summarizing future research directions and highlighting the substantial potential of this innovative work to shape the future of efficient membrane separation processes.

Mixed dimensional assembly of biodegradable and antifouling wood-based covalent organic framework composite membranes for rapid and efficient dye/salt separation

Manipulating materials of different dimensions into heterogeneous nanofiltration membranes with unique physicochemical properties and molecular sieving channels provides an effective way for accurate and fast molecular separation. Here we introduce a heterogeneous structure hybrid connection strategy to fabricate biodegradable wood-based covalent organic framework (COF) composite membranes. As a proof of concept, 3D Picea jezoensis (Siebold & Zucc.) Carrière was selected as the substrate of the membrane and in situ growth of 2D iCOF selective layers. Effective modulation of iCOF layers by 1D sulfonated polyaryletherketone (SPEEK-Na) using the “needle and thread” method. The rearrangement of the above multidimensional materials formed charge-regulated properties of laminar nano-channels and smooth hydrophilic contact area, thereby endowing specific molecular transport pathways and sieving capability for efficient dye/salt separation under ultra-low pressure of 0.5 bar. The wood-based heterostructured membranes exhibited high dye rejection (>97 %), low salt rejection (<10 %), and high permeance (172.34 L m−2 h−1 bar−1), which is superior to many reported dye/salt separation membrane materials. In addition, the system exhibited a certain degree of operational stability, good antifouling, and soil biodegradability. Overall, this work enables the design and fabrication of heterostructured separation membranes to be obtained from nature and used in nature, resulting in efficient and sustainable water purification applications.

In situ hydrolyzed microporous polymer membranes for additional free volume to facilitate CO2 permeation

Advancements in membrane separation technology play a pivotal role in separation processes closely associated with the environment and energy. However, presently available commercial polymeric membranes encounter the challenge of low permeability, impacting both separation efficiency and membrane module costs. Here, we propose a simple and effective in situ acid hydrolysis strategy to significantly enhance membrane permeability. Specifically, a tetrafluorinated monomer with hydrolyzable Schiff base groups (TFNAD) has been meticulously designed, synthesized, and copolymerized with commercial TFTPN and TTSBI, yielding a series of copolymers. Subsequently, in situ hydrolysis removes aniline from the membrane, freeing up the occupied free volume and creating additional channels for gas transport. This process substantially enhances gas permeability while preserving the desired selectivity. PIM-TFAD-30 showed a 68 % improvement in CO2 permeability with virtually no compromise in CO2/N2 selectivity compared to the pre-hydrolysis membrane. Meanwhile, PIM-TFAD-30 also displayed outstanding separation performance and plasticization resistance in simulated flue gas tests, demonstrating its potential for practical application. This facile and straightforward hydrolysis method opens up a new perspective for preparing and modifying polymeric separation membranes beyond gas separation.

Modelling across Multiple Scales to Design Biopolymer Membranes for Sustainable Gas Separations: 2-Multiscale Approach

The majority of materials used for membrane-based separation of gas mixtures are non-renewable and non-biodegradable, and the assessment of alternative bio-based polymers requires expensive and time-consuming experimental campaigns. This effort can be reduced by adopting suitable modelling approaches. In this series of works, we propose various modelling approaches to assess the CO2/CH4 separation performance of eight different copolymers of 3-hydroxybutyrate and 3-hydroxyvalerate (PHBV) using a limited amount of experimental data for model calibration. In part 1, we adopted a fully atomistic approach based on Molecular Dynamics (MD), while, in this work, we propose a multiscale methodology where a molecular description of the polymers is bridged to a macroscopic prediction of its gas sorption behaviour. PHBV structures were simulated using MD to obtain pressure–volume–temperature data, which were used to parametrise the Sanchez–Lacombe Equation of State. This, in turn, allows for the evaluation of the CO2 and CH4 solubility in the copolymers at various pressures and compositions with little computational effort, enabling the estimate of the sorption-based selectivity. The gas separation performance obtained with this multiscale technique was compared to results obtained with a fully atomistic model and experimental data. The solubility–selectivity for the CO2/CH4 mixture is in reasonable agreement between the two models and the experimental data. The multiscale method presented is a time-efficient alternative to fully atomistic methods and detailed experimental campaigns and can accelerate the introduction of renewable materials in different applications.

Poly(vinylidene fluoride)/Nickel Oxide–Montmorillonite Mixed-Matrix Membranes for Oil Separation from Emulsified Oily Wastewater

Poly(vinylidene fluoride)/Nickel Oxide–Montmorillonite Mixed-Matrix Membranes for Oil Separation from Emulsified Oily Wastewater

Investigation into the Simulation and Mechanisms of Metal-Organic Framework Membrane for Natural Gas Dehydration.

Natural gas dehydration is a critical process in natural gas extraction and transportation, and the membrane separation method is the most suitable technology for gas dehydration. In this paper, based on molecular dynamics theory, we investigate the performance of a metal-organic composite membrane (ZIF-90 membrane) in natural gas dehydration. The paper elucidates the adsorption, diffusion, permeation, and separation mechanisms of water and methane with the ZIF-90 membrane, and clarifies the influence of temperature on gas separation. The results show that (1) the diffusion energy barrier and pore size are the primary factors in achieving the separation of water and methane. The diffusion energy barriers for the two molecules (CH4 and H2O) are ΔE(CH4) = 155.5 meV and ΔE(H2O) = 50.1 meV, respectively. (2) The ZIF-90 is more selective of H2O, which is mainly due to the strong interaction between the H2O molecule and the polar functional groups (such as aldehyde groups) within the ZIF-90. (3) A higher temperature accelerates the gas separation process. The higher the temperature is, the faster the separation process is. (4) The pore radius is identified as the intrinsic mechanism enabling the separation of water and methane in ZIF-90 membranes.

Application of Polymeric Tubular Ultrafiltration Membranes for Separation of Car Wash Wastewater.

The commercial ultrafiltration tubular polyvinylidene fluoride (PVDF) (100 and 200 kDa) and polyethersulfone (PES) (4 kDa) membranes were applied for filtration of car wash wastewater. Intensive fouling was noticed, which caused an over 50% flux reduction during 3-5 h of the filtration process. This phenomenon was reduced by washing the membranes with an alkaline cleaning agent (pH = 11.5), which is used in car washes to remove insects. The filtration/membrane washing cycle was repeated many times to achieve stable operation of the membrane modules. It has been found that cyclic repeated washing did not deteriorate the performance of the membranes. Despite frequent cleaning of the membranes (every 5-7 h), irreversible fouling occurred, resulting in a 20% reduction in the initial permeate flux. However, the formation of a filter cake definitely improved the separation degree and, for the 200 kDa membranes, separation of the wastewater components was obtained as it was for the 4 kDa membranes, while, at the same time, the permeate flux was 5 times higher.

Innovative Trends in Modified Membranes: A Mini Review of Applications and Challenges in the Food Sector.

Membrane technologies play a pivotal role in various industrial sectors, including food processing. Membranes act as barriers, selectively allowing the passage of one or other types of species. The separation processes that involve them offer advantages such as continuity, energy efficiency, compactness of devices, operational simplicity, and minimal consumption of chemical reagents. The efficiency of membrane separation depends on various factors, such as morphology, composition, and process parameters. Fouling, a significant limitation in membrane processes, leads to a decline in performance over time. Anti-fouling strategies involve adjustments to process parameters or direct modifications to the membrane, aiming to enhance efficiency. Recent research has focused on mitigating fouling, particularly in the food industry, where complex organic streams pose challenges. Membrane processes address consumer demands for natural and healthy products, contributing to new formulations with antioxidant properties. These trends align with environmental concerns, emphasizing sustainable practices. Despite numerous works on membrane modification, a research gap exists, especially with regard to the application of modified membranes in the food industry. This review aims to systematize information on modified membranes, providing insights into their practical application. This comprehensive overview covers membrane modification methods, fouling mechanisms, and distinct applications in the food sector. This study highlights the potential of modified membranes for specific tasks in the food industry and encourages further research in this promising field.

Ultrahydrophilic Inorganic Nanosheet-Based Nanofiltration Membranes for High Efficiency Separations of Inorganic Salts and Organic Dyes.

Two-dimensional (2D) inorganic nanomaterials have garnered extensive attention in the fabrication of inorganic nanofiltration membranes due to their unique structures and properties. In this study, we developed a facile process for fabricating large-scale ultrahydrophilic nanofiltration membranes using layered titanate H1.07Ti1.73O4·nH2O nanosheets (HT-ns). A drying deposition process was used to fabricate HT-ns membranes on a poly(tetrafluoroethylene) (TF) substrate. To enhance the bonding strength between the substrate and the deposited HT-ns membrane, the substrate surface was modified with a Cu2+-adsorbed silane monomolecular layer, connecting a negatively charged HT-ns membrane and a positively charged substrate surface. The fabricated HT-ns membrane exhibited an excellent rejection performance for inorganic salts and dye molecules. The ultrahydrophilicity of HT-ns membrane with a low water contact angle of 31° results in an ultrafast water permeance, which is approximately 6 times higher than that of a simple graphene-based nanofiltration membrane. The results open a new avenue to a new category of ultrahydrophilic nanofiltration membranes.

Swelling-assisted surface grafting strategy for multichannel antifouling membranes: Reconstruction of surface pore structure and applications in microalgae harvesting and blood purification

Membrane fouling remains a major challenge in membrane separation. The modification of hydrophilic membrane surfaces can mitigate irreversible fouling deposition, thereby improving antifouling properties. Effective surface modification strategies are essential techniques for developing highly efficient antifouling membranes. In this work, a swelling-assisted surface grafting strategy was proposed for multichannel antifouling membranes, where various lengths of polyvinylpyrrolidone (PVP) brushes were grafted on the surface of polysulfone membrane using reversible addition-fragmentation chain transfer polymerization. The successful grafting of PVP polymer brushes was confirmed using Fourier transform infrared spectrometer and X-ray Photoelectron Spectroscopy. Changes in membrane morphology and pore structure were observed via scanning electron microscope and atomic force microscope. During the grafting process, the amphiphilic macromolecules formed through grafting were selectively swelled by graft solvent, leading to the formation of mesopores in both the surface layer and sublayer of the membrane, which formed additional water transport channels. The introduction of hydrophilic polymer brushes and the change of pore structure significantly boosted the hydrophilicity and permeability of the membranes. As a result, the water contact angle decreased from 85° to 42°, accompanied by an approximate 3.24-fold increase in pure water flux (PWF). Due to superior hydrophilicity, modified membranes demonstrated exemplary performance in microalgae harvesting, boasting a microalgae retention rate nearing 100 % and low fouling resistance (2.12 × 1012 m−1). In algal filtration experiments, a confocal laser scanning microscope was employed to assess the activity of filtered algae on the membrane surface. The prepared membranes effectively maintained the bioactivity of algae while also achieving a high flux recovery rate (90.7 %) following filtration and cleaning. Furthermore, in blood cell compatibility tests, the modified membranes exhibited resistance to blood cell adhesion and sustained a low hemolysis rate (0.06 %). Overall, this strategy offers unique insights into the fabrication of antifouling surfaces and shows considerable promise for large-scale applications in microalgae harvesting and blood purification.

Highly plasticization-resistant Tröger’s base polymer–MOF mixed-matrix membranes for stable gas separation

The plasticization phenomenon, characterized by polymer chain swelling when exposed to highly soluble gas at high feed pressure, has been a major problem for polymer membranes. To address this, we prepared Tröger’s base (TB) polymer-based metal–organic framework (MOF) mixed-matrix membranes (MMMs), which are highly plasticization-resistant membranes. Three different highly porous MOF nanoparticles (ZIF-8, UiO-66-NH2, and MIL-101(Cr)) were prepared in small particle sizes. The corresponding MMMs were formed with a 30 wt% MOF loading to study the effects of MOF species, particle size, chemical functionality, and MOF–polymer interfacial interaction on gas-transport properties and plasticization behavior. The TB polymer-based MOF MMMs exhibited significantly higher H2 and CO2 permeabilities (fourfold to eightfold) than the TB polymer membrane owing to the porous nature and high gas adsorption capacity of the MOF. Additionally, the TB-based MOF MMMs, particularly the UiO-66-NH2 MMM, displayed exceptional CO2 plasticization resistance. This is attributed to the interfacial interaction of the strong hydrogen bonding between the amine group of the TB polymer and the amino group of UiO-66-NH2, as confirmed by small-angle X-ray scattering characterization. This TB polymer-based MOF MMM approach provides a feasible and effective route for enhancing gas-transport properties and CO2 plasticization resistance to achieve energy-efficient and stable gas separation.

NiO nanosheets constructing honeycomb porous catalyst as an effective oxygen adsorption interlayer support for high performance lithium-oxygen batteries

Lithium-oxygen (LiO2) batteries are considered as a novel energy storage system as a result of its outstanding energy density. However, the challenge of oxygen corrosion is still restricting the practical application in LiO2 batteries. Here, we successfully acquire the NiO nanosheets constructing honeycomb porous catalysts as an effective oxygen adsorption interlayer support for high-performance LiO2 batteries. Honeycomb porous structures can store more oxygen and the defects in the exterior of NiO nanosheets can furnish more Lewis acid sites and catalytic sites to bind more O2− as a Lewis base for absorbing O2. Consequently, NiO nanosheets constructing honeycomb porous catalysts as interlayer is loading on the glass fiber membrane separator for LiO2 batteries in order to protect the anode from oxygen corrosion. The interlayer with 1.0 mg/cm2 NiO loading rate per unit area shows the outstanding electrochemical performance at a fixed 500 mAh/g specific discharge capacity and 0.1 mA/cm2 current density for 106 cycles in the LiO2 battery. This work provides an effective strategy to protect the Li metal anode in LiO2 batteries, at the same time, proposes a novel view for the efficient modification of separator.

Fabrication of a ZIF-8/PVA Membrane on PVDF Fiber by Spray for the Highly Efficient Separation of Oil-in-Water Emulsions.

In human life and production, excessive oily wastewaters containing detergents are produced and discharged, causing severe environmental pollution and water resource problems. A metal-organic framework (MOF)-based membrane is an economical and environmentally friendly tool for emulsion separation but is limited by a complex preparation process and poor flexibility. Herein, we developed a simple method to synthesize a MOF-based mixed-matrix membrane (MMM) by spray and fabricated the membrane on poly(vinylidene fluoride) (PVDF) fibers via postdeposition and in situ growth manners. The prepared ZIF-8/PVA MMMs have uniform distribution of ZIF-8 particles and poly(vinyl alcohol) (PVA) on the PVDF fibers. PVA improved the adhesion between the ZIF-8 particles and between the MOF layer and PVDF fiber, endowing the separation membrane with high flexibility and bendability. The prepared ZIF-8/PVA membrane exhibited hydrophilicity and underwater superoleophobicity, which showed high separation efficiency and considerable water flux for emulsions, emulsion containing dye, and surfactant-stabilized emulsion. In addition, the fabricated ZIF-8/PVA/PVDF fibers exhibited good antifouling property and flexibility and can maintain stable separation efficiency after working several times and even under bending, demonstrating the stability and potentiality of the ZIF-8/PVA/PVDF fibers in practical applications. This work paves a new avenue for the synthesis and application of MOF-based MMMs.

Nickel-cobalt hydrogen phosphate membrane with outstanding anti-crude oil-fouling capability and its microscopic anti-fouling mechanism

Oil/water separation membranes with superior anti-fouling properties against highly viscous oils are crucial for the efficient treatment of oily wastewater. Herein, the effects of functional groups in an inorganic superhydrophilic membrane on the anti-fouling properties of the membrane are investigated. Using a facile one-step electrochemical deposition method, Ni1-xCoxHPO4·3H2O membranes were formed on a Cu(OH)2 microneedle-coated copper mesh (CCNC–P) with superhydrophilic and underwater superoleophobic properties. All CCNC–P membranes with different Co2+ contents showed outstanding anti-fouling capability for oily wastewater such as those containing crude oil. The CCNC–P(x = 0.5) membrane exhibited high separation efficiency reaching 99.7 % across five oil–water mixtures and oil-in-water emulsions, concurrently presenting an ultrahigh flux of 61695 L m−2 h−1 for crude oil–water mixture. Moreover, the membrane consistently maintained its separation performance during the long-term crude oil–water separation process. The flux decline ratio was below 1 %, and the flux recovery ratio approached 99.4 %. The CCNC–P membranes possessed superior chemical, thermal, and mechanical stability, suggesting significant potential for the industrial treatment of oily wastewater. Density functional theory calculation revealed that the HPO42− group in CCNC–P can strongly adsorb water molecules. The resultant stabilized hydration layer impeded the contact between the membrane surface and oil droplets, while the metal ions scarcely influenced the adsorption of water molecules on CCNC–P. These findings provide new insights into the development of novel oil–water separation membranes with higher anti-fouling capabilities against high-viscosity oils.

PREPARATION AND CHARACTERIZATION OF POLYMER INCLUSION MEMBRANES BASED ON BIODEGRADABLE CELLULOSE/ALGERIAN CLAY FOR HEAVY METALS REMOVAL FROM WASTEWATER

Separation membranes have gained attention as promising options for water and wastewater treatment due to their financial sustainability, and eco-friendliness. However, practical challenges have limited their application in water separation. To overcome these limitations, inorganic-organic hybrid membranes have been developed in this study. The present work deals with two attractive aspects: (i) economical, through the valorization of a local clay (Algerian kaolin), and (ii) environmental, which is based on the membrane selectivity for metal ions. The principal objective of this work is the development of enhanced nanocomposite membranes. It is achieved with low costs, based on cellulose triacetate (CTA) as a polymeric matrix modified by the addition of a lamellar filler, i.e. yellow clay obtained from Jijel, located in the east of Algeria, and plasticized by dioctyl phthalate (DOP). A further objective of this paper was the treatment of wastewater polluted by lead (Pb2+) and cadmium (Cd2+). The prepared membranes were characterized by various characterization techniques, including scanning electron microscopy (SEM), Fourier-transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). All synthetized membranes had an amorphous structure, with homogeneous pore morphology and distribution. Moreover, the presence of nanocomposite clay showed effective integration into the membrane matrix and led to a significant improvement in thermal resistance. These membranes were applied to treat a synthetic aqueous solution contaminated with heavy metals, namely Pb2+ and Cd2+. The results revealed a rejection rate higher than 50%, suggesting the potential effectiveness of a stable and environmentally sustainable polymer inclusion membrane system for water purification.