Search Results (601)

Transition metal carbides/nitrides (MXenes) nanosheets have emerged as promising candidates for constructing high-performance nanofiltration (NF) membranes for separation processes. However, MXene membranes exhibit limited feasibility due to the instability of their microstructure, which can lead to failure in the filtration process. This study presents a bridging strategy (polyethyleneimine and polydopamine) to prepare a stable titanium carbide (Ti₃C₂) membrane, resulting in superior nanofiltration efficiency. Polyethyleneimine intercalation can inhibit the tendency to swell, while polydopamine enhances the force between the substrate and nanosheets. The optimized membrane possesses a permeate flux of 112.3 L m⁻² h⁻¹ bar⁻¹ (1.6 times higher than pristine Ti₃C₂ membrane) and good selectivity (methyl blue rejection rate: ~99.5%; Na₂SO₄ rejection rate: <5.0%). In addition, the prepared membrane has good long-time durability and is more suitable for low pressure nanofiltration. Notably, the bridging strategy is also applicable to various two-dimensional lamellar membranes. This strategy provides a universal method for enhancing the stability of two-dimensional membranes, thereby promoting their practical applications in robust separation processes. Full article

Thin-film composite nanofiltration membranes were fabricated via the interfacial polymerization method from optimized polyethersulfone (PES) mixed matrix membranes, using m-phenylenediamine and trimesoyl chloride monomers, which produced a selective polyamide layer and were used for heavy metal removal. The concentration of trimesoyl chloride (TMC) is a critical factor to govern the properties of the selective polyamide layer, which directly influences the surface morphology and selective performance of (0.5 wt%) PES-coreshell-Fe₃O₄/ZnO membranes. Morphological structure, illustrated by SEM images, elucidated the role of TMC addition. FTIR spectra validated the successful formation of the amine and acyl chloride groups. Performance studies illustrated that NF3 (made from 0.1 w/v% of TMC) showed a unique salt rejection trend (NaCl > Na₂SO₄ > MgCl₂) with an optimal salt rejection of 52.64%, 50.91%, and 12.67%. A low concentration of 0.1 w/v% of the NF3 membrane was the most optimal high-performance membrane. The adsorption rate of NF3 for Pb(II) ions in real environmental wastewater is attributed to the tailored surface chemistry of the polyamide layered thin-film/PES-coreshell-Fe₃O₄/ZnO nanocomposites of the membranes. The maximum Langmuir adsorption capacity at the optimal pH = 5 was 8.8573 mg/g at 25 °C. The fabricated adsorptive nanofiltration membranes alleviated the presence of Pb(II) ions and other competing ions present in environmental wastewater. Full article

The valorization of wood vinegar from biomass pyrolysis has been a significant research subject in recent years, but further studies to reduce its phytotoxicity and improve agricultural applications are still needed. This study investigates the application of ultrafiltration and nanofiltration membranes in treating the wood vinegar from grape pomace pyrolysis, aiming to valorize it. Wood vinegar treated with nanofiltration (NF270 membrane) and diluted 100 times acted as a root growth inducer in cucumber seeds, achieving a germination index of 145%. This interesting result suggests that nanofiltration is emerging as a promising technology for enhancing the value of wood vinegar, while also promoting sustainability and the circular economy in the agro-industrial sector. Full article

With the growing interest in fabricating nanofiltration membranes using novel materials and techniques, there is an increasing need to evaluate the practical viability of innovative membranes at the early stages of development. In many materials research laboratories, access to professionally manufactured membrane-evaluation systems may be limited. Here we present a pressure-driven filtration system for evaluation of nanofiltration membranes, which can be constructed from 3D-printed parts and widely available off-the-shelf components at a cost of approximately 60 €. The system uses a stirred cross-flow design capable of circulating the feed solution in the filter cell and maintaining a stable solute concentration during extended filtration experiments—as in conventional cross-flow cells. It is suitable for the filtration of aqueous solutions containing dyes, inorganic salts, and dilute acids. Validation was performed by filtering a 2000 mg L⁻¹ MgSO₄ solution through a Veolia RL membrane at 7.6 bar, achieving a 96.5% rejection rate and a permeance of 7.5 L m⁻² h⁻¹ bar⁻¹ after 24 h of continuous operation. Full article

Seawater desalination has emerged as a crucial solution for addressing global freshwater scarcity. However, it generates significant volumes of concentrated brine waste. This brine is rich in dissolved salts and minerals, primarily, chloride (55%), sodium (30%), sulfate (8%), magnesium (4%), calcium (1%), potassium (1%), bicarbonate (0.4%), and bromide (0.2%), which are often discharged into marine environments, posing ecological challenges. This study presents a comprehensive global review of innovative technologies for recovering these constituents as valuable products, thereby enhancing the sustainability and economic viability of desalination. The paper evaluates a range of proven and emerging recovery methods, including membrane separation, nanofiltration, electrodialysis, thermal crystallization, solar evaporation, chemical precipitation, and electrochemical extraction. Each technique is analyzed for its effectiveness in isolating salts (NaCl, KCl, and CaSO₄) and minerals (Mg(OH)₂ and Br₂), with a discussion of process-specific constraints, recovery efficiencies, and product purities. Furthermore, the study incorporates a detailed techno-economic assessment, highlighting revenue potential, capital and operational expenditures, and breakeven timelines. Simulated case studies of a 100,000 m³/day seawater reverse osmosis (SWRO) facility demonstrates that a sequential brine recovery process and associated energy balances, supported by pilot-scale data from ongoing global initiatives, can achieve over 90% total salt recovery while producing marketable products such as NaCl, Mg(OH)₂, and Br₂. The estimated revenue from recovered materials ranges between USD 4.5 and 6.8 million per year, offsetting 65–90% of annual desalination operating costs. The analysis indicates a payback period of 3–5 years, depending on recovery efficiency and product pricing, underscoring the economic viability of large-scale brine valorization alongside its environmental benefits. By transforming waste brine into a source of commercial commodities, desalination facilities can move toward circular economy models and achieve greater sustainability. A practical integration framework is proposed for both new and existing SWRO plants, with a focus on aligning with the principles of a circular economy. By transforming waste brine into a resource stream for commercial products, desalination facilities can reduce environmental discharge and generate additional revenue. The study concludes with actionable recommendations and insights to guide policymakers, engineers, and investors in advancing brine mining toward full-scale implementation. Full article

The effects of pretreatment pH value, operating pressure, and concentration factors on the performance of nanofiltration membrane concentration and the recovery of phosphorus-containing wastewater were systematically studied. A novel pretreatment strategy using solid sodium hydroxide was developed to adjust the feed solution pH, achieving optimal solid removal and minimized conductivity at pH = 5. Unlike conventional calcium-based methods, this approach avoids excessive chemical sludge formation and mitigates membrane scaling, enhancing system stability. Experimental results demonstrate that both phosphorus rejection and desalination efficiency are significantly influenced by feed solution pH, operating pressure, and concentration ratio. While increasing pH and pressure improve total phosphorus (TP) rejection and desalination rates, these benefits are accompanied by reduced membrane flux due to elevated osmotic pressure and intensified concentration polarization. The membrane exhibited optimal performance at a feed pH of 5 and an operating pressure of 3 MPa, with sustained flux and enhanced separation efficiency. Under these conditions, when the wastewater was concentrated fivefold at 25 °C, the TP rejection rate and desalination efficiency reached 92.9% and 91.8%, respectively. Full article

Membrane technology offers considerable potential for enhancing or partially replacing conventional separation techniques, which could eventually lead to substantial energy savings. This review focuses on recent advancements in membrane separation technologies including organic solvent pervaporation (OSPV), organic solvent reverse osmosis (OSRO), organic solvent nanofiltration (OSN), and organic solvent ultrafiltration (OSUF) that are increasingly vital in the pharmaceutical, biochemical, and petrochemical industries. Although hybrid and inorganic membranes exhibit promising performance, polymeric membranes provide advantages in scalability and processability. The development of materials capable of operating under demanding conditions that include exposure to organic solvents, high temperatures, extreme pH levels, and oxidative environments remains critical. Here, we examine recent innovations in membrane materials and their integration into organic solvent systems. Key challenges, including material swelling, fouling, and scaling, are discussed, along with recent strategies to address these issues. Finally, we identify emerging research directions that could drive further progress in membrane technology for organic media applications. Full article

Tobacco extract contains numerous valuable components, among which nicotine possesses significant potential for high-value applications despite its well-known health risks. However, the efficient extraction of nicotine is challenging due to the complex composition of tobacco extracts and the limitations of conventional separation techniques. In this work, an integrally asymmetric nanofiltration membrane was developed via thermal cross-linking for highly efficient nicotine separation. A poly(aryl ether ketone) (PEK)-based ultrafiltration membrane was first prepared via non-solvent induced phase separation (NIPS), followed by controlled thermal cross-linking to tailor the membrane pore size toward the molecular weight of nicotine. To mitigate pore collapse and enhance flux, TiO₂ nanoparticles were incorporated in situ through a sol–gel method. The resulting thermally cross-linked membrane exhibited a molecular weight cut-off of ~180 Da, a nicotine rejection rate of 93.2%, and a permeation flux of 143 L/(m²·h)—representing a 259% increase over the control membrane. Moreover, the thermally cross-linked membranes demonstrated exceptional chemical stability in various organic solvents and extreme pH conditions. This work offers a feasible and sustainable strategy for fabric high-performance nanofiltration membranes for the targeted extraction of bioactive molecules from complex plant extracts. Full article

Brick tea is a type of post-fermented food that involves microorganisms. Long-term consumption of brick tea exposes consumers to high fluoride levels, which can adversely affect their health. This study explored the feasibility of selective defluorination of Qingzhuan brick tea through membrane separation technology, and pilot production was conducted to produce defluorinated instant brick tea. The concentration of tea polyphenols increased by more than 10 times after nanofiltration, demonstrating the high selectivity of nanofiltration membranes toward fluoride. Defluorination trends were studied at different initial material concentrations (0.5–4%) and operating pressures (0.1–0.5 MPa) under cyclic defluorination. Defluorinated instant brick tea products were also industrially prepared using 300- (DF-300) and 1000-Da (DF-1000) membranes, followed by vacuum freeze-drying. The DF-1000 and DF-300 products exhibited a defluorination rate of 51.46% and 67.96%, respectively. The products have excellent characteristics in terms of color, aroma, and flavor quality, as well as solubility. Gas chromatography–mass spectrometry indicated that the volatile components in the defluorinated instant brick tea were slightly different from those in the original tea, but the key aroma and flavor characteristics of the defluorinated brick tea remained unchanged. Membrane separation provides technical support for the large-scale production of low-fluoride post-fermented tea. Full article

Following on from a circular economy in water, membrane technologies can play a role in resource recovery and high-quality water production but should also consider membrane industry circularity. Anaerobic membrane bioreactors (AnMBRs) are being used for advanced wastewater treatment, and their applications are growing due to advantages like lower sludge volume, better permeate quality, and the generation of biogas. High-Rejection (HR) AnMBRs retain a higher fraction of dissolved and particulate components to further promote resource recovery and obtain improved effluent quality. With the development of membrane technologies, end-of-life (EOL) membrane recycling is emerging for various applications. The feasibility of transforming EOL Reverse Osmosis (RO) membranes into ultrafiltration (UF)- and nanofiltration (NF)-like membranes and applying these membranes to submerged HR-AnMBR applications was evaluated. A small pilot AnMBR with granular biomass was operated with EOL RO membranes converted to submerged UF- and NF-like membranes and compared to commercial microfiltration (MF) membranes. UF- and NF-like plates were constructed, characterized, and introduced step-by-step into the AnMBR by the substitution of MF plates. A chemical oxygen demand (COD) removal study showed that while 77% removal of COD was possible with MF membranes, improved COD removal (i.e., 81.40% and 88.39%) was achieved using UF-like and NF-like membranes, respectively. Because of the higher retention of salts of the NF-like membrane, the salinity in the membrane bioreactor increased from 1300 to 1680 µS·cm⁻¹ but stabilized quickly and without a negative impact on system performance. Even without cleaning, minimal fouling and flux decline were observed for all tested configurations thanks to the use of granular biomass and low permeation flux. Permeate flux in the case of the NF-like membrane was slightly lower due to the required higher pressure. The present study demonstrated that the EOL-RO membranes may find applications in HR-AnMBRs to achieve superior permeate quality and move toward circular membrane processes. Full article

Landfill is a source of environmental concern as it may contaminate surface and groundwater, which could be a major source of potable water supply. Reverse osmosis (RO) membrane treatment is a well-known technique for treating leachate, but it requires high pressures of 80 bars or more to function. In addition, pretreatment, scaling, biofouling and concentrate disposal bring additional challenges to RO operation. The use of nanofiltration (NF) membranes with low rejection ensures the concentrate is separated into organic and salt solutions at a low pressure of 16–18 bars and ensures the concentrate volume is reduced to less than 3% of its initial value. This results in a reduction in energy consumption by a factor of least three compared to using conventional high-pressure RO, which reduces the initial leachate amount to 9–10%, and evaporation results in a subsequent reduction in concentrate volume to 3–4 per cent of the initial leachate volume. Due to the low osmotic pressure, the volume of an organic solution after separation can be reduced by three to four times compared to a saline solution of the same concentration. Full article

This study investigates the enhancement of polyvinylidene fluoride (PVDF) membranes with polyethylene glycol (PEG) to improve their efficacy in treating tofu wastewater through the ultrafiltration (UF) process. PVDF membranes with varying PEG concentrations of 0, 0.5, 1, and 1.5% in the dope solution were produced, characterized via FTIR, mechanical strength, porosity, and contact angle measurements, and evaluated in wastewater treatment at varying pressures of 3, 4, and 5 bar in the UF process. The incorporation of PEG increased the membrane’s porosity from 28.2% for M-0 to 43.5% for M-1.5. The contact angle decreased from 65.3° for M-0 to 53.3° for M-1.5, indicating an increase in hydrophilicity. Elongation increased from 36.0% for M-0 to 113.5% for M-1.5; however, the tensile strength decreased from 11.8 MPa for M-0 to 5.4 MPa for M-1.5. Although PEG-modified membranes demonstrated enhanced flux, with values of 6.3 L∙m⁻²∙h⁻¹ for M-0 and 15.7 L∙m⁻²∙h⁻¹ for M-1.5 at a pressure of 5 bar, pure PVDF membranes (M-0) showed greater rejection rates for chemical oxygen demand (COD), total dissolve solid (TDS), total suspended solid (TSS), and turbidity at 3 bar, achieving values of 66.3%, 41.6%, 99.6%, and 99.1%, respectively. Following ultrafiltration, the pH and TDS levels conformed to Indonesian government guidelines; however, the COD levels were non-compliant, indicating the need for additional treatment. The findings suggest that PVDF/PEG ultrafiltration membranes are suitable for pre-treatment; however, nanofiltrationor reverse osmosis may be necessary to meet the stringent regulatory standards for tofu wastewater treatment. The modified M-1.5 membrane is recommended as the primary ultrafiltration membrane for tofu wastewater treatment due to its superior flux, prior to nanofiltration or reverse osmosis, to comply with the stringent regulatory standards established by the Government of the Republic of Indonesia. Full article

Organic solvent nanofiltration (OSN) is a promising technology for solute removal from organic media, yet developing membranes with stable separation performance remains challenging. This study presents a solvent-resistant double-crosslinked nanofiltration membrane fabricated via a two-step strategy: preparation of the membrane by the polyion complexion reaction-assisted non-solvent-induced phase inversion (PIC-assisted NIPS) method and then post-crosslinking with hydrothermal treatment followed by quaternization with 1,3,5-tris(bromomethyl)benzene (TBB). To enhance solvent stability, molybdenum sulfide (MoS₂) nanosheets were incorporated into a hydrolyzed polyacrylonitrile (H-PAN) substrate. The H-PAN/MoS₂/PEI base membrane was fabricated by PIC-assisted NIPS with a polyethylenimine (PEI) aqueous solution as the coagulation bath. The membrane subsequently underwent dual crosslinking comprising hydrothermal treatment and 1,3,5-tris(bromomethyl)benzene (TBB)-mediated quaternization crosslinking, ultimately yielding the H-PAN/MoS₂/PEI (Ther.+TBB QCL) composite membrane. These crosslinking procedures reduced the membrane’s separation skin layer thickness from 64 nm (uncrosslinked) to 41 nm. The resultant membrane effectively separated dyes from ethanol, achieving a rejection rate of 97.0 ± 0.9% for anionic dyes (e.g., Congo Red) and a permeance flux of 23.6 ± 0.2 L·m⁻²·h⁻¹·bar⁻¹ at 0.4 MPa. Furthermore, after 30 days of immersion in ethanol at 25 °C, its flux decay rate was markedly lower than that of a non-crosslinked control membrane. The enhanced separation performance and stability are attributed to the thermal crosslinking promoting amide bond formation and the TBB crosslinking introducing quaternary ammonium groups. This double-crosslinking strategy offers a promising approach for preparing high-performance OSN membranes. Full article

Chitosan biopolymer membranes reinforced with channel-selective ZIF-8 nanofillers were developed and thoroughly characterized as separators for bioelectrochemical systems. This study explores the synergistic effect of incorporating ZIF-8 into a chitosan matrix to enhance membrane performance. Key properties including water retention, chemical and thermal stability, surface resistance, antifouling capacity, and ionic conductivity were evaluated and benchmarked against commercial Nafion-117 and nanofiltration (NF) membranes. The ZIF-8/chitosan composite membranes (ZIF-8/CS) demonstrated excellent water retention and structural stability under harsh conditions, along with significantly reduced surface resistance and effective rejection of organic contaminants and salts (NaCl, Na₂SO₄). Notably, the composite ZIF-8/CS membranes achieved an ionic conductivity of 0.099 S/cm, approaching the value of Nafion-117 (0.13 S/cm) and substantially surpassing that of the NF membrane (0.013 S/cm). These results indicate that ZIF-8-reinforced chitosan membranes present a promising, sustainable, and cost-effective alternative to traditional separators in bioelectrochemical applications. Full article

Developing efficient bio-based membranes is key to sustainable wastewater treatment, especially when they can be applied across multiple separation processes for components of varying molecular weights. This study reports the development and characterization of bio-based mixed matrix membranes from carboxymethyl cellulose (CMC) modified with synthesized carboxylated graphene oxide (GOCOOH), aimed at improving performance in both pervaporation and nanofiltration for water treatment. Membrane design was optimized by adjusting the GOCOOH content, applying chemical cross-linking (by immersing in glutaraldehyde with H₂SO₄), and developing highly effective supported membranes (by the deposition of a thin selective CMC-based layer onto a porous substrate). Comprehensive characterization was performed using spectroscopic, microscopic, and thermogravimetric analyses and contact angle measurements. The optimized cross-linked supported CMC/GOCOOH (5%) membrane demonstrated significantly improved transport properties: a 2.5-fold increased permeation flux and over 99.9 wt.% water in permeate in pervaporation dehydration of isopropanol, and high rejection rates—above 98.5% for anionic dyes and over 99.8% for heavy metal ions in nanofiltration. These findings demonstrate that CMC/GOCOOH membranes are promising, sustainable materials suitable for multiple separation processes involving components of varying molecular weights, contributing to more efficient and eco-friendly wastewater treatment solutions. Full article