Membranes For Water Treatment Research Articles

PVDF@CoFe2O4 nanoconfined catalytic membrane for natural surface water treatment: Efficient NOM degradation and membrane fouling mitigation

PVDF@CoFe2O4 nanoconfined catalytic membrane for natural surface water treatment: Efficient NOM degradation and membrane fouling mitigation

Energy-efficient Methods for Controlling Biofouling in Water Treatment Membranes and Future Directions

This paper aims to address the critical issue of biofouling in water treatment membrane systems, which decreases operational efficiency and increases energy consumption. The study explores energy-efficient biofouling control methods, focusing on established and emerging technologies. The review examines various approaches, including surface modification, antimicrobial nanomaterials, and photocatalytic membranes. Techniques using zwitterionic polymers, amphiphilic coatings, silver nanoparticles (nAg), and nanodiamonds (UDD) are analyzed for their effectiveness in mitigating biofouling. Photocatalytic membranes employing Metal-Organic Frameworks (MOFs) are also evaluated for their sustainable microbial inhibition capabilities. Surface modification techniques demonstrated the potential to alter membrane hydrophilicity, effectively preventing microbial adhesion and biofilm formation. Incorporating antimicrobial nanomaterials such as nAg and UDD disrupted microbial cell membranes and enhanced hydrophilicity, significantly increasing biofouling resistance. Photocatalytic membranes utilizing MOFs produced reactive oxygen species (ROS) under light exposure, providing a sustainable and energy-efficient approach to biofouling control. However, the integration of real-time monitoring systems and AI-based predictive models remains necessary to further optimize membrane performance and reduce energy consumption. The development of multifunctional membranes that combine biofouling resistance with resource recovery capabilities is essential to tackle the global water crisis and ensure access to clean water. Continued research in integrating advanced technologies such as AI and sustainable materials will be pivotal in advancing energy-efficient biofouling control.

Fluorinated silica/PCTFE nanocomposite membrane for water treatment using DCMD process

Fluorinated silica/PCTFE nanocomposite membrane for water treatment using DCMD process

Versatile Gas-Transfer Membrane in Water and Wastewater Treatment: Principles, Opportunities, and Challenges

Versatile Gas-Transfer Membrane in Water and Wastewater Treatment: Principles, Opportunities, and Challenges

Copper nanoparticles incorporated membranes for comprehensive treatment of surface water: synthesis and characterization

Copper nanoparticles incorporated membranes for comprehensive treatment of surface water: synthesis and characterization

Photothermal materials and membranes for solar-driven water treatment

Photothermal materials and membranes for solar-driven water treatment

Electroconductive membrane for water treatment: A new paradigm for accessing clean water

Electroconductive membrane for water treatment: A new paradigm for accessing clean water

Enhancing performance in gravity-driven membrane systems through pre-coating with aluminum-based flocs: Mechanism and energy saving analysis.

The gravity-driven membrane (GDM) system is an energy-efficient and environmentally sustainable water purification process; however, after prolonged operation, its membrane flux remains relatively low, making it necessary to adopt effective strategies for improving system performance. In this study, the effects of hydrostatic pressure (60, 100, 200mbar) and pre-coating with aluminum-based flocs (ABF) on GDM flux and organic matter removal were investigated, and the regulatory mechanisms of the bio-cake layer were explored through interactions between morphological structure, composition and microbes. The results showed that the stable flux of the GDM-ABF system at a hydrostatic pressure of 60mbar was almost equal to that at 100mbar, and it outperformed higher hydrostatic pressure in organic matter removal, resulting in a more porous bio-cake layer structure. GDM-ABF system at 60mbar achieved 38.51% energy saving compared to that at 100mbar. Increased hydrostatic pressure led to a denser biofouling layer and higher EPS concentrations, whereas pre-coating reduced the EPS concentration and resulted in a looser biofouling layer. Hydrostatic stress and pre-coating determined membrane fouling by regulating microbial communities and key metabolites. Increasing hydrostatic pressure down-regulated arginine and proline metabolism and aggravated membrane fouling, while pre-coating ABF up-regulated arginine and proline metabolism, down-regulated galactose metabolism, and alleviated the membrane fouling. Hydrostatic stress and pre-coating altered the abundance of keystone species involved in extracellular polymeric substances (EPS) formation within the bio-cake layer. Pre-coating with ABF at low hydrostatic pressure can achieve stable flux and effective water purification in GDM systems, similar to high hydrostatic pressure conditions, with the added benefits of being more environmentally friendly and low-carbon. This study proposes a strategy to balance flux and energy consumption in GDM systems, providing theoretical and technical support for the efficient application of GDM technology in membrane water treatment processes.

Interfacial Constructing Poly(ionic liquids) on Nanoporous Block Copolymers for Antifouling Ultrafiltration.

The remarkable flexibility in structural tunability and designability of poly(ionic liquids) (PILs) has garnered significant attention. Integration of PILs with membranes, novel properties, and functionalities is anticipated for applications in the fields of membrane separation. Here, we develop a facile method to prepare PIL-functionalized membranes in a one-step process by combining selective swelling-induced pore generation and ionic liquid functionalization. The block copolymer of poly(2-dimethylaminoethyl methacrylate)-block-polystyrene (PDMAEMA-b-PS, abbreviated as SDMA) films is immersed in a mixture of ethanol and bromopropane. In addition to the formation of nanoporous structures, an interfacial quaternization reaction between the PDMAEMA blocks and bromopropane occurs to generate poly(methacrylatoethyl propyl dimethylammonium bromide), resulting in the PIL-Br-functionalized membrane (SIL-Br) during the swelling process. It is noteworthy that bromopropane acting as a reactant also promotes the process of selective swelling. The water permeability of the resulting SIL-Br membrane is several times higher than that of the SDMA membrane, which is attributed to the increased pore size and significantly higher hydrophilicity of the SIL-Br membrane. In addition, the anion exchange of SIL-Br with l-proline (l-Pro) readily forms SIL-Pro-functionalized membranes (SIL-Pro), which exhibit exceptional electrical neutrality. Antifouling tests demonstrate that both SIL-Br and SIL-Pro have excellent resistance to proteins compared to the non-PIL-functionalization SDMA membrane, implying their great potential as antifouling membranes for water treatment.

Active Polymers Decorated with Major Acid Groups for Water Treatment: Potentials and Challenges.

Polymers exhibiting ion-conduction capabilities are essential components of water-purifying devices. These polymers not only transport selective ions but are also mechanically robust; thus, they can be processed as membranes. In this review, we highlight major acidic polymers and their engineered morphologies and optimized properties, including metal selectivity and water permeation or retention. Crucial phenomena, such as self-assembly in acid-group-functionalized polymers for driving water transportation, are discussed. It was observed that the phosphonic acid groups containing polymers are rather suitable for the selective adsorption of toxic metals, and thus, are superior to their sulfonated counterparts. Additionally, due to their amphoteric nature, phosphonated polymers displayed several modes of metal complexations, which makes them appropriate for eliminating a wide range of metals. Further observation indicates that aromatic-acid-functionalized polymers are more durable. Temperature- and pH-responsive polymers were also found to be promising candidates for a controlled water-treatment process. Nevertheless, considering the morphology, water retention, and metal adsorption, acid-functionalized polymers, especially phosphonated ones, have the potential to remain as the materials of choice after additional advancements. Further perspectives regarding improvements in acidic polymers and their fabricated membranes for water treatment are presented.

Characterization and Disinfection Performance of α-Fe2O3-TiO2 Based Polyester Membranes for Water Treatment

Water is essential for life; however, many people in developing countries, particularly in rural areas, lack access to clean and safe piped water. Lack of appropriate water treatment makes such people to consume untreated water containing biological and chemical pollutants, leading to diseases and even death. Hence, developing eco-friendly technologies using available resources can help address this critical issue. In this study α-Fe2O3-TiO2 coated polyester membranes were employed the disinfection of water containing Escherichia coli (E. coli) as an indicator microorganism. The coated and uncoated membranes were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD). Antibacterial studies were done through direct contact with bacteria (glass bottle test) and the flow test under sunlight irradiation at various initial bacterial concentrations (2.45 × 103 to 2.45 × 105 CFU/mL). SEM images revealed the presence of the photocatalyst within the membranes, and EDX confirmed the successful impregnation through component analysis. A clear inhibition zone was observed around the coated membranes, 19 and 17 mm for 2.45 × 103 and 2.45 × 105 CFU/mL, respectively, and no inhibition zone was observed around the uncoated membranes. The coated membranes achieved disinfection efficiency of 91.3% in the glass bottle test and 98.30% in the flow test under sun light irradiation. The novelty of the study is that α-Fe2O3-TiO2 impregnated photocatalytic membranes demonstrated excellent disinfection efficacy compared to the uncoated membranes and can readily be applied for water purification in areas that lack centralized water treatment systems.

Synthesis of polyamide-based RO membranes for saline water treatment

Reverse osmosis (RO) technology is a widely used method for converting seawater into fresh water, known for its high efficiency and broad applications. This study focuses on optimizing the synthesis conditions for polyamide (PA) membranes, including the concentrations of m-phenylenediamine (MPD) and trimesoyl chloride (TMC), the choice of solvent, soaking time, and reaction time. FTIR and SEM analysis confirmed the successful synthesis of the PA layer and revealed that the surface morphology of the membrane was significantly influenced by synthesis conditions. Mechanical testing demonstrated that the optimized membranes exhibited high tensile strength (41.18 MPa) and low elongation at break (11.69%), indicating a robust but relatively brittle material. The study determined that the optimal conditions were 1.0 wt.% MPD and 0.1 wt.% TMC, hexane as a solvent, a soaking time of 2 min, and a reaction time of 60 sec, achieving a maximum salt rejection of 86.45%. These findings are critical for enhancing RO membrane efficiency and addressing the global demand for clean water.

Crosslinked chitosan-modified ultrafiltration membranes for efficient surface water treatment and enhanced anti-fouling performances

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Asymmetric Membranes Obtained from Sulfonated HIPS Waste with Potential Application in Wastewater Treatment.

The recovery and reuse of high-impact polystyrene (HIPS) into high-value products is crucial for reducing environmental thermoplastics waste and promoting sustainable materials for various applications. In this study, asymmetric membranes obtained from sulfonated HIPS waste were used for salt and dye removals. The incorporation of sulfonic acid (-SO3H) groups into HIPS waste by direct chemical sulfonation with chlorosulfonic acid (CSA), at two different concentrations, was investigated to impart antifouling properties in membranes for water treatment. Asymmetric membranes from recycled HIPS, R-HIPS, R-HIPS-3, and R-HIPS-5 with 3 and 5% sulfonation degrees, respectively. Sulfonated HIPS shows a decrease in water contact angle (WCA) from 83.8° for recycled R-HIPS to 66.1° for R-HIPS-5, respectively. A WCA decrease leads to an increase in antifouling properties for R-HIPS-5, compared to non-sulfonated R-HIPS, which leads to a higher flux recovery ratio (FRR) and enhanced separation properties for sulfonated membranes. The HIPS-5 membrane exhibited the highest rejection rates for Reactive Black 5 dye (94%) and divalent salts (72% for MgSO4 and 67% for Na2SO4). The performance of the recycled HIPS asymmetric membranes is well correlated with porosity, water uptake, and the higher negative charge from the sulfonic acid groups present, which enhance the electrostatic repulsions of salts and dyes.

Analysis of Metal-Organic Framework and Polyamide Interfaces in Membranes for Water Treatment and Antibacterial Applications.

Integrating biocidal nanoparticles (NPs) into polyamide (PA) membranes shows promise for enhancing resistance to biofouling. Incorporating techniques can tailor thin-film nanocomposite (TFN) membranes for specific water purification applications. In this study, silver-based metal-organic framework Ag-MOFs (using silver nitrate and 1,3,5-benzentricarboxylic acid as precursors) are incorporated into PA membranes via three different methods: i) incorporation, ii) dip-coating, and iii) in situ ultrasonic techniques. The characterizations, such as top-surface and cross-section scanning and transmission microscopy, reveal that the incorporation methods for the modified TFN membranes substantially control morphology and surface characteristics. For example, the in situ ultrasonically interlayered Ag-MOFs showed the largest pores (average pore diameter of 14 Å ± 0.1), resulting in the highest water permeance (water flux of 10.9 LMH/bar for Na2SO4). It also show superior antifouling and anti-biofouling performance, with a flux recovery ratio (FRR) of 94.1% in both fouling tests due to its improved surface hydrophilicity and the antibacterial properties of incorporated Ag-MOFs. Conversely, the surface-grafted dip-coated Ag-MOFs offered the highest salt rejection, attributed to its highly negatively charged surface and a dense PA network with narrow pores (average pore diameter of 10 Å ± 0.06).

Electrochemically Assisted Cobalt/MXene Membrane for Effective Water Treatment: Synchronously Improving Catalytic Performance and Anti-Interference Ability.

Catalytic membrane technology for water treatment is often constrained by a trade-off between permeability and catalytic efficiency as well as interference from coexisting anions and organic matter in natural water matrices. Herein, a novel cobalt-loaded MXene (Co/MXene) 2D membrane with good hydrophilicity, electrical conductivity, and PMS activation function is constructed. The negative voltage is exerted on the membrane to significantly enhance its PMS activation efficiency and anti-interference capacity toward effective water treatment. Under -2 V, the optimal Co/MXene catalytic membrane displays 100% rhodamine b (RhB) removal within a residence time of only 1.1 s, whose RhB degradation kinetic constant (k of 6.85 s-1) is 17.6 times higher than that of the Co/MXene catalytic membrane alone and is also greatly superior to other advanced catalysts and catalytic membranes. Meanwhile, the catalytic membrane displays obvious anti-interference ability in the presence of various coexisting substances of the water matrix and performs well in treating the secondary effluent of coking wastewater. The radical-dominated (SO4•- and •OH) mechanism accompanied by the nonradical species (1O2 and Co(VI)═O) is revealed in the system, and the reactive species production is obviously enhanced under negative voltage. Experimental results and theoretical calculations jointly confirm the key role of electrochemical assistance in enhancing membrane performance, which not only facilitates cycling of Co3+/Co2+ for enhanced PMS activation via improving PMS adsorption and promoting charge transfer from Co to PMS but also hinders interference from coexisting substances in water via electrostatic repulsion.

Insight Into the Role of Fiber Diameter on Electrospun Polysulfone Mats

ABSTRACTFiber electrospun mats created using cylindrical collectors have been extensively studied as effective membranes for water treatment. However, the relationships between the properties of electrospun mats and the characteristics and performance of membranes are not well‐established. This research examined two samples with average fiber diameters of 1.8 ± 0.49 μm and 0.47 ± 0.26 μm, which were evaluated as supporting substrates for the separation of MgSO4 ions. The variation in fiber diameter resulted from consistent conditions of voltage, distance, and collector rotation speed, while the injection rates were different, set at 2 mL/h and 0.8 mL/h, respectively. The resulting thin‐film composite (TFC) membrane consists of three layers: the first layer is a mesh polyester that underlies a middle hydrophobic electrospun support layer made from a 20 wt.% polysulfone solution. The third layer is a polyamide layer created through interfacial polymerization, involving a reaction between piperazine (PIP) monomers at a concentration of 2% by weight and trimesoyl chloride (TMC) monomers at a concentration of 0.2% by weight. Due to its hydrophobic nature, PSU repels water monomers from its surface during polymerization. Consequently, surface modification using plasma treatment alters the surface characteristics from hydrophobic to hydrophilic, resulting in the formation of a superior polyamide layer. The results indicate that membranes with larger fiber diameters exhibit a rougher texture. Additionally, the increased void space between the fibers in these membranes leads to an increase in pure water flux that is 92% higher compared to membrane samples with smaller fiber diameters; this higher flux is due to larger pore size. Furthermore, membranes with smaller fiber diameters possess a finer pore structure, resulting in a polyamide layer with fewer defects than membranes with larger fibers. This improved structure achieved a separation efficiency of 68% ± 1.02% for MgSO4, while the membrane with an average fiber diameter of 1.80 ± 0.49 μm demonstrated a separation rate of 20% ± 2.26%. These findings provide a step forward in the development of a theoretical framework for engineering TFC membranes with electrospun mats as supports.

Dual-layer coated photocatalytic membranes for surface water treatment: Insight of membrane fouling restriction

The combination of carbon-based material adsorption and photocatalytic oxidation is a crucial approach to eliminate natural organic substances and mitigate membrane fouling induced by them. In this investigation, Bi2O3-TiO2 (BT) was incorporated with three varieties of carbon-based substances (such as powdered activated carbon (PAC), ordered mesoporous carbon CMK-3 (OMCs), and carbon nanotubes (CNTs)) and employed as a dual-layer coating on the surface of the ultrafiltration membrane to reduce membrane fouling induced by natural organics during the treatment of actual water bodies. Under light conditions, the BT/CMK-3 coating outperforms BT/PAC and BT/CNTs coatings in reducing membrane fouling, with a flux recovery rate of up to 80.4 % and an irreversible fouling rate as low as 19.5 %, while also improving the removal rates of UV254 and DOC to 55.2 % and 77.9 %, respectively. Based on the analyses of three-dimensional fluorescence PARAFAC and liquid chromatography, the BT/CMK-3 coating efficiently removes humic substances and protein-like compounds via adsorption and photocatalytic oxidation, achieving a 24.1 % removal rate of humic acid and a 93.7 % removal rate of low molecular weight neutral substances. Under the synergy of CMK-3 adsorption and BT photocatalytic oxidation, reactive oxygen species effectively degraded and transformed the membrane foulants enriched by CMK-3, reducing and increasing the Zeta potential and free energy on the membrane surface to −4.2 mV and 15.1mJ/m2, respectively. The interaction force between the foulant and the membrane changed into a repulsive force, and the fouling mechanism changed from complete blockage to intermediate blockage, thereby shortening the transition time. This advancement provides significant promise for the development and broader application of photocatalytic membrane filtration technology.

Oxygen vacancies-enriched spent lithium-ion battery cathode materials loaded catalytic membrane for effective peracetic acid activation and organic pollutants degradation

Advanced oxidation processes combined with membrane filtration technique offer a promising approach for pollution mitigation and catalyst recovery. Herein, a waste ternary lithium-ion battery cathode material of LiNixCoyMnzO2 (LNCM) loaded polytetrafluoroethylene (PTFE) membrane was synthesized for peracetic acid (PAA) activation (LNCM-PTFE/PAA) and 2,4,6-trichlorophenol (TCP) degradation. Such a novel membrane, with a catalyst loading of 10 mg (0.796 mg/cm2) of LNCM achieved 96.4 % removal of TCP (2 mg/L) within 20 min in neutral pH. The redox cycles of surface metals (such as Co3+/Co2+, Ni3+/Ni2+, and Mn4+/Mn3+/Mn2+) in spent LNCM efficiently enhance charge transfer and mediated PAA activation. And intrinsic oxygen vacancies in LNCM facilitated PAA adsorption and its cleavage. The resulting carbon-centered radicals (R-C•, CH3C(O)OO•) and 1O2 are identified as the primary reactive species that collaboratively participate in TCP degradation. Quantitative structure-activity relationship analysis demonstrated a substantial reduction in product toxicity. The successful practical application of the LNCM-PTFE/PAA membrane was exemplified by treating chlorophenol industrial wastewater. This study presents a new LNCM-PTFE/PAA catalytic membrane for high-efficiency water treatment and a novel perspective for green utilization of waste LNCM.

High performance composite hollow fiber nanofiltration membrane fabricated via the synergistic effect of co-solvent assisted interfacial polymerization and macrocyclic polyamine incorporation

The necessity for high-performance thin film composite (TFC) nanofiltration (NF) membranes for drinking water and wastewater treatment is becoming increasingly apparent in the face of the global water crisis. In this work, co-solvent (acetone) assisted interfacial polymerization (CAIP) and incorporating macrocyclic polyamine (Cyclen) as an aqueous co-monomer were employed to fabricate hollow fiber (HF) NF membrane and to enhance the permeability and the selectivity, respectively, thereby overcoming the inherent trade-off effect. The effects of Cyclen and acetone on the separation performance were comprehensively investigated, and the interfacial polymerization conditions were optimized. The optimal HF NF membrane exhibits a 68.6 % increment in water permeance relative to the baseline membrane while without sacrificing the Na2SO4 rejection which is as high as 99.2 %. In particular, it exhibits a superior high pure water permeability of 222.5 L m−2 h−1 MPa−1, ranking among the highest observed for HF NF membranes in the existing literature. Moreover, it exhibits excellent acid resistance as well as fouling resistance. This research paves a novel approach for developing high-performance HF NF membranes for water and wastewater treatment.