Fabrication Of Nanofiltration Membranes Research Articles

Polyelectrolyte fabricated nanofiltration membrane with heterogeneously charged channels for high efficient cephalexin wastewater treatment

Nanofiltration (NF) for treatments of pharmaceutical wastewater is a promising direction for water protection and resources recovery. Herein, a novel membrane with heterogeneously charged channels was constructed by modified layer-by-layer assembly methods. Within the well-designed pores, the polyanion structure excludes the cephalexin and the cationic structure slows down its diffusion, thereby rejections for cephalexin are improved. The hydrophilic property of polyelectrolytes simultaneously guarantees the water transport. Fabricated heterogeneously charged channels are shown to strengthen the electrostatic barrier and prevent monovalent cephalexin anions penetration. Optimized nanofiltration membrane exhibits rejections of 98.9 % for 3650 ppm cephalexin, maintaining steady rejection during 69 h of continuous operations. The flux recovers to 99.3 % of the original flux after water washing. Benefiting from the separation performance of fabricated membranes, multi-stage NF processes effectively enrich the cephalexin wastewater. This work offers significant prospects for achieving high-efficiency pharmaceutical wastewater treatment and amphoteric drug recovery.

Titania and zirconia ceramic nanofiltration membrane fabrication by coating method on mullite and mullite-alumina microfiltration supports for industrial wastewater treatment

Industrial wastewater treatment increasingly relies on membrane separation, with ceramic membranes offering many advantages such as thermal stability and pH resistance. The resistance of ceramic membranes to extreme pH conditions indicates their ability to maintain structure and performance when exposed to highly acidic or alkaline environments. A high-permeability ceramic nanofiltration membrane was developed, boasting excellent rejection rates through a multilayer asymmetric design. Initially, two tubular porous supports, mullite and mullite-alumina, with a weight percent of 50, were fabricated using the extrusion method. Subsequently, a colloidal sol of titania (TiO2) and titania-zirconia (TiO2- ZrO2) was prepared via the sol–gel method and coated on the ceramic supports using the dip-coating method. After analyzing the membrane microstructure using SEM, XRD, and BET, the efficiency of the membranes in treating synthetic oily wastewater was evaluated. The results underscore the significant impact of the Donnan exclusion mechanism on the rejection of nanofiltration (NF) membranes. An increase in pressure led to a rise in rejection rates up to 7 bars. The Chemical Oxygen Demand (COD) rejection for mullite-titania zirconia (MTZ) and mullite-alumina-titania zirconia (MATZ) membranes was 98.65 % and 98 %, respectively. The pure water permeability test results for mullite and mullite-alumina supports, as well as MTZ and MATZ membranes, were recorded as 254, 382, 70, and 89 L bar-1m-2h−1, respectively.

Advancing drinking water safety: Facile fabrication of nanofiltration membrane for enhanced antibiotics removal and efficient water softening

Long-term water consumption with contaminated antibiotics and high levels of hardness threatens the health of humans and animals. In this study, a novel positively charged nanofiltration membrane was designed for the dual purpose of efficiently removing antibiotics and softening hard water. The membrane was fabricated by casting P84 polymer solution onto non-woven fabrics, followed by immersion in the polyethyleneimine (PEI) solution for phase inversion and cross-linking, and finalized interfacial polymerization with trimesoyl chloride. Notably, the rapid immersion of the P84 substrate into PEI drastically reduces preparation time by 95 % compared to the regular method while maximizing PEI storage, resulting in uniform pore sizes and a positively charged surface. The optimal membrane showed a high water permeance of 11.3 L m−2 h−1 bar−1 and exceptional antibiotic rejection, i.e., 99.6 % for enrofloxacin, 99.2 % for ciprofloxacin, and 96.3 % for sulfamethoxazole, as well as a highly effective removal in water hardness (over 96 % of Ca2+ and Mg2+) at 4 bar. Simulated water separation tests showed that the optimal membrane effectively controls hard water salinity within optimum drinking water ranges (Ca2+ ≤ 80 mg/L; Mg2+ ≤ 30 mg/L), providing efficient water softening and antibiotic capture ability. Additionally, the optimal membrane demonstrated a superior anti-bacterial and long-term stability performance. This study has significant potential for improving drinking water supply safety and addressing pressing public health and environmental concerns.

An insight into physicochemical properties of hexagonal lyotropic liquid crystal templates from amphiphiles for mesoporous structural administration

Hexagonal lyotropic liquid crystals (HLLC) provide an ideal template for the fabrication of nanofiltration membranes without the flux-selectivity trade-off problem. Amphiphiles, the core components of the columnar micelles in the HLLC system, play a key role in regulating the nanostructure, their effects on dimensional stability and physicochemical properties of the system however have not been explored well. In this research, we compared the dimensional stability and physicochemical properties of HLLC templates prepared from amphiphiles with various head groups and tail lengths. The amphiphiles with charged head groups (dodecyl trimethylammonium bromide, DTAB, and hexadecyl trimethylammonium bromide, CTAB) enable more monomers to be introduced and a much smaller (∼ 1/2) pore size than that with uncharged ones (polyethylene glycol hexadecyl ether, Brij56). The tail length however mainly regulates the width of water channels with CTAB being 23.27 Å and DTAB about 17.06 Å when the head groups are identical. Although the HLLC systems with CTAB and DTAB present a little bit higher phase transition temperature, the dynamic mechanical stability is much better than that with Brij56 at room temperature, facilitating the reorientation process under an electric force with the order parameter reaching to about 0.9 and the retention of the aligned nanostructure with the absence of the force at room temperature. The study enables a better understanding of the effects of amphiphiles on HLLC templates and their tunability for advanced nanofiltration membranes.

Application of a functionalized thin-film composite nanofiltration membrane in water desalination

To prepare a thin-film nanocomposite (TFN) nanofiltration (NF) membrane, characterized with high desalination rate and antifouling performance, carboxylated multi-walled magnetic 1,2,3,4-butanetetracarboxylic acid carbon nanotubes (hereafter, the C-MWCNT-MBTCA) with a choice of hydrophilic groups were initially synthesized in this study, and then incorporated into the polyamide (PA) layer via interfacial polymerization (IP). After that, the surface morphology and hydrophilicity of the fabricated NF membrane was examined by the field emission scanning electron microscopy (FESEM) and water contact angle measurements, respectively. To assess the membrane application, the solutions (2000 mg/L) of sodium sulfate (Na2SO4), magnesium sulfate (MgSO4), calcium chloride (CaCl2), and sodium chloride (NaCl) were consistently tested. On account of the ample carboxylic acid (R-COOH) groups in the modified TFN membrane, the study outcomes revealed that the given membrane could enhance the flux along with the desalination rate upon the addition of the C-MWCNT-MBTCA (0.04 wt%). Likewise, the pure water flux significantly grew from 58.8 to 110.5 Lm-2h−1 after the utilization of the C-MWCNT-MBTCA (0.04 wt%), and the Na2SO4 removal rate promoted from 87 to 98 %. Ultimately, it was established that the C-MWCNT-MBTCA could be used as an economical modifying agent to boost the performance of NF membranes for water desalination purposes.

Fabrication of nanofiltration membrane with enhanced water permeability and dyes removal efficiency using tetramethyl thiourea-doped reduced graphene oxide

Fabrication of nanofiltration membrane with enhanced water permeability and dyes removal efficiency using tetramethyl thiourea-doped reduced graphene oxide

Dynamic simulation of a novel liquid desiccant air-conditioning system for greenhouse cooling and water recovery

We present dynamic, hour-by-hour modelling of a multi-stage nanofiltration regeneration system for liquid desiccant air-conditioning (NF-LDAC) of horticultural greenhouses in 17 locations covering four climate types. Four technologies are compared: fan ventilation, evaporative cooling (EvapC), conventional air-conditioning (AC), and NF-LDAC. The comparison is based on acceptable conditions for cultivation and coefficient of performance (COP). On average, fan ventilation and EvapC achieve acceptable conditions for 2 months per year, compared to 5.4 and 10.5 months for AC and NF-LDAC respectively. The highest COP value of 7.6 for NF-LDAC is reached at Colombo (Sri Lanka), followed by 5.3 at Mecca (Saudi Arabia). The permeate of the multi-stage regenerator can be recycled for irrigation, providing water savings. The highest water saving of 63% is at Mecca. These results are inferior but more realistic than those from an earlier idealised and steady-state model, which predicted a COP of 12.4 and water savings of 100% at Mecca. Nevertheless, in hot desert climates, NF-LDAC maintains acceptable conditions for year-round cultivation and saves water that is scarce in such climates. Future advances in nanofiltration membrane fabrication could increase the COP of NF-LDAC to 12.1 at Colombo and 7.4 at Mecca.

Electric-field strengthening uranium extraction from seawater assisted by nanofiltration membranes with sieving-adsorption properties

Electric-field driven uranium extraction from seawater has been proved to greatly enhance the performances of various adsorbents via gathering uranyl ions at the surfaces, but high-concentration interfering cations would also be enriched which generates shielding effects to reduce adsorption capacity. To address this issue, we have fabricated nanofiltration membranes with sieving-adsorption properties by choosing polyamidoxime (PAO) as substrates and polyamide as skin layers. On the one hand, the polyamide skin layers fabricated by interfacial polymerization could effectively separate uranyl ions from other metal ions according to the size-sieving effect since the size of uranyl ions is much larger than most interfering cations. The results demonstrated that the nanofiltration membranes could nearly 100 % reject uranyl ions while the rejections of other metal ions below 30 %. On the other hand, the rejected uranyl ions would be enriched at the surfaces of PAO substrates and followed by adsorption. The increased uranium concentrations are beneficial for both adsorption capacity as well as adsorption rate. Therefore, the adsorption capacity increased by 30 % compared with the pristine PAO adsorbents. This work not only provides a new strategy for the design of high-performance adsorbents, but also could promote the engineering process of uranium extraction from seawater which has an important scientific significance and application value.

Fabrication of nanofiltration membranes through the deposition of polyethyleneimine on SMA-polyethersulfone supports under acid catalysis for cationic dye/salt separation

Organic selective nanofiltration membranes, with high organic rejections and salt passages, have attracted extensive research attention, especially for dye/salt separations. In the present work, nanofiltration membranes with lower MWCO were prepared by depositing PEI aqueous on porous supports containing poly (styrene-maleic anhydride) (SMA), under the catalysis of sulfuric acid. The amines in PEI reacted with the anhydrides in SMA through electrophilic protonation–addition, forming a crosslinked dense layer. Under the optimal conditions, a nanofiltration membrane with a permeance of about 24.3 Lm−2h−1bar−1 and a MWCO of about 400 Da was obtained. The membrane was further evaluated by filtrating aqueous solutions of dye and/or salt. The rejections of cationic dyes (crystal violet and methylene blue) were as high as 99.9%. The rejection of Na2SO4 was only 3.6%. During the 24 h filtration process of the crystal violet and Na2SO4 mixed aqueous solution, the separation performance remained stable, indicating the PEI/SMA-PES nanofiltration membrane had excellent organic-water selectivity and organics-salts selectivity. The membrane may have good potential in positively charged dye desalination.

The effect of diamine structure on the chemical stability of polyamide nanofiltration membranes: Experimental and density functional theory studies

Monomers are elementary units that constitute the polyamide layer, which determines the properties of nanofiltration membranes. The design of nanofiltration membranes with both high separation performance and outstanding chemical stability remains a challenge. In this study, two typical monomers, heterocyclic monomer molecule-piperazine (PIP) and carbon ring molecule-1,4-cyclohexane diamine (CHDA), were applied as aqueous monomers for interfacial polymerization to generate polyamide nanofiltration membranes. The physicochemical properties of the two nanofiltration membranes were comprehensively investigated. The results demonstrated that the nanofiltration membrane fabricated via CHDA exhibited more chemical stability than that fabricated via PIP. The mechanisms influencing the chemical stability difference were elucidated via multiscale simulation. The CHDA polyamide has higher levels of HOMO-LUMO energy and Gibbs-free energy, which make it more stable under harsh chemical environments. Overall, this work presents the effect of the diamine structure on the chemical stability of polyamide NF membranes, which can inspire highly chemically stable nanofiltration membrane fabrication.

Nanofiltration Membranes for the Removal of Heavy Metals from Aqueous Solutions: Preparations and Applications.

Water shortages are one of the problems caused by global industrialization, with most wastewater discharged without proper treatment, leading to contamination and limited clean water supply. Therefore, it is important to identify alternative water sources because many concerns are directed toward sustainable water treatment processes. Nanofiltration membrane technology is a membrane integrated with nanoscale particle size and is a superior technique for heavy metal removal in the treatment of polluted water. The fabrication of nanofiltration membranes involves phase inversion and interfacial polymerization. This review provides a comprehensive outline of how nanoparticles can effectively enhance the fabrication, separation potential, and efficiency of NF membranes. Nanoparticles take the form of nanofillers, nanoembedded membranes, and nanocomposites to give multiple approaches to the enhancement of the NF membrane's performance. This could significantly improve selectivity, fouling resistance, water flux, porosity, roughness, and rejection. Nanofillers can form nanoembedded membranes and thin films through various processes such as in situ polymerization, layer-by-layer assembly, blending, coating, and embedding. We discussed the operational conditions, such as pH, temperature, concentration of the feed solution, and pressure. The mitigation strategies for fouling resistance are also highlighted. Recent developments in commercial nanofiltration membranes have also been highlighted.

Elucidation on Performance and Structural Properties of Skinned Asymmetric Nanofiltration Membrane Based on Theoretical Models

In this study, the performance and structural properties of enhanced skinned asymmetric nanofiltration (NF) membranes were experimentally and theoretically analyzed. Based on Donnan and steric-hindrance transport mechanism, the relationship of performances and key properties of the fabricated nanofiltration membranes were examined. At the optimum concentration of polymer, the skinned nanofiltration membranes achieved high salt rejection up to 85% and high solutes separation efficacy. Moreover, morphological and modeling analysis discovered that, the optimum membranes produced good pore size and fine key properties with 1.20 nm of pore radius, 4.96 µm of ratio of thickness to porosity (∆x/Ak) and −1.56 of surface charge, ζ as well as uniform pore size distributions. The findings from this study proved that the strategic utilization and manipulation of good membranes material is a simple and good attempt to upgrade the membranes capability and usability which lead towards the application in various membrane separation processes.

Employing sulfolane as a green solvent in the fabrication of nanofiltration membranes with excellent dye/salt separation performances for textile wastewater treatment

This study explores the potential use of sulfolane, a green and sustainable solvent, as an alternative to toxic solvents in the fabrication of high-performance nanofiltration membranes. A comparison of Hansen solubility parameter (HSP) with N-methyl-2-pyrrolidone (NMP) indicates that sulfolane is a “poor” solvent for the sulfonated polyphenylenesulfone (sPPSU) polymer, which results in a lower critical polymer concentration (CPC) required to produce a macrovoid-free membrane structure. Moreover, the addition of a low molecular weight hyperbranched polyethyleneimine (HPEI) of MW = 800 g/mol as a crosslinker enhances the mechanical rigidity of the membranes without affecting the pore structure required for retaining salts from dye/salt mixtures, enabling practical applications in wastewater treatment. Notably, the membranes demonstrate exceptional dye/salt separation performance with a separation factor SDye/Salt of up to 69.32, even for low molecular weight dyes as low as 268 g/mol (i.e., a Disperse blue 1 and Na2SO4 mixture). To the best of our knowledge, this is the lowest MW dye ever tested for dye/salt separation. The membranes also show good antifouling capability over an extended period of use. Literature comparison shows that the sPPSU/sulfolane membrane crosslinked with HPEI800 for 60 min, referred to as sPSlf-c60, exhibits superior dye/salt separation performance, indicating their potential for the treatment of textile wastewater effluents.

Interfacial Polymerization on Polyethersulfone Ultrafiltration Membrane to Prepare Nanofiltration Layers for Dye Separation.

Nanofiltration membranes are of great significance to the treatment of dye wastewater. Interfacial polymerization is a widely used method to fabricate nanofiltration membranes. In this study, the interaction of tannic acid-assisted polyethylene polyamine (PEPA) with terephthalaldehyde (TPAL) was performed on PES ultrafiltration membranes using novel nitrogen-rich amine monomers and relatively less reactive aldehyde-based monomers. A new nanofiltration membrane ((T-P-T)/PES) was prepared by interfacial polymerization. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy were used to analyze the elemental composition, bonding state, and surface morphology of the membrane surface. The effects of the PEPA deposition time, TPAL concentration, interfacial reaction time, and curing time on the nanofiltration layer were investigated. The modified membrane, prepared under optimal conditions, showed strong dye separation ability. The permeation of the modified membrane could reach 68.68 L·m-2·h-1·bar-1, and the rejection of various dyes was above 99%. In addition, the (T-P-T)/PES membrane showed good stability during long-term dye separation.

Simultaneous regulation of pore size and surface charge of nanofiltration membrane using carbon quantum dots for improved selective separation

Designing nanofiltration (NF) membranes with tunable pore sizes and surface charges is highly desirable to meet the growing demand for precise separation. In this study, carbon quantum dots generated through lysine pyrolysis (l-CQDs) were utilized as monomers to fabricate NF membranes via interfacial polymerization (IP). Intriguingly, the surface charge (from negative to positive) and effective pore size (from loose to dense structure) of the resultant NF membranes could be simultaneously modulated by simply adjusting the diffusion of l-CQDs during the IP process, which endowed the obtained l-CQD-based NF membrane with a tunable separation performance. The negative and loose NF membranes (l-CQD; 0.1 wt%) achieved excellent dye/salt fractionation performance even at high NaCl concentrations (20 g/L). The recovered NaCl from the highly saline dyeing effluent could be directly reused in cotton fabric dyeing, indicating potential application prospects in the treatment of saline textile effluents. A dense and positive NF membrane was obtained when l-CQD concentration increased to 1.0 wt%; this membrane showed exceptional desalination performance with high rejection of MgCl2, CuCl2, and CaCl2 (98.77 %, 99.06 %, and 99.0 %, respectively), demonstrating the ability to remove metal ions from water. This work provides an approach for preparing NF membranes with tailorable pore size and surface charge and highlights the potential of l-CQD-based NF membranes for the practical separation toward various charged components.

Pilot scale nanofiltration membrane fabrication containing ionic co-monomers and halloysite nanotubes for textile dye filtration.

Wastewater from the textile industry contains high concentrations of pollutants, so the wastewater must be treated before it is discharged. In addition, the reuse of treated wastewater should be considered from an environmental point of view, as large volumes of wastewater are produced. Since textile wastewater mainly contains dyestuffs, it must be treated effectively using environmentally friendly technologies. Membrane processes are widely used in textile wastewater treatment as they have distinct advantages over conventional wastewater treatment methods. This study reports the pilot-scale manufacturing and characterization of three different NF membranes. Three different types of membranes were fabricated. The fabricated membranes were compared through characterization by surface properties, chemical structure and morphology. Membranes were tested for pure water flux. Then the synthetic wastewater (SWW) was tested for flux and rejection. Lastly, the textile wastewater was tested. The textile wastewater flux of pure piperazine (PIP), 60% S-DADPS and 0.04% halloysite nanotubes (HNTs) were 22.42, 79.58 and 40.06 L m-2 h-1. It has been proven that the 60% s-DADPS membrane provides up to four times improvement in wastewater flux and simultaneously. In addition, NF membranes produced using HNT and sDADPS on a pilot scale have brought innovation to the literature with the good results obtained.

Nanofiltration membrane with CM-β-CD tailored polyamide layer for high concentration cephalexin solution separation

Nanofiltration (NF) is a promising technique to achieve sustainable and efficient separation of antibiotics with high industrial value. In this work, carboxymethyl-β-cyclodextrin (CM-β-CD) modified nanofiltration membrane was fabricated through interfacial polymerization (IP) for high concentration cephalexin solution separation, which is a classic antibiotic pharmaceutical wastewater. In principle, CM-β-CD can slow down the diffusion of amine monomers via electrostatic attraction, steric effect, hydrogen bonding and adsorption of the piperazine (PIP) monomer onto the hydrophilic surface, which renders amine monomer the high local concentration. The fabricated NF membranes possessed a larger proportion of dense primary layer on the surface. In addition, the accumulation of CM-β-CD between the substrate membrane and polyamide (PA) layer played the role as a barrier with specific cavity structure and bulk carboxylate to enhance the rejection of cephalexin. The cavity structure and stacking gap of CM-β-CD simultaneously rendered the membrane interlayer highly permeable. The optimal CM-β-CD modified membrane exhibited high rejection of cephalexin (94.7%) and water permeability of 122.4 L m−2 h−1 MPa−1 when the concentration of cephalexin was 3473.9 ppm (10 mmol/L). This work furnished an available way to prepare a novel nanofiltration membrane with efficient separation performance for relevant pharmaceutical production wastewater.

Ultrafast loose nanofiltration membrane intercalated by in-situ grown nanoparticles for dye purification and reuse

Loose nanofiltration membrane is regarded as an effective separation technology for dye purification and reuse, but is still restrained by the trade-off between the permeance and the dye/salts selectivity. Herein, we report the fabrication of an ultrafast loose polyamide nanofiltration (NF) membrane on the nanofibrous support layer with uniform in-situ grown ZnO nanoparticles. It was found that embedding ZnO nanoparticles provides more water channels and increased effective filtration area, thus enhancing the water permeation without trading off the dye/salt selectivity. The fabricated NF membrane with an in-situ formed ZnO-nanoparticle interlayer exhibits an ultrahigh water permeance up to 375 L m−2 h−1 bar−1, which increased by approximate seven-fold than that of virgin NF membrane (54 L m−2 h−1 bar−1) without nanoparticles intercalated, and attains high rejection of organic dyes (>91 % for Congo red, >92 % for Methyl blue, and >98 % for Victoria blue B) but low rejection of inorganic salts (<5 %). The synergy of steric exclusion and charge effect dominate the high selectivity of dye and salts. This study unlocks a new avenue to synthesize ultrahighly permeable-selective loose NF membranes.

Optimization of amine functionalization of MCM-41 for its covalent decoration in nanofiltration membranes for purification of saline- and micropollutant-contaminated feeds

This work presents the novel triamine-functionalized MCM-41 material and its utilization for the fabrication of nanofiltration membranes via crosslinking to the polyamide active layer for desalination and micropollutant removal.

Rapid co-deposition of dopamine and polyethyleneimine triggered by CuSO4/H2O2 oxidation to fabricate nanofiltration membranes with high selectivity and antifouling ability

Membrane surface properties play important roles in the separation performance and fouling behavior during the membrane-based water treatment processes. Mussel-inspired polydopamine (PDA) layer with abundant functional groups can endow the membrane surface with increased hydrophilicity as well as extraordinary versatility and creative potential for further functionalization toward specific applications. However, the slow deposition rate still limits its application in membrane modification. In this study, rapid deposition of the PDA layer on the surface of the polysulfone membrane was realized by catalytic oxidation using CuSO4/H2O2. Meanwhile, polyethyleneimine (PEI) was introduced to co-deposit with PDA to obtain a hydrophilic, uniform, and electroneutral separation layer for the nanofiltration membrane. An optimized stoichiometry of modifiers and oxidants was obtained by UV–vis absorbance measurement. The membrane surface properties including surface morphology, roughness, chemical element compositions, wettability, and charge behavior before and after modification were characterized through various techniques. The optimized PDA/PEI modified membrane (a-Cu(15)-PDA/PEI) possessed higher MgCl2/NaCl and dye/salt selectivities as well as improved anti-fouling performance compared to the commercial NF-270 membrane. Furthermore, the Gaussian simulation combined with XPS analysis illustrated that the introduction of Cu2+/H2O2 accelerated the dopamine oxidation and facilitated the formation of CO quinoid structures, thus providing more reactive sites for the Schiff base reaction in the PDA/PEI co-deposition process. The results from this study provide theoretical foundations for improving nanofiltration membrane performances by PDA/PEI modification.