NF Membranes Research Articles

Polyamide nanofiltration membrane fabricated with ultra-low concentration triaminoguanidine showing efficient desalination performance

Tuning the reactivity and diffusion of amine monomers in interfacial polymerization (IP) process could efficiently regulate the formation and structure of the polyamide (PA) selective layer. Herein, novel thin-film composite NF membranes with dense and ultrathin PA selective layer were fabricated using 1,3,5-benzenetricarbonyl trichloride (TMC) and ultra-low concentration triaminoguanidine (Tg) as reactive monomers. Fabrication parameters, including Tg concentration, NaOH concentration and reaction time, were systematically explored to optimize the desalination performance of PA-Tg NF membrane. During the stability test over 48 h, PA-Tg-0.06 membrane displayed a water permeance of ∼12 L m−2 h−1·bar−1 and Na2SO4 rejection of ∼99%. Meanwhile, detailed comparisons were made between PA-Tg NF membrane and a typical NF membrane fabricated with PIP as an aqueous monomer, including characteristics of the monomers as well as the structure, water permeance, salt rejection and antifouling property of the membranes. Molecular dynamics simulation and interfacial diffusion experiments indicated that the Tg monomer exhibited a higher reactivity but a lower diffusivity than the PIP monomer, making it feasible for the fabrication of PA-Tg NF membrane with ultra-low concentration of Tg monomer. In addition, compared with the PA-PIP membrane, the PA-Tg membrane exhibited a smoother, more hydrophilic and negatively charged surface, as well as a thinner and denser selective layer, thereby showing a higher water permeance, salt rejection and stronger fouling resistance.

Tailoring the selectivity of quasi-PIMs nanofiltration membrane via molecular flexibility of acyl chloride monomers for desalination from dye effluents

Nanofiltration is a promising technology to recover dye from textile wastewater with highly saline for sustainable resource recovery. However, it is difficult for the conventional piperazine-based nanofiltration membranes, which usually have a tight polyamide matrix structure, to precisely separate dye and salt in wastewater. In this study, 5,5,6’,6’-tetrahydroxy-3,3,3’,3’-tetramethyl spirobisindane (TTSBI) with rigidly contorted structure has been used instead of piperazine as aqueous-phase monomer to fabricate polyarylate (PAT) nanofiltration membranes with quasi-PIMs structure via interfacial polymerization (IP) with three types of acyl chloride, i.e., rigid trimesoyl chloride (TMC), short-chain glutaryl chloride (GC) and long-chain sebacoyl dichloride (SDC). The contorted structure of TTSBI introduces extra microporosity in nanofiltration membranes, and the differentia of three acyl chlorides in molecular flexibility further endows with tailoring the stacking density of as-formed PAT networks. The PAT NF membranes thereby exhibited high permeability and tunable size-selectivity in desalination from dye effluent. Among these PAT membranes, TTSBI-TMC membranes had the highest water flux of 480.5 LMH, nearly 7-fold increase compared traditional PA NF membranes, whereas TTSBI-SDC membranes had the highest dye rejection of 97.4%, and TTSBI-GC membrane had the relatively balanced dye desalination performance with high rejection 95.4% for Congo Red and 8.3% for NaCl accompanied by high flux of 402.4 LMH. Therefore, this study provides a new prospective for the fabrication of highly permeable nanofiltration membranes for precise separation.

Polyethylenimine-mica nanosheets/cellulose nanofibers stacked loose nanofiltration membrane for effective dye/salt separation

Dye recovery and desalination efficiency in textile wastewater treatment are of great significance, but the traditional treatment technologies cannot meet these two requirements simultaneously. In this study, a novel loose NF membrane was prepared by the assembly of PEI-modified mica (PEI-mica) and cellulose nanofibers (CNFs) on hydrolyzed polyacrylonitrile (HPAN) substrate via facile vacuum filtration. The combination of PEI-mica nanosheets and CNFs constructed a thin and loose “brick-mud” structure via electrostatic attraction and hydrogen bonding. The 2D nanochannels among the stacked PEI-mica nanosheets well-tailored by CNFs allowed the transport of water molecules and salt ions while resisting dye molecules. Due to the well-designed lamellar structure along with the excellent hydrophilicity, the PEI-mica/CNFs membrane possessed high water permeability (62.18 LMH/bar) and superior dye/salt separation efficiency, with outstanding dye retentions (i.e., Coomassie Brilliant Blue R250: 99.66 %, Congo Red: 98.89 %, and Evans Blue: 98.64 %) and low salt rejections (e.g., NaCl: 3.42 % and Na2SO4: 15.63 %). Besides, the composite membrane also showed good antifouling properties and operation stability, indicating its promising potential for practical textile wastewater treatment.

Effect of activated carbon nanoparticles on the performance of PES nanofiltration membranes to separate kraft lignin from black liquor

In this work, activated carbon nanoparticles (AC) at concentrations ranging from 0 to 1 wt% were used to prepare polyethersulfone nanofiltration membranes. The effectiveness of these membranes in separating lignin from black liquor (BL) was evaluated under various operating conditions. The addition of AC improved all desirable properties. For instance, water permeability was increased by 57.50 % with the addition of 1 % AC and surface hydrophilicity was improved by reducing the contact angle from 66.8° to 55.2° for 0.5 % AC-based membranes compared to simple polymeric membranes. For BL filtration, 0.1 % AC-based membranes offered the highest flux with an improvement of 120 % at 24 bar and high lignin rejection compared to simple polymeric membranes. In addition, these membranes exhibited the highest water permeability recovery of 98.02 % when used for BL filtration followed by cleaning. During optimization tests of the main operating variables (temperature, pressure and pH) using 0.1 % AC-based membranes, it was found that extremely high conditions for each variable resulted in decreased performance in terms of fouling and lignin rejection. The best performance of these membranes in terms of flux, lignin rejection and fouling resistance was observed around 40 °C, 20 bar and 11.5 pH within the studied range. In this study, a new application for AC-based NF membranes was established for the separation of lignin from BL. The results of this study also showed that under optimal conditions, the performance of AC-based (0.1 %) membranes was improved for the efficient separation of lignin from BL with lower membrane fouling.

Combining Ultrafiltration and Nanofiltration to Obtain a Concentrated Extract of Purified Polyphenols from Wet Olive Pomace

Despite the environmental concerns raised every year by the generation of high volumes of wet olive pomace, it contains valuable phenolic compounds that are essential for the valorization of this by-product. In this work, an integrated process to recover phenolic compounds from wet olive pomace is proposed. It consists of ultrasound-assisted solid-liquid extraction, followed by ultrafiltration and nanofiltration. Several commercial membranes were studied at different operational conditions. The ultrafiltration stage allowed the purification of biophenols, which were obtained in the permeate stream. Regarding organic matter, satisfactory rejection values were obtained with both commercial UH030 and UP005 membranes (Microdyn Nadir), but the latter provided more efficient purification and higher values of permeate flux, above 18 L·h-1·m-2 at 2.5 bar and 1.5 m·s-1. Later, this permeate stream was concentrated by means of a nanofiltration process, obtaining polyphenol rejection values that surpassed 85% with the commercial NF270 membrane (DuPont), then achieving the concentration of the previously purified polyphenols.

Chemical-free production of multiple high-value bioproducts from metabolically engineered transgenic sugarcane ‘oilcane’ bagasse and their recovery using nanofiltration

Bioenergy crops have potential for being a sustainable and renewable feedstock for biofuels and various value-added bioproducts. The study utilizes recently developed transgenic sugarcane (‘oilcane’) bagasse for chemical-free coproduction of high-value bioproducts, i.e., furfurals, HMF, acetic acid, cellulosic sugars, and vegetative lipids. Hydrothermal pretreatment was optimized at 210 °C for 5 min to coproduce 6.91%, 2.67%, 5.07%, 2.42% and 37.82% (w/w) furfurals, HMF, acetic acid, vegetative lipids, and cellulosic sugars, respectively from lignocellulosic biomass. Additionally, nanofiltration system in-series was successfully established to recover sugars, furfurals, HMF, and acetic acid from the pretreatment liquor. 1st nanofiltration with Duracid NF membrane rejected ∼99% sugars. Concentrated sugars with significantly reduced inhibitory products were obtained in retentate for fermentation. 2nd nanofiltration with NF90 membrane used permeate of 1st nanofiltration as feed and rejected ∼ 86% furfurals. The work demonstrates the feasibility of coproducing and recovering multiple biochemicals from lignocellulosic biomass.

Fabrication of hollow fiber nanofiltration membrane with high permselectivity based on “Co-deposition, biomineralization and dual cross-linking” process

In this work, the organic-inorganic hybrid separation layer containing BaSO4 or CaC2O4 was fabricated on the membrane outer surface through the combination of polyvinylamine (PVAM)-tannic acid (TA)-metal ion co-deposition, dual cross-linking and biomineralization. Based on the synergistic coordination effect between TA and PVAM, metal ions were anchored within the separation layer. The strong interaction ability between functional groups of organics and metal ions enhanced the attaching stability of mineralized substances. Characterizing the chemical composition, hydrophilicity, microstructure, and potential of the NF membrane's outer surface allowed for a thorough investigation and comparison of the impact of mineralized substances on the separation performance of NF membrane. The results indicated that the introduction of mineralized substances provided the permeance path for water molecule and reduced the water transmission resistance, which not only increased the permeability (53.4 L m−2 h−1 bar−1) by 2.7 times, but also remained ultrahigh removal capacity for both Mg2+ and Ca2+ (>99%). Furthermore, the NF membrane also exhibited satisfactory acid resistance, anti-fouling capacity and favorable operation stability. This work demonstrated excellent potential in wastewater recovery and rapid desalination, serving as a reference for the development of high-performance NF membrane with positively charged surface.

A novel positively charged nanofiltration membrane stimulated by amino-functionalized MXene Ti3C2Tx for high rejection of water hardness ions

The demand to address issues such as drinking water safety and industrial fouling caused by high-hardness ions has still emphasized the development of advanced membrane materials. In this study, through a maneuverable amide-cross-linking strategy, a new positively-charged polyamide (PA) nanofiltration membrane was developed for the first time by incorporating amino-functionalized Ti3C2Tx nanoparticles (Ti3C2Tx-NH2, TN). In addition to the induced electropositivity, the hydrophilicity of the as-obtained PA-TN membrane was also elevated with a maintained nodular structure by tailoring the interfacial polymerization reaction process of piperazine (PIP) with trimesoyl chloride (TMC). Therefore, the newly developed PA-TN membrane exhibited both superhigh rejection of Ca2+ and Mg2+ over 96%, and the flux increased 2–3 times even for the salinity solutions than many similar NF membranes reported in literature. Furthermore, the enhanced long-term stability and fouling resistance of the PA-TN membrane was also validated due to its new organic-inorganic structural coupling and improved hydrophilicity. This work provides a new strategy for the preparation of organic-inorganic hybrid positively charged nanofiltration membranes for water softening treatment.

Effect of pressure and cross-flow velocity on membrane behaviour in red wine nanofiltration

Nanofiltration has found numerous applications in winemaking industry as an effective separation technology, allowing for the recovery and concentration of valuable bioactive compounds from wine/grape by-products, as well as for wine dealcoholization. However, the assessment of membrane fouling remains essential for a stable and sustainable membrane operation. Because of its complex nature, wine components (colloids and solutes such as polysaccharides, polyphenols, proteins) contribute to different mechanisms of fouling. The increase of fouling propensity as well as the conditions that contribute to it - transmembrane pressure and cross-flow velocity – are studied in the present study. Quantitative characteristics as fouling indices are discussed. Results with red wine (Mavrud) nanofiltration are obtained using two NF membranes - Nadir® NP030 P (asymmetric polyethersulfone (PES), MWCO 500 Da) and Alfa Laval NF99HF (thin film composite polyester, MWCO 200 Da). Nanofiltration runs were carried out by a constant-pressure cross-flow filtration system MaxiMem, Prozesstechnik GmbH with a rectangular flat-sheet membrane of 215 cm2 active area.Effect of transmembrane pressure (TMP) (10 to 50 bar) and cross-flow rate (1-3 l/min) on the permeate flux are discussed in view of membrane fouling. Higher operating pressures enhance the permeate flux but may also lead to increased fouling. The two membranes show very different permeate fluxes, the ones measured with NF99HF being 10-20 times higher. Increase in cross-flow velocity improves the hydrodynamic conditions such as shear stress field close to the membrane. The expected positive effect on permeate flux is the more noticeable the more pronounced the fouling. This was shown by two polymer membranes of different molecular weight cut-off exhibiting different susceptibility to fouling.

A Review: End Of Life Reverse Osmosis Membrane Conversion And Its Prospects In The Study Of Conversion To Reconditioned Membrane

Reverse Osmosis (RO) is the most widely applied water purification technology worldwide. However, RO membranes have a short service life before they become waste (End of Life RO/EoL RO), so they must be incinerated or disposed of in landfills. Several sustainability solutions have been proposed and studied in recent years. Therefore, a comprehensive review of the emerging trends in the reuse of EoL RO membranes is presented in this paper. Recycling EoL RO membranes is the most preferred option to solve this waste problem either as direct reuse or after conversion into other types of membranes. Direct reuse of EoL RO membranes can be divided into three categories, such as rejuvenation of EoL RO membranes, use at lower rates of treatment, and use for new applications. Rejuvenation of EoL RO can be done by cleaning treatment, use at a lower level can be done by converting it into NF, UF or MF membranes and EoL RO can be made into recycled products by utilizing parts of the EoL RO membrane module. A review of prospects and challenges faced in the conversion process into reconditioned membranes is also presented in this paper.

New technology for preparing energetic materials by nanofiltration membrane (NF): rapid and efficient preparation of high-purity ammonium dinitramide (ADN).

The development of environment-friendly and non-toxic green energetic materials and their safe, environmentally friendly, and economical production is very important to the national economy and national security. As an innovative, efficient, and environmentally friendly energetic material, the preferred preparation method of ammonium dinitramide (ADN) is the nitro-sulfur mixed acid method, which has the advantages of high yield, simple method, and easy access to raw materials. However, the large number of inorganic salt ions introduced by this method limits the large-scale production of ADN. Nanofiltration (NF) has been widely used in various industrial processes as a separation method with high separation efficiency and simple operation. In this study, NF was used for the desalination and purification of ADN synthesized by the mixed acid method. The effects of NF types, operation process (pressure, temperature, and feed solution concentration) on desalination efficiency, and membrane flux during purification were examined. The results showed that 600D NF could achieve the efficient desalination and purification of ADN. It was verified that the highest desalination and purification efficiency was achieved at 2 MPa pressure, 25 °C, and 1 time dilution of the feed solution, and the membrane flux of the desalination and purification process was stable. Under the optimized process conditions, the removal rate of inorganic salts and other impurities reached 99% (which can be recycled), the purity of ADN reached 99.8%, and the recovery rate reached 99%. This process has the potential for the large-scale production of ADN and provides a new process for the safe, efficient, and cheap preparation of energetic materials.

Recent Advanced Development of Acid-Resistant Thin-Film Composite Nanofiltration Membrane Preparation and Separation Performance in Acidic Environments

Membrane filtration technology has attracted extensive attention in academia and industry due to its advantages of eco-friendliness related to environmental protection and high efficiency. Polyamide thin-film composite nanofiltration (PA TFC NF) membranes have been widely used due to their high separation performance. Non-acid-resistant PA TFC NF membranes face tremendous challenges in an acidic environment. Novel and relatively acid-resistant polysulfonamide-based and triazine-based TFC NF membranes have been developed, but these have a serious trade-off in terms of permeability and selectivity. Hence, how to improve acid resistance of TFC NF membranes and their separation performance in acidic environments is a pivotal issue for the design and preparation of these membranes. This review first highlights current strategies for improving the acid resistance of PA TFC NF membranes by regulating the composition and structure of the separation layer of the membrane performed by manipulating and optimizing the construction method and then summarizes the separation performances of these acid-resistant TFC NF membranes in acidic environments, as studied in recent years.

Interaction between surfactants of different classes and nanofiltration membranes

The presence of surfactants in aquatic environments may alter the water quality parameters. Nanofiltration is a promising technique that can separate surfactants from water with high rejections. Nevertheless, negative charges on nanofiltration membranes could facilitate the occurrence of electrostatic interactions between the charged surfactants and the surface of these membranes, increasing the membrane-fouling tendency. In this work, the interaction of surfactants commonly found in residential laundry wastewater with membranes used in nanofiltration was investigated. For this purpose, the surface, and transport properties of four commercial membranes were analyzed. The zeta potential of the NF90 membrane in the presence of individual and mixture of surfactants was performed to evaluate the effect of adsorption of these surfactants on the performance of the membrane. Additionally, a central composite rotatable design (CCDR) and response surface model were applied to investigate the simultaneous effect of the initial concentration of CTAB and SDS ([CTAB + SDS]0) and pH on the NF90 permeate fluxes and rejections. It was shown that surfactant adsorption varies with the type of surfactant and membrane. Moreover, adsorption played an important role in NF90 membrane fouling, mainly for the cationic surfactant in individual solutions and in the mixture of surfactants. Besides adsorption, pore blocking may have affected the performance of nanofiltration for higher concentrations of surfactants. Finally, by the application of the central composite rotatable design (CCDR), it was possible to find the best conditions of pH and initial concentration of surfactants for achieving higher fluxes and rejections by the NF90 membrane.

Evaluation of Commercial Reverse Osmosis and Nanofiltration Membranes for the Removal of Heavy Metals from Surface Water in the Democratic Republic of Congo

This study evaluates the performance of commercial reverse osmosis (RO) and nanofiltration (NF) membranes for the removal of metal ions from synthetic water and surface water carried from the north-west of Lake Tanganyika in the city of Uvira, in the east of the Democratic Republic of Congo. Metal ion analyses were performed by the standardized ICP-MS and ICP-OES methods. The RO membrane showed higher metal ion rejection in high-concentration solutions (synthetic samples) prepared in the laboratory as well as in low-concentration samples from real raw water collected near Lake Tanganyika. Rejection levels were higher than 98% for Cr3+, Pb2+, Cd2+, As3+, Ni2+, and Sb+3 ions in the synthetic solutions, and 99.2, 98.8, 98.6, 99.2, 98.4, and 98.8%, respectively, in the real samples. The concentrations of metals in the permeate varied depending on the feed concentration and were 0.15 to 1.02 mg/L, 0.33 to 22 mg/L, and 0.11 to 22 mg/L in RO, NF90, and NF270 membranes, respectively. Regarding the NF membranes, the rejection of Cr, Ni, and Cd ions was interesting: 98.2, 97.8, and 92.3%, respectively. However, it was lower for Pb, As, and Sb ions: 76.9, 52.5 and 64.1%, respectively. The flux of NF was 329 to 375 L/m2.h, much higher than for RO membranes, which had a flux of 98 to 132 L/m2.h. The studied membranes are thus a feasible solution to remove the studied metals from real water sources at low concentrations since they meet the standards of the World Health Organization on specific values assigned to chemicals from industrial sources and human habitation areas where these ions are present in drinking water.

Pressure-driven membrane nutrient preconcentration for down-stream electrochemical struvite recovery

Nutrient recovery from wastewater is a sustainable solution to combat the harmful release of nutrients to the environment. Here, we investigate nutrient recovery from wastewater by pre-concentration of wastewater nutrients using pressure-driven membranes prior to downstream electrochemical nutrient precipitation. When using electrochemical struvite precipitation, a higher nutrient concentration leads to a higher precipitation efficiency. Therefore, we investigate the performance of commercial nanofiltration (NF) and reverse osmosis (RO) membranes with different polymer chemistry and molecular weight cut-offs (MWCO) and discuss the membrane selection based on design goals and wastewater compositions for maximum nutrient recovery efficiency. Our results indicated that the Alfa membrane, a polyamide thin film composite (PA-TFC) NF membrane with 300 Da MWCO has the highest concentration factor in phosphorus (P) preconcentration among all the membranes studied due to the high flux and removal efficiency. BW30LE (PA-TFC, 100 Da), Synder (PA-TFC, 100–250 Da) and NF90 (PA-TFC, 200–400 Da) achieved a high concentration factor for nitrogen (N) recovery. NF90 and Synder NF membranes are able to achieve a nitrogen concentration factor similar to BW30LE RO membrane at much lower energy consumption. A multistage membrane system design is suggested using the selected membranes for effective nutrient recovery. Life cycle assessment (LCA) was conducted to characterize the environmental impact of the multistage membrane nutrient recovery system. Among the different process configurations of the selected membranes, key trends included: 1) environmental impacts across most categories increased as the number of membranes increased, and 2) as the amount of fertilizer substitute that could be produced in a given configuration increased, total environmental impacts decreased with some exceptions.

The Application of the Nanofiltration Membrane NF270 for Separation of Fermentation Broths.

The potential for nanofiltration (NF) in removing both relatively low molecular weight (MW) organic species and charged solutes from complex media is noteworthy. The main aim of the current work was to improve understanding of the separation mechanisms of fermentation broths components in the NF process. For this purpose, the experimental investigations were performed using the commercial polyamide NF270 membrane. The feed solution was ultrafiltered 1,3-propanediol (1,3-PD) broths. The separation results were analyzed and discussed in light of the detailed characteristics of both the membrane and the broth components. It has been noted that the membrane ensured the complete 1,3-PD permeability and significant rejection of some feed components. A thorough analysis showed that the retention of carboxylic acids was based on both the Donnan effect and sieve mechanism, according to the following order: succinic acid > lactic acid > acetic acid > formic acid. Indeed, acids retention increased with increasing charged acids ions valency, Stokes radius (rS) as well as MW, and decreasing diffusion coefficient (D). In turn, for ions, the following orders retention was determined: SO42− = PO43− > Cl− and Ca2+ > Na+ > NH4+ ~ K+. It indicated that the ions retention increased with increasing ions charge density, hydrated radius (rH), and hydration energy (Eh). It showed that the separation of the ions was based on the Donnan exclusion, sieving effect, and dielectric exclusion.

Scalant Removal at Acidic pH for Maximum Ammonium Recovery.

One option for new nitrogen sources is industrial liquid side streams containing ammonium nitrogen (NH4-N). Unfortunately, NH4-N often exists in low concentrations in large water volumes. In order to achieve a highly concentrated NH4-Nsolution, scalant removal is needed. In this study, scalant removal by precipitation was investigated. At alkali pH, sodium carbonate (Na2CO3) was used as a precipitation chemical while at acidic pH, the chemical used was oxalic acid (C2H2O4). At alkali pH, high Na2CO3 dose was needed to achieve low content of calcium, which, with sulphate, formed the main scalant in the studied mine water. NH4-N at alkali pH was in the form of gaseous ammonia but it stayed well in the solution during pre-treatment for nanofiltration (NF) and reverse osmosis (RO). However, it was not rejected sufficiently, even via LG SW seawater RO membrane. At acidic pH with CaC2O4 precipitation, NF90 was able to be used for NH4-N concentration up to the volume reduction factor of 25. Then, NH4-N concentration increased from 0.17 g/L to 3 g/L. NF270 produced the best fluxes for acid pre-treated mine water, but NH4-N rejection was not adequate. NF90 membrane with mine water pre-treated using acid was successfully verified on a larger scale using the NF90-2540 spiral wound element.

Ionic resource recovery for carbon neutral papermaking wastewater reclamation by a chemical self-sufficiency zero liquid discharge system

Papermaking industry discharges large quantities of wastewater and waste gas, whose treatment is limited by extra chemicals requirements, insufficient resource recovery and high energy consumption. Herein, a chemical self-sufficiency zero liquid discharge (ZLD) system, which integrates nanofiltration, bipolar membrane electrodialysis and membrane contactor (NF-BMED-MC), is designed for the resource recovery from wastewater and waste gas. The key features of this system include: 1) recovery of NaCl from pretreated papermaking wastewater by NF, 2) HCl/NaOH generation and fresh water recovery by BMED, and 3) CO2 capture and NaOH/Na2CO3 generation by MC. This integrated system shows great synergy. By precipitating hardness ions in papermaking wastewater and NF concentrate with NaOH/Na2CO3, the inorganic scaling on NF membrane is mitigated. Moreover, the NF-BMED-MC system with high stability can simultaneously achieve efficient CO2 removal and sustainable recovery of fresh water and high-purity resources (NaCl, Na2SO4, NaOH and HCl) from wastewater and waste gas without introducing any extra chemicals. The environmental evaluation indicates the carbon-neutral papermaking wastewater reclamation can be achieved through the application of NF-BMED-MC system. This study establishes the promising of NF-BMED-MC as a sustainable alternative to current membrane methods for ZLD of papermaking industry discharges treatment.

A review on membrane technology application for vegetable oil purification processes

AbstractIn current paper, a comprehensive review to contribute the present insight an implementations and the recent improvements through the diverse endeavor made by the researchers utilizing a membrane technique for degumming, deacidifying, dewaxing and discoloration edible vegetable oils with and without solvent availability and also the solvent recovery has been evaluated. Endeavors made with NF, UF, MF and non-porous membranes, have shown the capability of these membranes to predicate vegetable oil treatment. A membrane technique is noticeably simple and potentially provides many usefulness in vegetable oil purification. It appears that oils treatment with membranes, which carried out at low temperatures that provides saving energy, with real cancellation of stages, provides a promising alternate to conventional procedure, towards the accomplishment of eco-friendly and cost-effective operations that are technically sophisticated. Generally, the solvent (hexane-dilution) technique enhances the membrane oil flux. For dewaxing undiluted vegetable oils, the effective membrane was MF, whereas in dewaxing solvent-diluted oils process UF membranes were more energetic.

Architecting dual coordination interactions in polyimide for constructing structurally controllable high-performance nanofiltration membranes

Polyimide-based nanofiltration membranes (NF) featuring customizable chemical structure and outstanding comprehensive performance have garnered tremendous interest for potential applications in ions rejection. Coordinated interactions can build supramolecular networks in polyimide that reshuffle phase separation behavior during membrane formation, thus conferring microstructural flexibility to nanofiltration membranes. In this paper, novel nanofiltration membranes were prepared by constructing dual coordination interactionsin polyimide, and the structures were confirmed by NMR, FTIR, EDX, and XPS analyses. As expected, the skin and supporting layers of the PI-based NF membranes can be controlled by designing coordination conditions during membrane formation. A promising result is that the resulted NF membranes occur higher reject of metal ions than the pristine membranes prepared by conventional non-solvent induced phase separation methods. The optimized performance showed significantly higher permeability for removing Mg2+ions, giving water permeance of 477.7 L m−2 h−1·bar−1and a rejection of over 80%. Moreover, the resulted PI-based NF membranes occur better solvent resistance than the pristine NF membranes due to the enhanced coordination structures. As a preliminary study, this work gives a new strategy to regulate the microstructure of nanofiltration membranes, promising further potential for applications in ion removal.