Charged Mosaic Membrane Research Articles

Preparation of PVA-based charged mosaic membrane using screen-printed method and evaluation of ion transport properties

In this study, a polyvinyl alcohol (PVA)-based charged mosaic membrane (CMM) with a stripe-shaped charged structure from PVA-modified block copolymers was fabricated on a non-fabric support using a screen-printed method. The membrane structure of the stained CMM indicated that the striped negatively (N)- and positively (P)-charged layers with 20 μ m thickness were formed on the support. The domain sizes of the N and P layers were 173 and 203 μ m, respectively. Membrane potential measurements revealed that the charge density in the N layers of the fabricated CMM (CM-1) was almost the same as that in the P layers. A diffusion dialysis test indicated that the CM-1 had an electrolyte permselectivity of 986 between 0.1 M KCl and 0.1 M sucrose; a value which is approximately 20 times higher than that of Desalton® which is the only commercially available CMM. A water permeation test showed that CM-1 exhibited negative osmosis, which is a unique behavior of CMMs with high electrolyte permselectivity. Absolute flux in the negative osmosis was maximum when the electrolyte concentration was 0.1 M. A piezo dialysis test at an initial concentration of 500 ppm NaCl and applied pressure of 0.7 MPa, indicated that the rejection of CM-1 yielded negative value, confirming that the membrane can desalt salty water via piezo dialysis.

Charge-patterned nanofiltration membranes with polystyrene sulfonate particles and polyethyleneimine in cross-linked polyvinyl alcohol

Removing salinity has always been a challenge for wastewater treatment. Utilizing nanofiltration (NF) membranes is a promising approach. However, currently available NF membranes are less effective in monovalent salt removal. In this study, work toward the initial aim of fabricating charge mosaic membranes led to charge-patterned NF-selective films on polyether sulfone (PES) or polyacrylonitrile (PAN) support membranes, with similar rejection for mono- and divalent salts. The membranes were fabricated by a two-step layer assembly of first negatively charged polystyrene sulfonate (PSS) particles immobilized in a polyvinyl alcohol (PVA) layer, followed by coating a positively charged polyethyleneimine (PEI) layer. Both PVA and PEI were crosslinked using glutaraldehyde that had initially been impregnated into the support membrane. The type of support membrane, nanoparticle, PVA, and PEI concentrations during fabrication, as well as feed pH and salt concentration, play significant roles in separation performance of obtained composite membranes. Charge-patterned NF membranes fabricated using 0.5 wt.% PVA and 0.05 wt.% PSS for assembly of the first layer followed by coating 0.5 wt.% PEI solution had even somewhat higher rejection for monovalent salt (NaCl; ∼82%) compared to multivalent salts (Na2SO4, MgSO4, and MgCl2; ∼74%), at a permeance of 5.5 LMH/bar on the PES and 3.1 LMH/bar on the PAN support membrane.

Desalination performance of fabric-structured charged mosaic membrane prepared from poly(vinyl alcohol)-based charged fibers

Charged mosaic (CM) membranes were prepared from fabric structures using two types of poly(vinyl alcohol) (PVA)-based fibers. The fibers were fabricated using anionic and cationic block-type PVA, poly(vinyl alcohol-b-sodium styrene sulfonic acid), and poly(vinyl alcohol-b-vinylbenzyl trimethylammonium chloride). The fabrics were heat pressed to form a nonporous film and crosslinked with glutaraldehyde (GA) to produce fabric-structured CM membranes. Volume flux experiments indicated that the CM membrane exhibited negative osmosis, whereas the uncharged PVA membrane showed positive osmosis. The CM membrane made from the fabric exhibited sufficient mechanical strength for performing a piezodialysis experiment under a pressure of 0.3 MPa. The analytical results of piezodialysis experiments for the CM membrane indicated that the salt flux increased, whereas the water flux remained constant with an increasing initial NaCl concentration. Therefore, the salt-to-water flux ratio increased with increasing NaCl concentration. The CM membrane was desalinated with up to 1500 ppm of NaCl at a pressure of 0.3 MPa. Consequently, the fabricated CM membranes demonstrated the potential for desalinating low-salinity solutions.

Development of High–Pressure Resistant Charged Mosaic Membranes Prepared by Ion–Track Graft Polymerization

Development of High–Pressure Resistant Charged Mosaic Membranes Prepared by Ion–Track Graft Polymerization

Nanostructured Films of Oppositely Charged Domains from Self-Assembled Block Copolymers

The exploration of poly(tert-butyl methacrylate)-block-poly(4-vinylpyridine), PtBMA-b-P4VP, as a precursor material for the creation of nanostructured films with oppositely charged domains is reported. Thin films of hexagonally packed P4VP cylinders were self-assembled perpendicular to the surface and subsequently treated with bromoethane vapor at various times to quaternize pyridinyl nitrogens. The PtBMA matrix was then partially hydrolyzed to poly(methacrylic acid), PMAA, through HCl vapor treatment followed by neutralization by brief submersion in KOH solution. Under optimal treatment conditions, atomic force microscopy and contact angle measurements confirm that the film morphologies remain intact and become more hydrophilic. Time-of-flight secondary ion mass spectrometry confirms the presence and location of specific anions and cations within each domain throughout the block copolymer film and corroborates successful ionization during each treatment step. These results bolster the viability of PtBMA-b-P4VP as a suitable material for creating self-assembled nanostructures bearing oppositely charged domains under relatively facile conditions and open the door to future investigations for their potential application in charged mosaic membranes.

Charged Mosaic Membranes prepared from Ion-track Graft Polymerization and Their Transport Properties

Charged Mosaic Membranes prepared from Ion-track Graft Polymerization and Their Transport Properties

PVA-based Charged Mosaic Membrane with Striped Pattern Prepared by Means of Dispensing Technique

PVA-based Charged Mosaic Membrane with Striped Pattern Prepared by Means of Dispensing Technique

Desalination of Dye by Charged Mosaic Membrane

Desalination and purification of dye can improve its quality and value. Membrane separation technology is one of the main technologies of dye desalination and purification. The charged mosaic membrane (CMM) is prepared by interfacial polymerization (IP) in this paper. And then it is applied in desalination and purification of crude dye. The results shows Rejection of the CMM for NaCl and Reactive Light Yellow (PF-6GS) is 13.2% and 99.2%, respectively. Its flux increases from 6.22 L·m-2·h-1 to 18.5 L·m-2·h-1 when the operating pressure increases from 0.2MPa to 0.5Mpa. Its flux reduces from 13.32 L·m-2·h-1 to 11.11 L· m-2·h-1 and its rejection for NaCl gradually improves from12.5% to 13.7% when NaCl concentration increases from 500 mg·L-1 to 2000mg·L-1. Its flux gradually reduces from 10.17 L·m-2·h-1 to 8.21 L·m-2·h-1 and the rejection for the dye all exceeds 99.00% when the PF-6GS concentration increases from 500mg·L-1 to 2000mg·L-1. After the crude dye is desalinated via five times the NaCl concentration in dye solution reduces from 8775mg·L-1 to 658mg·L-1, the conductivity of dye solution reduces from 28.6 ms/m to 8.92 ms/m, dye purity increases from 72.6% to 97.0%.

Recent Advances in the Fabrication of Membranes Containing "Ion Pairs" for Nanofiltration Processes.

In the face of serious environmental pollution and water scarcity problems, the membrane separation technique, especially high efficiency, low energy consumption, and environmental friendly nanofiltration, has been quickly developed. Separation membranes with high permeability, good selectivity, and strong antifouling properties are critical for water treatment and green chemical processing. In recent years, researchers have paid more and more attention to the development of high performance nanofiltration membranes containing “ion pairs”. In this review, the effects of “ion pairs” characteristics, such as the super-hydrophilicity, controllable charge character, and antifouling property, on nanofiltration performances are discussed. A systematic survey was carried out on the various approaches and multiple regulation factors in the fabrication of polyelectrolyte complex membranes, zwitterionic membranes, and charged mosaic membranes, respectively. The mass transport behavior and antifouling mechanism of the membranes with “ion pairs” are also discussed. Finally, we present a brief perspective on the future development of advanced nanofiltration membranes with “ion pairs”.

A Method for the Efficient Fabrication of Multifunctional Mosaic Membranes by Inkjet Printing.

Most conventional membrane systems are based on size-selective materials that permeate smaller molecules and retain larger ones. However, membranes that can permeate larger molecules more rapidly than smaller ones could find widespread utilization in multiple arenas of technology. Charge mosaic membranes are one example of such a system. Due to their unique nanostructure, which consists of discrete oppositely charged domains, charge mosaics are capable of permeating large dissolved salts more rapidly than smaller water molecules. Here, we present a combined inkjet printing and template synthesis technique to prepare charge mosaic membranes in a rapid and straightforward manner and demonstrate the unique transport properties that result from the mosaic membrane design. Poly(vinyl alcohol)-based composite inks containing poly(diallyldimethylammonium chloride) or poly(sodium 4-styrenesulfonate) were used to pattern positively charged or negatively charged domains, respectively, on the surface of a polycarbonate track-etched membrane with 30 nm pores. The ability to control the net surface charge of the mosaic membranes through the rational deposition of oppositely charged materials was demonstrated and confirmed through nanostructural characterization, electrokinetic measurements, and piezodialysis experiments. Namely, mosaic membranes that possessed an overall neutral charge (i.e., membranes that had equal coverage of positively and negatively charged domains) were capable of enriching the concentration of potassium chloride in the solution that permeated through the membrane. These membranes can be deployed in the many established and emerging nanoscale technologies that rely on the selective transport and separation of ionic solutes from solution. Furthermore, because of the flexibility provided by the membrane fabrication platform, the efforts reported in this work can be extended to other mosaic designs with myriad other functional components.

Zwitterionic functionalized layered double hydroxides nanosheets for a novel charged mosaic membrane with high salt permeability

Charged mosaic membranes containing equivalent cationic and anionic exchange capacities are capable of decreasing the Donnan effect and thus accelerating salts permeation, while maintaining a high rejection of low molecular weight organics. In this study, charged nanosheets zwitterion–hydrotalcite (ZHT) was synthesized by grafting sulfobetaine methacrylate (SBMA) on the surface of positively charged Mg/Al hydrotalcite via surface initiated reverse atom transfer radical polymerization (RATRP). Subsequently, charged mosaic membranes were prepared by embedding different amounts of zwitterion–hydrotalcite into polyethersulfone (PES) casting solution via non-solvent induced phase separation (NIPS). Fourier transforms infrared spectra (FT-IR) and transmission electron microscopy (TEM) indicates that the zwitterion–hydrotalcite was successfully synthesized and well exfoliated. X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), ionic exchange capacity (IEC), surface zeta potential measurement and water contact angle were employed to investigate the effect of ZHT content on overall performance of prepared membranes. It was found that charged mosaic membranes manifested an enhanced ionic exchange capacity, surface hydrophilicity and hydraulic permeability compared to original membrane. Importantly, the charged mosaic membranes presented excellent dyes retention (86.7% for Reactive Red 49), superior salt permeation, and high water flux (80.2Lm−2h−1) under 0.4MPa. Furthermore, the retention of MgCl2, Na2SO4 and NaCl was as low as 9.3%, 7.6% and 0.53%, respectively. It is worth noting that ultra-high salt permeation as a bright spot of charged mosaic membranes could be achieved, which was ascribed to the introduction of zwitterion–hydrotalcite. A mechanism of salt transport through charged mosaic membranes is proposed in this study. Overall, these promising results demonstrate the potential of charged mosaic membranes and suggest their comfortable use in dyes separation.

Mixed mosaic membranes prepared by layer-by-layer assembly for ionic separations.

Charge mosaic membranes, which possess distinct cationic and anionic domains that traverse the membrane thickness, are capable of selectively separating dissolved salts from similarly sized neutral solutes. Here, the generation of charge mosaic membranes using facile layer-by-layer assembly methodologies is reported. Polymeric nanotubes with pore walls lined by positively charged polyethylenimine moieties or negatively charged poly(styrenesulfonate) moieties were prepared via layer-by-layer assembly using track-etched membranes as sacrificial templates. Subsequently, both types of nanotubes were deposited on a porous support in order to produce mixed mosaic membranes. Scanning electron microscopy demonstrates that the facile deposition techniques implemented result in nanotubes that are vertically aligned without overlap between adjacent elements. Furthermore, the nanotubes span the thickness of the mixed mosaic membranes. The effects of this unique nanostructure are reflected in the transport characteristics of the mixed mosaic membranes. The hydraulic permeability of the mixed mosaic membranes in piezodialysis operations was 8 L m(-2) h(-1) bar(-1). Importantly, solute rejection experiments demonstrate that the mixed mosaic membranes are more permeable to ionic solutes than similarly sized neutral molecules. In particular, negative rejection of sodium chloride is observed (i.e., the concentration of NaCl in the solution that permeates through a mixed mosaic membrane is higher than in the initial feed solution). These properties illustrate the ability of mixed mosaic membranes to permeate dissolved ions selectively without violating electroneutrality and suggest their utility in ionic separations.

Preparation of charged mosaic membrane of sodium polystyrene sulfonate and poly(4‐vinyl pyridine) by conjugate electrospinning

ABSTRACTConjugate electrospinning of two nozzles with opposite charges was used for the fabrication of charged mosaic membrane (CM membrane). Sodium polystyrene sulfonate (PNaSS) and poly(4‐vinyl pyridine) (P4VP) were selected as anionic and cationic exchange elements, respectively. Polyvinyl alcohol was used as the common matrix for the enhancement of mechanical properties by formaldehyde crosslinking. Scanning electron microscope (SEM), transmission electron microscope (TEM), and tensile testing for nanofiber were used for the characterizations of CM membrane. Using the conjugate electrospinning, a simple equation was established to predict the mean diameters of nanofibers. It was proved that the calculated diameters fit well with the experimental data using electrospinning parameters such as concentration of spun solution, collecting speed, rate of solution supply, and distance of two nozzles. TEM picture showed a PNaSS nanofiber was incorporated with a P4VP nanofiber. However, SEM photo indicated that the alignment of composite nanofibers in CM membrane was greatly affected by the concentration of polyelectrolyte. As the concentration of PNaSS increased, the alignment degree decreased. After crosslinking with formaldehyde for 20 h, the tensile strength and Young's modulus of CM membrane reached 11.3 and 24.8 MPa, respectively. The water content and water insolubility of CM membrane were also investigated. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40716.

Charge mosaic membranes with semi-interpenetrating network structures prepared from a polymer blend of poly(vinyl alcohol) and polyelectrolytes

Charge mosaic (CM) membranes with semi-interpenetrating network structures were prepared by blending poly(vinyl alcohol) as a membrane matrix, poly(allyl amine) as a polycation and poly(vinyl alcohol-co-2-acrylamido-2-methyl propane sulfonic acid) as a polyanion with varying polyelectrolyte contents under different cross-linking conditions. Our method can prepare CM membranes of a large area easily at low manufacture cost. Although the flux of electrolytes through the membrane is less than that through a typical charge mosaic membrane such as Desalton® (Tosoh Co., Ltd.), which was prepared using micro-phase separation, the permselectivity for electrolytes through the CM membrane was more than 4 times higher than Desalton®. These CM membranes have enough mechanical strength to form thin layer on a porous support membrane, thereby increasing the flux of electrolytes.

From Charge-Mosaic to Micelle Self-Assembly: Block Copolymer Membranes in the Last 40 Years

Different strategies for membrane preparation based on block copolymers are reviewed in this paper, starting from early papers on charge-mosaic membranes and following with dense membranes for gas separation for applications like CO2 separation, pervaporation of aqueous solutions containing organic pollutants, low-fouling surfaces and finally tailoring porous membranes with very sharp pore size distribution. The approaches for manufacture of nanoporous films are summarized, including etching and preferential dissolution. The advantages of a new process based on micelle assembly and phase inversion are emphasized, confirming its perspective of up-scale and application at large scale.

Preparation and Characterization of PVA-based Charge Mosaic Membranes

Preparation and Characterization of PVA-based Charge Mosaic Membranes

Preparation and Characterization of the Tri-Channel Hollow Fiber Charged Mosaic Membrane

Charged mosaic membrane (CMM) has high water flux, low salt retention and high organic rejection. The tri-channel hollow fiber charged-mosaic membrane (CMM) was prepared by interfacial polymerization (IP). The tri-channel polysulfone (PSF) hollow fiber ultrafiltration(UF) membrane was used as the support membrane. Polyethylenimine (PEI), 2, 5-diamino-benzenesulfonic acid (DIA) and basic fuchsin (BF) were used as aqueous phase monomer. Trimesoyl chloride (TMC) was used as organic phase monomer. ATR-IR, scanning electron microscope (SEM) and gas sorption analyzer (GSA) were applied in structural analysis of CMM. The uniform design and SPSS were applied in membrane preparation and data analysis.The polymer ATR-IR spectroscopy shows IP occurrence between aqueous phase monomer and organic phase monomer. Polymer contains both sulfonate group and quaternary ammonium group. It show that the membrane has the feature of CMM. Regression equation was gained, and it shows the CMM retention would enhance with the concentration increase of DIA, PEI and SDS and decrease with concentration decrease of FB in experimental range. The composite layer can be observed from membrane SEM after IP. The CMM retention to NaCl, polyethylene glycol(PEG), Xylenol orange and Methyl chloride is12.4%, 90%, 96%,88% and 88.2% respectively.

Preparation and Characterization of a Novel Polyamide Charged Mosaic Membrane

A novel composite charged mosaic membrane (CCMM) was prepared via interfacial polymerization (IP) of polyamine [poly(epichlorohydrin amine)] and trimesoyl chloride (TMC) on the polyethersulfone (PES) support. Fourier transform infrared spectroscopy (FT-IR), environmental scanning electron microscopy (ESEM), atomic force microscopy (AFM) and water contact angle analysis were applied to characterize the resulted CCMM. The FT-IR spectrum indicates that TMC reacts sufficiently with polyamine. ESEM and AFM pictures show that the IP process produces a dense selective layer on the support membrane. The water contact angle of the CCMM is smaller than that of the substrate membrane because of the cross-linked hydrophilic polyamine network. Several factors affecting the IP reaction and the performance of the CCMM, such as monomer concentration, reaction time, pH value of aqueous phase solution and post-treatment, were studied. The pure water flux of the optimized CCMM is 14.73 L·m −2·h −1·MPa −1 at the operating pressure of 0.4 MPa. The values of separation factor a for NaCl/PEG1000/water and MgCl 2/PEG1000/water are 11.89 and 9.96, respectively. These results demonstrate that CCMM is promising for the separation of low-molecular-weight organics from their salt aqueous solutions.

Synthesis of mosaic membranes and application for egg white protein fractionation by partitioned free-flow isoelectric focusing (FFIEF)

In this article, multi-component protein fractionation was studied by mosaic membrane partitioned free-flow isoelectric focusing (FFIEF). The mosaic membranes were molecularly designed through a blending of aminated poly(2,6-dimethyl-1,4-phenylene oxide) (APPO) and sulfonated polysulfone (SPSf) with polysulfone (PSf). All cast membranes were prepared from the same dope but phase inverted in different coagulants to produce different morphologies. Membrane characterizations through field emission scanning electron microscopy (FESEM) imaging, streaming potential, pore size distribution and PWP (pure water permeation) demonstrated that the self-prepared membranes possessed a variety of membrane structures and charge characteristics. These mosaic membranes were applied in FFIEF as the selective barriers. Experimental results show that a blend of APPO and SPSf with PSf is an effective route to produce highly charged mosaic membranes, which can be used in the separation of five pure protein components from chicken egg white using the mosaic-membrane partitioned FFIEF.

Review of piezodialysis — salt removal with charge mosaic membranes

Piezodialysis (PD) is a process that removes the salt from the water, rather than the other way around as in reverse osmosis (RO). It is not a new process, its long history being one of slow improvement, and its performance not yet near the predictions of 40 or more years ago. Adequate desalting of brackish water has been achieved by PD, but at yields far below acceptable. Some recent publications offering new angles warrant a disinterring of the earlier information. Imperfect membranes are the probable reason for poor performance, the production of the ideal structure representing a challenge for nanoparticle and polymer scientists.