Annealing of Polyelectrolyte Multilayers for Control over Ion Permeation (original) (raw)
Related papers
2014
Polyelectrolyte multilayers (PEMs) for nanofiltration and reverse osmosis are fabricated by means of the Layer by Layer technique from the negatively charged poly(sodium 4-styrenesulfonate) (PSS) and polycations with primary, secondary, tertiary, and quaternary amines. PEMs stability is studied after treatment with the oxidizing agent sodium hypochlorite (NaOCl), in the same conditions as in membrane modulus cleaning. PEM assembly and mass changes after treatment with NaOCl are studied with the Quartz Crystal Microbalance. The chemical composition of the PEMs after the treatment with NaOCl is studied by X-ray photoelectron spectroscopy. The oxidation of polycations in bulk is studied by UV-vis. The PEMs fabricated with poly(diallydimethylammonium chloride) (PDADMAC) and p o l y (v i n y l b e n z y l t r i m e t h y l a m m o n i u m c h l o r i d e) (PVBTMAC), bearing quaternary amines, show the highest chemical stability and smallest mass variations after oxidation. PEMs including other polycations bearing quaternary amines and polycations with primary, secondary, and tertiary amines are either fully removed or significantly changed chemically.
Journal of Membrane Science, 2019
Nanofiltration membranes have limited ion-ion selectivity in water treatment applications, especially when separating ions with similar size and charge. To achieve greater size-based selectivity in nanofiltration, more control of pore structure is required during membrane fabrication. We demonstrate how to tailor membrane pore size and thickness using polyelectrolyte layer-by-layer assembly by alternately applying two strong polyelectrolytes, PDADMAC and PSS, to a polysulfone substrate while systematically controlling the polyelectrolyte and salt concentrations in the deposition solution. Results suggest that increasing polyelectrolyte concentration or salt concentration in the deposition solution increases polyelectrolyte multilayer thickness, but the effects on pore size may be categorized into two distinct regimes. In the first growth regime, increasing polyelectrolyte concentration in the deposition solution led to larger polymer deposition rates and smaller pore sizes. In the second growth regime, increasing polyelectrolyte concentration produced larger pore sizes. We attribute the second regime to less adsorbed polyelectrolyte on the membrane and/or less coiled polymer chains as a result of changing polyelectrolyte-salt interactions. Overall, results show that pore size modification is achievable using layer-by-layer assembly by tuning polyelectrolyte-salt interactions and can be used to study and improve sizebased selectivity in membrane separation processes.
DESALINATION AND WATER TREATMENT
This study discusses the preparation and characterization of polyelectrolyte multilayers deposited on polyacrylonitrile (Pan) and polyethersulfone (Pes) polymer substrates. Emphasis was made on investigating the polyelectrolyte thin film development and the effect of polycation-polyanion combination on bi-layer structural configuration. The membranes performance indicators (water permeability and salt rejection) were determined through laboratory tests. Membrane surfaces were extensively studied with spectroscopic (Fourier transform infrared and X-ray photoelectron spectroscopy) techniques and electrokinetic analysis as well as wettability measurements. It was revealed that subsequent deposition of PEI/PSS or PAH/PSS multilayers resulted in the emergence of new membrane functionality. The Pan substrate was easily modified and allowed the adsorption of polyelectrolyte multilayers due to the presence of amine groups that interacted with the ionized polyions. The ultrathin polyelectrolyte films resulted in favorable interactions between the membrane and water molecules which was due to the increased polar component of the membrane surface free energy. The modified substrates were then tested for their separation properties and they exhibited a good rejection (>85%) for salts of multivalent cations (MgSO 4 and CaCl 2) and an average removal for NaCl and KCl. Salt removal followed this order MgSO 4 > CaCl 2 > NaCl ≥ KCl for all the membranes types. The eventual ion removal was a function of the combined actions of electrostatic and acid-base forces as well as the membrane sieving effect.
Weak polyelectrolyte multilayers as tunable membranes for solvent resistant nanofiltration
Journal of Membrane Science, 2016
This manuscript encompasses the investigation into the solvent resistant nanofiltration (SRNF) performance of multilayer membranes prepared from weak polyelectrolytes. These weak polyelectrolytes are unique in that the charge density is not fixed and depends on the coating pH, adding an extra variable as tuning parameter for SRNF performance. The weak polyelectrolyte based multilayers (PEMs) were prepared on a hydrolyzed PAN support membrane from poly(allylamine hydrochloride) (PAH) as polycation and poly(acrylic acid) (PAA) as polyanion. Detailed investigations on the role of the pH of the coating solution on the performance of the prepared SRNF-membranes were carried out with organic dyes of different size (~300-1000 Dalton) and charge. Variation in pH of the coating solutions was found to lead to a large degree of control over the separation performance of the prepared SRNF-membranes for the different dyes. The solvent permeabilities and the dye retentions were measured and correlated to variations in the PEM membrane structures, with more dye adsorption being found for membranes with more free acid and amine groups. The membranes were also found to be stable for long term-filtrations in solvents such as isopropyl alcohol (IPA), acetonitrile (ACN), tetrahydrofuran (THF) and in the 2 challenging polar aprotic solvent, N,N-dimethylformamide (DMF). Results of this study clearly demonstrate the potential of using pH as tuning parameter for weak PEMs to prepare SRNF-membranes optimized for specific applications. Highlights We present a first example of SRNF membranes based on weak polyelectrolyte multilayers. Within this approach SNRF membrane performance can be tuned by the pH of the multilayer coating solution. Membrane performance is studied in detail with the retention of 5 different organic dyes. Thin and dense membranes with mostly intrinsic charge compensation provide overall better performance. Long term stable membranes for troublesome organic aprotic solvents (THF, DMF and ACN).
Communications in Science and Technology
Thin Film Composite (TFC) Polyelectrolyte Multilayer (PEM) Nanofiltration (NF) membrane consisting of multilayer of Poly(diallyl dimethyl ammonium chloride) (PDAC) and Poly(sodium 4-styrenesulfonate) (PSS) deposited on polyethersulfone (PES) support was prepared using spin-assisted layer by layer assembly (SA-LbL). This work is an effort to discover new material having better characteristics and performance than commercial polyamide (PA) NF membrane. Two main operating conditions namely temperature and salt concentration were investigated and the effect of both on membrane performance was studied. Solution-diffusion Film Model (SDFM) membrane employing two fitting parameters i.e. membrane salt permeability (PS) and stagnant layer salt permeability PS(d), was used to explain membrane transport across the membrane. The result showed an good agreement between experimental and observed rejection rate suggests PEM membrane behaves similar to typical solution diffusion-type composite m...
Nanofiltration using pore-filled membranes: effect of polyelectrolyte composition on performance
Separation and …, 2001
Several series of membranes composed of microporous poly(propylene) substrates filled with polyelectrolyte gels of different chemical structure, polymer concentration and charge densities have been prepared in order to examine the effect of polyelelctrolyte composition on the performance of these membranes in nanofiltration. The membranes were made by two different routes involving either in situ chemical cross-linking of poly(4-vinylpyridine) or poly(vinylbenzyl chloride), or by in situ polymerization of acrylic acid with tetra(ethylene glycol) diacrylate or N,Nmethylenebisacrylamide as cross-linking agents in the pores of the substrates. The resulting pore-filled membranes were characterized by the concentration (volume fraction) of the polyelectrolyte in the pores, ion exchange capacity (charge density), water content, and thickness. The different series of membranes were tested under pressure to determine their hydrodynamic permeabilities and salt separation properties (NaCl). It was found that there was a good correlation between hydrodynamic (Darcy) permeability and gel polymer concentration that holds irrespective of the gel polymer chemistry in the pore-filling gels. Membranes with different pore-filling gels, whether positively or negatively charged, followed the same relationship. The separation properties of the membranes are very good and the salt rejection was found to be practically constant over a wide range of permeabilities (gel concentrations). It was also found that the increase in the nominal charge density above approximately 0.2 mmol/cm 3 of the swollen gel had a negligible effect on the separation properties of the gel-filled membranes. The results of this study provide a basis for the further design and optimization of polyelectrolyte filled membranes for nanofiltration applications.
Journal of Electroanalytical Chemistry, 2017
The layer by layer (LbL) sequential adsorption of oppositely charged polyelectrolytes is a simple tool to form ultrathin multilayer membranes with highly controlled properties. In our studies we have focused on the formation of multilayer films from the pair of synthetic, model polyelectrolytes: poly(allylamine hydrochloride) (PAH)/poly(4-styrenesulfonate) (PSS) and poly(diallyldimethylammonium chloride) (PDADMAC)/poly(4-styrenesulfonate) (PSS) in the presence of monovalent (NaCl) and divalent (MgCl 2) ions solution with the same ionic strength. Quartz crystal microbalance (QCM) was used to determine the film mass. To examine barrier properties of the multilayers two electroactive probes were selected: positively charged hexaammineruthenium (III) chloride and equimolar solution of potassium hexacyanoferrate (II) and potassium hexacyanoferrate (III) of negative charge. We demonstrated that the mass/thickness of the film was larger when the polyelectrolytes were deposited in the presence of divalent ions. On the other hand, the permeability of the polymer films depended not only on the ionic strength, but also on the valence of the ions in the polyelectrolyte solution as well as the charge of the chosen electroactive probe.
Layer-by-Layer Preparation of Polyelectrolyte Multilayer Membranes for Separation
2013
Polymer membranes provide a highly promising platform for the development of an efficient and sustainable technique for separation. Ideally such membranes combine a high flux with a high selectivity requiring thin defect-free membranes. The layer by layer (LBL) assembly technique has proven to be a versatile and simple method for the fabrication of very thin polyelectrolyte multilayers making it highly suitable for the preparation of separation membranes. Recent developments in this field related to membrane preparation and their applications in separation processes are presented and discussed in this review. An overview of the different fabrication techniques of such membranes will be first provided. In addition, the formation mechanism and the parameters that can be varied to tune the properties of the membranes will be discussed. Finally, the potential applications of these membranes in different separation areas such as pervaporation, nanofiltration, solvent resistant nanofiltration, reverse osmosis, gas separation and forward osmosis will be addressed. Pejman Ahmadiannamini obtained his BSc (Chemical Engineering) at University of Isfahan (Iran, 2004). He received his MSc (Chemical Engineering) from Sahand University of Technology (Iran, 2007). In 2008, he moved to KU Leuven (Belgium) and started his PhD at the Center for Surface Chemistry and Catalysis. He is currently a research associate post-doctoral fellow at Dept. of Civil and Environmental Engineering, Michigan State University. His areas of expertise comprise membrane preparation and characterization, solvent resistant nanoltration and environmental application of nanotechnology.
Polyelectrolyte multilayer (PEM) thin films consisting of alternate layers of two PEM systems, that is poly(diallyl dimethyl ammonium chloride)/poly(vinyl sulfate) (PDAC/PVS) and poly(allyl amine hydrochloride) (PAH)/ are successfully deposited on polysulfone (PSF) support using spin-assisted layer-bylayer assembly. The films are characterized using atomic force microscope, Fourier transform Infrared, and contact angle measurement. The salt (NaCl) rejection and water flux of the [PDAC/PVS] and [PAH/PVS] membranes are also evaluated using a crossflow permeation test cell. The permeation test shows that 120 bilayers of [PAH/PVS] on PSF substrate provide salt rejection of 53% and water flux of 37 L/m 2 h, whereas that of PDAC/PVS on PSF substrate provide salt rejection of 21% and water flux of 90 L/m 2 h for a 2000-ppm NaCl solution feed at a pressure of 40 bar and temperature of 25 C.
Indonesian Journal of Science and Technology
Layer-by-Layer (LbL) assembly is considered as the most versatile and robust method in thin-film fabrication. However, its use in the preparation of desalination membrane is still in its infancy. Spin-assisted layer-by-layer assembly (SA-LbL), one of the LbL variants, was selected for the fabrication of a nanofiltration membrane due to its versatility to produce an ultra-thin film with highly controlled film properties within an incredibly short time. Branched-polyethyleneimine (PEI) and poly(sodium 4-styrenesulfonate) (PSS) were employed and alternately deposited on the top of the ultrafiltration polyethersulfone (PES) substrate. PEI/PSS film was then crosslinked using Gluteraldehyd (GA). The resulting membrane was tested at a feed concentration of 2000 ppm NaCl, a pressure of 10 bar, and a temperature of 25°C. Crosslinking time and many layers were varied to investigate the extent of crosslinking and its impact on membrane performance. The permeation test of (PEI/PSS)10 crosslinke...