The Experts below are selected from a list of 1533 Experts worldwide ranked by ideXlab platform
Sanchuan Yu - One of the best experts on this subject based on the ideXlab platform.
-
improving fouling resistance and chlorine stability of Aromatic Polyamide thin film composite ro membrane by surface grafting of polyvinyl alcohol pva
Desalination, 2015Co-Authors: Qing Chen, Lizhong Wang, Sanchuan YuAbstract:Abstract Improving fouling resistance and chlorine stability of Aromatic Polyamide (PA) thin-film composite (TFC) reverse osmosis membrane is still of considerable need in desalination membrane technology. Here, we reported the chemical linkage of neutral hydrophilic polymer polyvinyl alcohol (PVA) on the surface of a commercial PA TFC membrane through a single step of grafting with potassium persulfate as thermal dissociation initiator and its role on the improvement of membrane resistance to both chlorine and fouling. Membrane characterization was conducted through ATR-FTIR spectroscopy, SEM, AFM, measurements of streaming potential and contact angle and cross-flow permeation tests. It was found that membrane surface became smoother, more hydrophilic and less charged after modification and the modified membrane exhibited an increased slat rejection, a slightly declined water flux and improved fouling resistances to the model foulants of bovine serum albumin (BSA), sodium dodecyl sulfate (SDS) and dodecyltrimethyl ammonium bromide (DTAB). The chlorine exposure tests under accelerated conditions also indicated that the membrane chlorine stability has been enhanced effectively. The PVA molecules on the membrane surface could effectively enhance membrane anti-adsorption capability and prevent the underlying Polyamide backbones from chlorine attack, and thereby improving membrane resistance to both fouling and chlorine.
-
modification of Aromatic Polyamide thin film composite reverse osmosis membranes by surface coating of thermo responsive copolymers p nipam co am i preparation and characterization
Journal of Membrane Science, 2010Co-Authors: Dihua Wu, Sanchuan YuAbstract:This study focuses on the surface modification of the commercial Aromatic Polyamide (PA) thin-film composite (TFC) reverse osmosis (RO) membranes with thermo-responsive copolymers poly(N-isopropylacrylamide-co-acrylamide) (P(NIPAM-co-Am)) for improved membrane properties. Firstly, thermo-responsive copolymers P(NIPAM-co-Am) with certain lower critical solution temperature (LCST) were synthesized by free radical copolymerization in aqueous solution. The resultant copolymers were then used to modify the commercial TFC RO membranes through surface coating technique under different conditions, and the surface properties of the resulting modified membranes were characterized by ATR-FTIR, XPS, SEM, AFM, and contact angle measurement. Finally, the reverse osmosis performance of the modified RO membranes was evaluated by permeation experiment with salt aqueous solution. The experimental results revealed that thermo-responsive copolymer P(NIPAM-co-Am) could be successfully deposited on the surface of the commercial Aromatic Polyamide TFC RO membrane by dip-coating method under certain conditions and the surface hydrophilicity of the modified membrane would change with the environmental temperature; that while the deposited copolymer P(NIPAM-co-Am) surface layer tended to offer additional resistance to permeation, the increased surface hydrophilicity would compensate for the reduction in membrane permeability; and that the surface coating layer of copolymer P(PNIAM-co-Am) had little influence on the salt rejection of the modified TFC membrane.
Seungyeop Kwak - One of the best experts on this subject based on the ideXlab platform.
-
design of tio2 nanoparticle self assembled Aromatic Polyamide thin film composite tfc membrane as an approach to solve biofouling problem
Journal of Membrane Science, 2003Co-Authors: Sung Ho Kim, Seungyeop Kwak, Byeonghyeok Sohn, Tai Hyun ParkAbstract:Abstract Microbial biofouling is one of the major obstacles for reaching the ultimate goal to realize high permeability over a prolonged period of reverse osmosis operation. In this study, the hybrid thin-film-composite (TFC) membrane consisted of self-assembly of TiO2 nanoparticles with photocatalytic destructive capability on microorganisms was devised as a novel means to reduce membrane biofouling. Then, the anti-fouling and fouling mitigation on the actual commercialized TFC was verified. TiO2 nanoparticles of a quantum size (∼10 nm or less) in anatase crystal structure were prepared from the controlled hydrolysis of titanium tetraisopropoxide and characterized by X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM). Hybrid thin-film-composite (TFC) membrane was prepared by self-assembly of the TiO2 nanoparticles through coordination and H-bonding interaction with the COOH functional group of Aromatic Polyamide thin-film layer, which was ascertained by X-ray photoelectron spectroscopy (XPS). The hybrid membrane was shown to possess the dramatic photobactericidal effect on Escherchia coli (E. coli) under UV light illumination. Finally, introduction of TiO2 nanoparticles on the actual commercial TFC membrane and application of RO field test after exposure to microbial cells verified a substantial prevention against the microbial fouling by showing less loss of RO permeability, offering a strong potential for possible use as a new type of anti-biofouling TFC membrane.
-
structure motion performance relationship of flux enhanced reverse osmosis ro membranes composed of Aromatic Polyamide thin films
Environmental Science & Technology, 2001Co-Authors: Seungyeop Kwak, Soo Gyung Jung, Sung Ho KimAbstract:The present paper explores the role of dimethyl sulfoxide (DMSO) used as an additive to modify the morphological as well as the molecular nature of Aromatic Polyamide during the formation of thin-film-composite (TFC) membranes. In addition, it elucidates the mechanism of enhancing the reverse osmosis (RO) permeation of the resulting membranes in proportion to the addition of DMSO. Morphological studies by atomic force microscopy (AFM) observed that as the concentration of DMSO increased, the surface roughness and the surface area of the Aromatic Polyamide TFC membranes became higher and larger, compared to FT-30 membrane for which DMSO was not added during interfacial reaction. Such morphological changes were brought about from fluctuating interface through reducing the immiscibility between aqueous/organic phases by DMSO and provided more opportunities to have contact with water molecules on the surface, participating in the enhancement of the water permeability. Chemical composition studies by X-ray photoelectron spectroscopy (XPS) revealed that there was a considerable increase of the cross-linked amide linkages relative to the linear pendant carboxylic acid groups in the TFC membranes of more DMSO addition. The increase of such amide linkages as hydrogen bonding sites facilitated the diffusion of water molecules through the thin films and played a favorable role in elevating water flux without considerable loss of salt rejection. Relaxation and motion analyses by 1H solid-state nuclear magnetic resonance (NMR) spectroscopy also confirmed the XPS revelation on the basis of measurements of the spin-lattice relaxation time in the rotating frame, T1rho, and determination of the correlation time, tau(c), for the Aromatic Polyamides forming thin films. The trend of longer tau(c)'s with the increase of DMSO concentration reflected the thin-film Aromatic Polyamides of less locally mobile chains, accompanied by the higher degree of cross-linking and, hence, the greater number of amide groups. The combined results of AFM, XPS, and solid-state NMR provided a robust explanation for the mechanism of flux enhancement of the Aromatic Polyamide TFC membranes with the addition of DMSO, which would contribute to not only a fundamental understanding of the process but also an advanced designing of the so-called "tailor-fit" TFC membranes.
-
hybrid organic inorganic reverse osmosis ro membrane for bactericidal anti fouling 1 preparation and characterization of tio2 nanoparticle self assembled Aromatic Polyamide thin film composite tfc membrane
Environmental Science & Technology, 2001Co-Authors: Seungyeop Kwak, Sung Ho Kim, Soon Sik KimAbstract:Hybrid organic/inorganic reverse osmosis (RO) membranes composed of Aromatic Polyamide thin films underneath titanium dioxide (TiO2) nanosized particles have been fabricated by a self-assembly process, aiming at breakthrough of biofouling problems. First, positively charged particles of the colloidal TiO2 were synthesized by a sol−gel process, and the diameter of the resulting particles in acidic aqueous solution was estimated to be ≈2 nm by analyzing the UV−visible absorption characteristics with a quantum mechanical model developed by Brus. Transmission electron microscopy (TEM) further confirmed the formation of the quantum-sized TiO2 particles (∼10 nm or less). The TiO2 particles appeared to exist in the crystallographic form of anatase as observed with the X-ray diffraction (XRD) pattern in comparison with those of commercial 100% rutile and commercial 70:30% anatase-to-rutile mixture. The hybrid thin-film-composite (TFC) Aromatic Polyamide membranes were prepared by self-assembly of the TiO2 nanopar...
-
details of surface features in Aromatic Polyamide reverse osmosis membranes characterized by scanning electron and atomic force microscopy
Journal of Polymer Science Part B, 1999Co-Authors: Seungyeop Kwak, Soo Gyung Jung, Young Seo Yoon, Dae Woo IhmAbstract:In the present article, some new events on the surface morphology of the Aromatic Polyamide thin-film-composite (TFC) membranes were demonstrated in con- junction with their inherent chemical nature. In addition, the detailed, quantitative understanding of the microscopic surface features was shown to be essential in con- trolling the water permeability and eventually developing the high performance mem- branes. The surface roughness and the surface area were mainly affected by the existence or nonexistence of the crosslinking and/or the free amide groups not pertinent to the formation of the hydrogen bonding, which in turn contributed to the water permeability. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1429 -1440, 1999
-
use of atomic force microscopy and solid state nmr spectroscopy to characterize structure property performance correlation in high flux reverse osmosis ro membranes
Journal of Membrane Science, 1999Co-Authors: Seungyeop KwakAbstract:Abstract Morphology and relaxation studies were very effective in understanding of the reverse osmosis (RO) permeation for the high-flux reverse osmosis (RO) membranes which were the thin-film-composite (TFC) type based on Aromatic Polyamide of m-phenylene diamine (MPD)/trimesoyl chloride (TMC). Microscopic morphology analyzed by atomic force microscopy (AFM) together with field-emission scanning electron microscopy (FE-SEM) and molecular relaxation characterized by solid-state 1 H nuclear magnetic resonance (NMR) spectroscopy revealed an important factor crucially affecting the enhancement of RO permeability. The proton spin-lattice relaxation in the rotating frame for the Aromatic Polyamides in their wet state (i.e., saturated with D2O) has been shown to be sensitive to the water flux and played a significant role in enhancing the membrane permeability, regardless of the surface features. The Aromatic Polyamide possessing relatively shorter spin-lattice relaxation times in the rotating frame, T1ρ, provided a TFC membrane with higher RO permeation, and vice versa.
Nadia A Mohamed - One of the best experts on this subject based on the ideXlab platform.
-
thermal degradation behaviour of novel wholly para oriented Aromatic Polyamide hydrazides containing sulfone ether linkages
Polymer Degradation and Stability, 2009Co-Authors: Noura Yahya Almehbad, Nadia A MohamedAbstract:Abstract Thermal stability and degradation behaviour of a series of novel wholly para-oriented Aromatic Polyamide–hydrazides containing flexibilising sulfone–ether linkages in their main chains have been investigated in nitrogen and in air using differential scanning calorimetry (DSC), thermogravimetry (TG), infrared spectroscopy (IR) and elemental analysis. All of these polymers have similar structural formula except for the presence of sulfone, ether, or sulfone–ether linking groups between appropriate Aromatic nuclei in their main chains. The influence of incorporation of these linkages on the thermal stability and degradation behaviour of these polymers has also been studied. The polymers were prepared by a low temperature solution polycondensation reaction of 4-amino-3-hydroxybenzhydrazide (4A3HBH) and an equimolar amount of either 4,4′-sulfonyl dibenzoyl chloride (SDBC), 4,4′-[sulfonyl bis (1,4-phenylene)dioxy] dibenzoyl chloride (SODBC), 4,4′-[sulfonyl bis (2,6-dimethyl- 1,4-phenylene)dioxy] dibenzoyl chloride (4MeSODBC), or 4,4′-(1,4-phenylenedioxy)dibenzoyl chloride (ODBC) in anhydrous N,N -dimethyl acetamide (DMAc) as a solvent at −10 °C. A related Polyamide–hydrazide without the flexibilising linkages is also investigated for comparison. It was synthesized from 4A3HBH and terephthaloyl chloride (TCl) by the same synthetic route. The results clearly reveal that these polymers are characterized by high thermal stability. Their weight loss occurred in three distinctive steps. The first was small and was assigned to the evaporation of absorbed moisture. The second was appreciable and was attributed to the cyclodehydration reaction of the o-hydroxy Polyamide–hydrazides into the corresponding poly (1,3,4-oxadiazolyl-benzoxazoles) by losing water. This is not a true degradation, but rather a thermo-chemical transformation reaction. The third was relatively severe and sharp, particularly in air, and corresponded to the decomposition of the resulting poly(1,3,4-oxadiazolyl-benzoxazoles). There is a slight shift of the decomposition temperature of these polymers to a lower temperature as the sulfone–ether linkages were introduced into the polymer chains. The decomposition seems to start by breaking the sulfonyl groups as confirmed from DSC measurements. The results also indicate that the incorporation of the flexibilising linkages into the polymer main chains did not seem to significantly influence the thermal stability of these polymers in comparison with that of the polymer free from these linkages.
-
structure property relationships for novel wholly Aromatic Polyamide hydrazides containing various proportions of para phenylene and meta phenylene units iii preparation and properties of semi permeable membranes for water desalination by reverse osm
European Polymer Journal, 2003Co-Authors: Nadia A Mohamed, Abeer Obaid Hamad AldossaryAbstract:Abstract Flat sheet asymmetric reverse osmosis membranes were successfully prepared from N , N -dimethylacetamide (DMAc) solutions of a series of novel wholly Aromatic Polyamide–hydrazides that contained different amounts of para - and meta -phenylene rings. These Polyamide–hydrazides were synthesized by a low temperature solution polycondensation reactions of either 4-amino-3-hydroxybenzhydrazide or 3-amino-4-hydroxybenzhydrazide with an equimolar amount of either terephthaloyl dichloride [TCl], isophthaloyl dichloride [ICl] or mixtures of various molar ratios of TCl and ICl in anhydrous DMAc as a solvent. All the polymers have the same structural formula except of the way of linking phenylene units inside the polymer chains. The content of para - to meta -phenylene moieties was varied within these polymers so that the changes in the latter were 10 mol% from polymer to polymer, starting from an overall content of 0–100 mol%. All the membranes were characterized for their salt rejection (%) and water permeability (cm 3 cm −2 day −1 ) of 0.5 N aqueous sodium chloride feed solution at 3924 kPa operating pressure. The effects of polymers structural variations together with several processing parameters to achieve the best combination of high selectivity and permeability were studied. Effects of various processing parameters of the membranes on their transport properties were investigated by varying the temperature and period of the solvent evaporation of the cast membranes, coagulation temperature of the thermally treated membranes, annealing of the coagulated membranes, casting solution composition, membrane thickness and the operating pressure. During the thermal treatment step, the asymmetric structure of the membranes with a thin dense skin surface layer supported on a more porous layer was established. The former layer seems to be responsible for the separation performance. The results obtained showed that membrane performance was very much influenced by all of the examined processing variables and that membranes with considerably different properties could be obtained from the same polymer sample by using different processing parameters. Thus, the use of higher temperatures and longer exposure times in the protomembrane forming thermal treatment step would result in a membrane of lower solvent content and with a thicker skin layer and consequently led to higher salt rejection at lower water permeability. Most significantly, the membrane properties clearly depended on the polymer structure. Under identical processing condition, substitution para -phenylene rings for meta -phenylene ones within the polymer series resulted in an increase in salt rejection capability of the membranes. This may be attributed to an increase in their chain symmetry associated with increased molecular packing and rigidity through enhanced intermolecular hydrogen bonding. This produces a barrier with much smaller pores that would efficiently prevent the solute particles from penetration. Coagulation temperature controls the structure (porosity) of the membrane particularly its supported layer and consequently its water permeability. Moreover, annealing of the prepared membranes in deionized water at 100 °C was found essential for useful properties in the single-stage separation applications, which required optimum membrane selectivity. Upon annealing, the membrane shrinks resulting in reducing its pore size particularly in the skin layer and consequently improving the salt rejection. Addition of lithium chloride to the casting solution produced a membrane with increased porosity and improved water permeability. Salt rejection capability of the membranes is clearly affected by the applied pressure, reaching its maximum at nearly 4000 kPa. Furthermore, the water permeability is inversely proportional to the membrane thickness, while the salt rejection is not substantially influenced.
-
structure property relationships for novel wholly Aromatic Polyamide hydrazides containing various proportions of para phenylene and meta phenylene unitsii thermal stability and degradation behaviour
Polymer Degradation and Stability, 2003Co-Authors: Nadia A Mohamed, Abeer Obaid Hamad AldossaryAbstract:Abstract The influences of controlled structural differences and molecular weight on the thermal stability and degradation behaviour of a series of novel wholly Aromatic Polyamide-hydrazides have been investigated in nitrogen and in air using differential scanning calorimetry (DSC), thermogravimetric analysis (TG), infrared spectrophotometry (IR) and elemental analysis. The structural variations of the polymers were achieved by varying the content of the meta - and para -substituted phenylene moieties incorporated into their chains. All the polymers were synthesized by a low temperature solution polycondensation reaction of either 4-amino-3-hydroxybenzhydrazide [4A3HBH] or 3-amino-4-hydroxybenzhydrazide [3A4HBH] with an equimolar amount of either terephthaloyl chloride [TCl], isophthaloyl chloride [ICl] or mixtures of various molar ratios of TCl and ICl in anhydrous N , N -dimethylacetamide [DMAc] as a solvent at −10 °C. The content of para - and meta -phenylene moieties was varied within this series so that the changes in the latter were 10 mol% from polymer to polymer, starting from an overall content of 0–100 mol%. All the polymers have the same structural formula except for the way of linking phenylene units in the polymer chain. The results showed that these polymers have high resistance to elevated temperatures. Their weight loss occurred in three steps. The first was small and was attributed to evaporation of adsorbed surface water. The second was considerable and was assigned to cyclodehydration reactions of the Polyamide-hydrazides into the corresponding poly(1,3,4-oxadiazolyl-benzoxazoles) with loss of water. This is not a true degradation, but rather a thermochemical transformation reaction. The third was relatively severe and steep, particularly in air, and corresponded to the decomposition of the polymers. The results clearly indicate that substitution of para -phenylene units for meta -phenylene ones within this polymer series leads to improved polymer stability at elevated temperatures in nitrogen as well as in air. This should be associated with regularity of supermolecular packing within the bulk of the investigated polymers wherein the colinear arrangement of the para -phenylene units should allow for establishment of stronger intermolecular bonds which would be more difficult to break and therefore more resistant to high temperatures. Moreover, Polyamide-hydrazides having different molecular weights were also examined. The results clearly reveal that at all temperatures used and in both degradation atmospheres all the investigated samples exhibited similar thermal behaviour regardless of their molecular weights, except in the temperature range 160–200 °C where the lower molecular weight samples showed significant weight losses which may be attributed to hydrogen bonded DMAc. This indicates that structural building units of these polymers (which contained characteristic groups, such as: Aromatic rings and amide and hydrazide linking bonds in the case of Polyamide-hydrazides and Aromatic nuclei, 1,3,4-oxadiazolyl rings and benzoxazolyl moieties in the case of poly(1,3,4-oxadiazolyl-benzoxazoles) are responsible for their high thermal stability, rather than the longer chain segments.
Congjie Gao - One of the best experts on this subject based on the ideXlab platform.
-
Modification of PSf/SPSf Blended Porous Support for Improving the Reverse Osmosis Performance of Aromatic Polyamide Thin Film Composite Membranes
'MDPI AG', 2018Co-Authors: Li-fen Liu, Xin Xie, Xiao-xiao Song, Congjie GaoAbstract:In this study, modification of polysulfone (PSf)/sulfonated polysulfone (SPSf) blended porous ultrafiltration (UF) support membranes was proposed to improve the reverse osmosis (RO) performance of Aromatic Polyamide thin film composite (TFC) membranes. The synergistic effects of solvent, polymer concentration, and SPSf doping content in the casting solution were investigated systematically on the properties of both porous supports and RO membranes. SEM and AFM were combined to characterize the physical properties of the membranes, including surface pore natures (porosity, mean pore radius), surface morphology, and section structure. A contact angle meter was used to analyze the membrane surface hydrophilicity. Permeate experiments were carried out to evaluate the separation performances of the membranes. The results showed that the PSf/SPSf blended porous support modified with 6 wt % SPSf in the presence of DMF and 14 wt % PSf had higher porosity, bigger pore diameter, and a rougher and more hydrophilic surface, which was more beneficial for fabrication of a Polyamide TFC membrane with favorable reverse osmosis performance. This modified PSf/SPSf support endowed the RO membrane with a more hydrophilic surface, higher water flux (about 1.2 times), as well as a slight increase in salt rejection than the nascent PSf support. In a word, this work provides a new facile method to improve the separation performance of Polyamide TFC RO membranes via the modification of conventional PSf porous support with SPSf
-
enhancing the performance of Aromatic Polyamide reverse osmosis membrane by surface modification via covalent attachment of polyvinyl alcohol pva
Journal of Membrane Science, 2016Co-Authors: Fang Yan, Yalan Shi, Congjie GaoAbstract:Abstract Surface modification is a promising way to improve membrane performance. In this study, a commercial Aromatic Polyamide thin-film composite reverse osmosis membrane was modified through sequential surface treatment with glutaraldehyde aqueous solution followed by polyvinyl alcohol (PVA) aqueous solution. ATR-FTIR spectroscopy, SEM, AFM, measurements of streaming potential and contact angle and cross-flow permeation tests were employed to investigate the influence of modification on membrane performance. It was illustrated that PVA molecules were covalently attached on the surface of the pristine membrane and both membrane surface physico-chemical and permeation properties could be tuned through changing the PVA content. The covalent attachment of PVA resulted in an improved surface hydrophilicity, a declined surface negative charge and a slightly increased surface roughness, and could enhance membrane salt rejection and water flux simultaneously. The modification was proved to be effective in improving membrane antifouling property to the foulants of bovine serum albumin, sodium dodecy sulfate and dodecyltrimethyl ammonium bromide through increasing anti-adsorption capability and in enhancing membrane chlorine stability through reducing chlorination sites and preventing the underlying Polyamide backbones from chlorine attack. Furthermore, the modification could effectively enhance the membrane rejection performance and antifouling property in tertiary treatment of industrial effluent.
Sung Ho Kim - One of the best experts on this subject based on the ideXlab platform.
-
design of tio2 nanoparticle self assembled Aromatic Polyamide thin film composite tfc membrane as an approach to solve biofouling problem
Journal of Membrane Science, 2003Co-Authors: Sung Ho Kim, Seungyeop Kwak, Byeonghyeok Sohn, Tai Hyun ParkAbstract:Abstract Microbial biofouling is one of the major obstacles for reaching the ultimate goal to realize high permeability over a prolonged period of reverse osmosis operation. In this study, the hybrid thin-film-composite (TFC) membrane consisted of self-assembly of TiO2 nanoparticles with photocatalytic destructive capability on microorganisms was devised as a novel means to reduce membrane biofouling. Then, the anti-fouling and fouling mitigation on the actual commercialized TFC was verified. TiO2 nanoparticles of a quantum size (∼10 nm or less) in anatase crystal structure were prepared from the controlled hydrolysis of titanium tetraisopropoxide and characterized by X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM). Hybrid thin-film-composite (TFC) membrane was prepared by self-assembly of the TiO2 nanoparticles through coordination and H-bonding interaction with the COOH functional group of Aromatic Polyamide thin-film layer, which was ascertained by X-ray photoelectron spectroscopy (XPS). The hybrid membrane was shown to possess the dramatic photobactericidal effect on Escherchia coli (E. coli) under UV light illumination. Finally, introduction of TiO2 nanoparticles on the actual commercial TFC membrane and application of RO field test after exposure to microbial cells verified a substantial prevention against the microbial fouling by showing less loss of RO permeability, offering a strong potential for possible use as a new type of anti-biofouling TFC membrane.
-
structure motion performance relationship of flux enhanced reverse osmosis ro membranes composed of Aromatic Polyamide thin films
Environmental Science & Technology, 2001Co-Authors: Seungyeop Kwak, Soo Gyung Jung, Sung Ho KimAbstract:The present paper explores the role of dimethyl sulfoxide (DMSO) used as an additive to modify the morphological as well as the molecular nature of Aromatic Polyamide during the formation of thin-film-composite (TFC) membranes. In addition, it elucidates the mechanism of enhancing the reverse osmosis (RO) permeation of the resulting membranes in proportion to the addition of DMSO. Morphological studies by atomic force microscopy (AFM) observed that as the concentration of DMSO increased, the surface roughness and the surface area of the Aromatic Polyamide TFC membranes became higher and larger, compared to FT-30 membrane for which DMSO was not added during interfacial reaction. Such morphological changes were brought about from fluctuating interface through reducing the immiscibility between aqueous/organic phases by DMSO and provided more opportunities to have contact with water molecules on the surface, participating in the enhancement of the water permeability. Chemical composition studies by X-ray photoelectron spectroscopy (XPS) revealed that there was a considerable increase of the cross-linked amide linkages relative to the linear pendant carboxylic acid groups in the TFC membranes of more DMSO addition. The increase of such amide linkages as hydrogen bonding sites facilitated the diffusion of water molecules through the thin films and played a favorable role in elevating water flux without considerable loss of salt rejection. Relaxation and motion analyses by 1H solid-state nuclear magnetic resonance (NMR) spectroscopy also confirmed the XPS revelation on the basis of measurements of the spin-lattice relaxation time in the rotating frame, T1rho, and determination of the correlation time, tau(c), for the Aromatic Polyamides forming thin films. The trend of longer tau(c)'s with the increase of DMSO concentration reflected the thin-film Aromatic Polyamides of less locally mobile chains, accompanied by the higher degree of cross-linking and, hence, the greater number of amide groups. The combined results of AFM, XPS, and solid-state NMR provided a robust explanation for the mechanism of flux enhancement of the Aromatic Polyamide TFC membranes with the addition of DMSO, which would contribute to not only a fundamental understanding of the process but also an advanced designing of the so-called "tailor-fit" TFC membranes.
-
hybrid organic inorganic reverse osmosis ro membrane for bactericidal anti fouling 1 preparation and characterization of tio2 nanoparticle self assembled Aromatic Polyamide thin film composite tfc membrane
Environmental Science & Technology, 2001Co-Authors: Seungyeop Kwak, Sung Ho Kim, Soon Sik KimAbstract:Hybrid organic/inorganic reverse osmosis (RO) membranes composed of Aromatic Polyamide thin films underneath titanium dioxide (TiO2) nanosized particles have been fabricated by a self-assembly process, aiming at breakthrough of biofouling problems. First, positively charged particles of the colloidal TiO2 were synthesized by a sol−gel process, and the diameter of the resulting particles in acidic aqueous solution was estimated to be ≈2 nm by analyzing the UV−visible absorption characteristics with a quantum mechanical model developed by Brus. Transmission electron microscopy (TEM) further confirmed the formation of the quantum-sized TiO2 particles (∼10 nm or less). The TiO2 particles appeared to exist in the crystallographic form of anatase as observed with the X-ray diffraction (XRD) pattern in comparison with those of commercial 100% rutile and commercial 70:30% anatase-to-rutile mixture. The hybrid thin-film-composite (TFC) Aromatic Polyamide membranes were prepared by self-assembly of the TiO2 nanopar...