Journal of Membrane Science 366 (2011) 382–388
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Enhanced performance of inorganic-polyamide nanocomposite membranes prepared by metal-alkoxide-assisted interfacial polymerization Chunlong Kong a , Akira koushima a , Takashi Kamada b , Takuji Shintani b , Masakoto Kanezashi a , Tomohisa Yoshioka a , Toshinori Tsuru a,∗ a b
Department of Chemical Engineering, Hiroshima University, Higashi-Hiroshima, 739-8527, Japan Nitto Denko Corporation 1-1-2, Shimohozumi, Ibaraki, Osaka 567-8860, Japan
a r t i c l e
i n f o
Article history: Received 16 May 2010 Received in revised form 8 October 2010 Accepted 12 October 2010 Available online 16 October 2010 Keywords: Polyamide Metal alkoxide Interfacial polymerization Nanocomposite Permeability
a b s t r a c t A promising strategy is reported for the synthesis of inorganic-polyamide nanocomposite membranes on an ultrafiltration polysulfone support via metal-alkoxide-assisted interfacial polymerization. Three types of nanocomposite membranes were prepared using three different metal alkoxides. The metal alkoxides used here were titanium tetraisopropoxide, bis(triethoxysilyl)ethane and phenyltriethoxysilane. The asprepared nanocomposite membranes exhibited performance superior to that of the pure polyamide membrane. Water flux and salt rejection were observed for each of the nanocomposite membranes. Addition of greater amounts of metal alkoxide to the hexane solution increased both pore size and water flux, which were determined by analysis of the membrane permeation data using aqueous solutions of sodium chloride and organic solutes at a pressure of 1.5 MPa and a temperature of 25 ◦ C. The best nanocomposite membrane that was prepared with phenyltriethoxysilane showed water flux that was increased approximately 2-fold compared with the pure polyamide membrane with negligible rejection loss. © 2010 Elsevier B.V. All rights reserved.
1. Introduction Globally, inadequate water availability and lack of access to fresh water are two of the most significant problems. Membranebased water purification processes are low-cost, energy efficient and environmentally friendly. Reverse osmosis (RO) is an important commercially available membrane technology that is widely used for water purification processes such as desalination and industrial water reuse [1]. However, the currently available polymeric membranes are often limited by the trade-off between permeance/permeability and selectivity [2–5]. RO membranes with higher water permeability, improved rejection and better fouling resistance are needed to reduce both the capital and energy costs of producing a highly purified product. Subsequent to the development of polymeric RO membranes, the design of multilayered thin film composites (TFCs) was an important advancement in membrane science. TFCs are composed of an outer ultra-thin skin polyamide layer (0.1–1 m) fabricated via interfacial polymerization (IP) of m-phenylene diamine in an aqueous phase and trimesoyl chloride in an organic phase, a porous middle polysulfone support, and a non-woven polyester fabric
∗ Corresponding author. Tel.: +81 82 424 7714; fax: +81 82 4247714. E-mail address:
[email protected] (T. Tsuru). 0376-7388/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.memsci.2010.10.026
base [6–11]. These membranes have been widely used in water desalination [12,13]. Continual efforts have been devoted to the innovation of porous supports, polymer reactants and membrane structures [14–17] that improve either the membrane permeance/permeability or selectivity for specific applications or that increase the fouling resistant and chemical/thermal/mechanical stability of membranes [18–22]. For example, polyamide membranes with enhanced water flux and reasonable salt rejection have been prepared by addition of alcohols, sulfur-containing compounds or monohydric aromatic compounds in an aqueous solution and not in an organic phase [23–25]. The efficacy of this strategy has been ascribed to reductions in both the solubility difference and the interfacial tension and to facilitate mass transfer of diamine molecules to the organic phase, which increased the membrane surface roughness [26]. In addition, the additives might have increased the fractional free volume of the prepared membrane, thereby increasing water permeability. On the other hand, a limited number of studies have attempted to control membrane performance by using different types of solvents in the organic phase [27]. Although these methods have their advantages, they are far from satisfactory because membrane performance needs additional improvement. Organic–inorganic polymer membranes that can improve separation, reaction and sorption capacity, as well as enhance chemical and thermal stability, have attracted considerable interest.
C. Kong et al. / Journal of Membrane Science 366 (2011) 382–388
OCH(CH3)2 (CH3)2HCO
Ti
OCH(CH3)2
OCH(CH3)2
OEt
OEt EtO
CH2CH2
Si
Si
OEt OEt
Si
OEt
OEt
TTIP
383
OEt
OEt
BTESE
PhTES
Fig. 1. Chemical structures of titanium tetraisopropoxide (TTIP), bis (triethoxysilyl) ethane (BTESE) and phenyltriethoxysilane (PhTES); (OEt) ethoxy group.
Recently, zeolite NaA, silica and TiO2 nanoparticles were rationally incorporated into the polyamide layer, which enhanced membrane permeability compared with that of a pure polyamide membrane [28–31]. The incorporated nanoparticles might have provided a direct path for water transport or modified the membrane network structure, thereby increasing water permeability. Although this innovative concept has drawn a great deal of attention, there remain difficulties associated with implementation of this strategy: dispersion of nanoparticles in a nonpolar organic solvent and control of nanoparticles within a thin polymer layer. Nanoparticles readily aggregate when mixed with a nonpolar solvent. On the other hand, metal alkoxides readily dissolve in an organic solvent (hexane). Therefore, fabrication of inorganic-polyamide nanocomposite membranes by the addition of a metal alkoxide to the hexane phase prior to interfacial IP is possible. The performance of the resultant membranes might be superior to that of membranes fabricated from nanoparticles because the metal alkoxide, which is more thoroughly dispersed in the hexane phase, can be hydrolyzed and produce smaller inorganic nanoparticles and an organic alcohol either during or after IP. Previous reports indicate that this process is useful for high-performance-membrane formation. Herein, we report a promising strategy for the fabrication of inorganic-polyamide nanocomposite membranes using three types of metal alkoxides (Fig. 1). Small particles or silica networks can be produced after hydrolysis reaction, dehydrolysis reaction or condensation reaction, which may control the network pore-size of the resultant membranes. The primary objective of this work was to prepare nanocomposite membranes with enhanced performance in terms of either membrane permeance or selectivity. The inorganic-polyamide composite membranes were examined using thermo-gravimetric analysis (TGA). The surface morphology of the as-prepared membranes was observed using scanning electron microscopy (SEM). The structure of a membrane cross-section was examined using transmission electron microscopy (TEM). These characteristics were then compared with the membrane permeability properties that were measured using permeation equipment
and aqueous solutions containing either an inorganic salt or organic solutes at a temperature of 25 ◦ C and a pressure of 1.5 MPa. 2. Experimental 2.1. Materials The chemicals, 1,3,5-benzenetricarbonyl trichloride (TMC, Aldrich), titanium tetra isopropoxide (TTIP, Aldrich), 1,3phenylenediamine (MPD, Aldrich), bis (triethoxy silyl) ethane (BTESE, Aldrich), phenyl triethoxy silane (PhTES, Aldrich), were used without further purification. All other chemicals were analytical grade. Ultrafiltration polysulfone (PSF) membranes were used as the support. The SEM image (Fig. 2) shows that the pore size distribution of the PSF support was less than 30 nm. 2.2. Synthesis of the nanocomposite membrane Each of the pure polyamide membranes and the inorganicpolyamide nanocomposite membranes was hand-cast on a PSF support by polymerization of the aromatic MPD with the acid chloride TMC. The inorganic-polyamide nanocomposite membranes were prepared using a novel metal-alkoxide-assisted interfacial polymerization method. The detailed process was as follows. First, an aqueous solution of 2 wt% MPD and 0.15 wt% sodium lauryl sulfate was allowed to cover the top of the PSF support for 2 min. The excess solution was then drained from the support surface, which was blotted with pieces of filter paper at room temperature. Solutions of TMC (0.1 wt%) in hexane containing a metal alkoxide at concentrations ranging from 0 to 5 wt% were poured onto the PSF support. After a predetermined polymerization period, the organic solution was drained off. The as-prepared membrane was dried in air at room temperature for 3–5 min to remove excess organic
100
60
40
Increase
Weight residue (%)
80
TTIP-polyamide BTESE-polyamide PhTES-polyamide Pure polyamide
20
0
0
100
200
300
400
500
600
Temperature (℃)
Fig. 2. SEM image of the ultrafiltration polysulfone membrane used as the nanocomposite membrane support.
Fig. 3. TGA curves of the pure polyamide membrane and the nanocomposite membranes prepared using the metal-alkoxide-assisted IP method. The content of metal-alkoxide was 1 wt% for all nanocomposite membranes.
C. Kong et al. / Journal of Membrane Science 366 (2011) 382–388
75
-1
25
2
Nanocomposite membrane (5 wt% PhTES) 60
9
-12
Permeability (10
50
Rejection (%)
-12
Permeability (10
4
80
12
Pure polyamide membrane 6
40
3
20
Rejection (%)
6
100
15
-1
100
m Pa s )
8
-1
-1
m Pa s )
384
(a) 0
1
2
3 PhTES (wt %)
4
0
5
10
50
100
150
0 200
IP time (s) Fig. 5. Permeability properties of the pure polyamide membrane and the nanocomposite membrane as a function of the IP time.
100
12
2.3. Characterization
80
-1
-1
m Pa s )
0
0
0
Permeability (10
-12
60 6 40
Rejection (%)
8
4 20
2
(b) 0
0 0.0
0.2
0.4
0.6
0.8
1.0
BTESE (wt %) 15
Each membrane used for morphologic analysis of the active layer was rinsed with DI water, and then was dried under vacuum at 30 ◦ C for 12 h. SEM images were obtained using a JEOL S5200 scanning electron microscope. The membrane cross-section samples were prepared by immersing the membranes in ethanol, t-butyl alcohol, and then freeze-drying. After freeze-drying, the membranes were dyed by a RuO4 vapor at room temperature for 5 min, followed by embedding and curing in epoxy resin and finally cutting by an ultramicrotome. The samples were observed on a TEM (Hitachi H-7650, Japan). The thin active polyamide layer was obtained by dissolving the PSF support in a cyclohexanone solution, followed by drying (80 ◦ C) overnight for TGA analysis (TGA 50, Shimadzu, Japan). Samples (∼5 mg) were heated from room temperature to about 600 ◦ C at a rate of 5 ◦ C/min.
100
12
80
9
60
6
40
3
20
Rejection (%)
Permeability (10
-12
-1
-1
m Pa s )
2.4. Membrane permeability performance test
(c) 0
0 0.0
0.2
0.4
0.6
0.8
1.0
Permeability tests were performed in a high-pressure chemical resistant stirred cell. The effective membrane area was 5.1 cm2 . Both the rejection and solution flux of each inorganic salt or organic solute were evaluated for both the nanocomposite membranes and the pure polyamide membranes. All permeation results were obtained using an aqueous solution of 2000 ppm (wt%) NaCl and 500 ppm of each organic solute (IPA, s-butanol, glucose or maltose) at a pressure of 1.5 MPa and a temperature of 25 ◦ C. Both the electric conductivity rejection of the inorganic salts and the total carbon (TC) rejection of the organic solutes were measured using a conductivity meter (ES-12, Horiba, Japan) and a TOC-VE (Shimadzu, Japan), respectively. Rejection and water permeability were calculated using the following equations:
TTIP (wt %) Fig. 4. Permeability and rejection of the nanocomposite membranes as a function of metal-alkoxide loading: (a) PhTES; (b) BTESE; (c) TTIP.
rejection =
cp 1− cf
water permeability = solvent. Finally, the nanocomposite membrane was rinsed with deionized water (DI). The TMC, metal alkoxide and hexane mixture was prepared in a glove box under vacuum as follows. First, specific amounts of TMC and metal alkoxide were added to a predetermined volume of hexane solution, and the solution was then ultrasonicated for 15 min. The pure polyamide membrane was made using the same process without addition of a metal alkoxide.
× 100
(1)
v t · P · s
(2)
in which cp (mg/l) is the concentration of salt or organic solute on the permeation side, cf (mg/l) is the concentration of inorganic salt or organic solute on the feed side, v is the permeation volume (m3 ), t is the permeation time (s), P is the pressure difference across the membrane (Pa), and s is the effective membrane area (m2 ).
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Fig. 6. SEM images of the pure polyamide membrane (A) and the nanocomposite membranes prepared by metal-alkoxide-assisted interfacial polymerization. (B) PhTES (5 wt%); (C) BTESE (0.1 wt%); (D) TTIP (0.1 wt)%.
3. Results and discussion 3.1. TG analysis The inorganic-polyamide nanocomposite membranes and the pure polyamide membrane were subjected to TGA under an air atmosphere, and the results are shown in Fig. 3. All samples showed
significant weight loss at temperatures ranging from 400 to 550 ◦ C. The temperature range of the nanocomposite membranes was similar to that of the pure polyamide membrane. The similar thermal decomposition temperature of the membrane samples indicates that the polymer backbone chains were minimally affected by the metal alkoxides. The weight loss that occurred below 200 ◦ C was mainly due to the elimination of excessive organic materials
Fig. 7. TEM cross-sectional images of the pure polyamide membrane (A) and the nanocomposite membrane (PhTES, 5 wt%) (B).
C. Kong et al. / Journal of Membrane Science 366 (2011) 382–388
10
3.3. SEM and TEM The surface morphologies of the pure polyamide membrane and the nanocomposite membranes were observed using SEM micrographs of the samples (Fig. 6). The pure polyamide membrane clearly shows the typical valley and ridge structure, which is identi-
8
80
6
60
4
40
2
20
0
3.2. Permeability performance based on NaCl aqueous solution
0
IPA
S-butanol
Permeability
Maltose Glucose Rejection
Pure polyamide membrane 10
100
-12
-1 -1 m Pa s )
Permeability 8
Rejection 80
6
60
4
40
2
20
0
Rejection (%)
b
Permeability ( 10
Fig. 4 shows the water permeance/permeability and rejection of sodium chloride for the nanocomposite membranes with different metal-alkoxide-content loadings, which were fabricated using the metal-alkoxide-assisted IP method. The precision of the permeability and rejection measurements was estimated to be within ±10% and ±1%, respectively. The water flux of each nanocomposite membrane was significantly increased at higher metal-alkoxide loadings. An interesting and striking result was that a trade-off between water permeability and rejection was not apparent as the PhTES loading increased. The rejection of sodium chloride for the as-prepared membranes was 95–98%, while the water permeability increased markedly from 2.1 × 10−12 m Pa−1 s−1 to 5.0 × 10−12 m Pa−1 s−1 . However, the permeability of the nanocomposite membranes fabricated by addition of BTESE or TTIP increased significantly from 2.1 × 10−12 m Pa−1 s−1 to 5.9 × 10−12 m Pa−1 s−1 and 2.1 × 10−12 m Pa−1 s−1 to 7.8 × 10−12 m Pa−1 s−1 , respectively. However, a significant reduction in salt rejection was also observed when the loading content of BTESE or TTIP was greater than 0.2 wt%. For example, the membranes fabricated by addition of 1.0 wt% BTESE or TTIP showed moderate salt rejection—60% and 55%, respectively. These results indicate that metal alkoxides might modify the network structures of the as-prepared membranes, leading to variation in the membrane transport properties based on the types of metal alkoxide loaded. Fig. 5 shows the relationship between the time courses of water permeability and salt rejection versus IP reaction time. Clearly, the modified membrane network structures with high water flux were fabricated by addition of PhTES to the hexane phase. The rejection increased and water permeability decreased gradually for both membranes up to a certain IP reaction time, after which the rejection and permeability remained unchanged. The rejection difference between the membranes was diminished at longer IP reaction times (more than 1 min), whereas the difference in water flux between the membranes remained. The permeation results suggest that the rate of metal-alkoxide hydrolysis might determine nanocomposite membrane performance [33]. The substitution group of the metal alkoxide might also have a significant influence on the nanocomposite membrane performance. This hypothesis warrants further investigation.
100
Rejection (%)
-1 -1 m Pa s )
a
-12
derived from the initial IP process, while the steady weight loss in the range of 200–550 ◦ C was attributed to further decomposition of the polyamide polymer [32]. The metal oxide content of the composites was directly related to the mass of the residue obtained at about 550 ◦ C. The weight of the sample residue was increased by adding metal alkoxides, whereas the weight residue of the pure polyamide membrane was approximately zero at 600 ◦ C. It can be seen that the weight residue varied among the membranes as follows: PhTES < BTESE < TTIP. One possible explanation for this result is the difference in reaction rates among the loaded metal alkoxides. Higher reaction rates resulted in a larger weight residue. It should be noted that the amount of inorganic material incorporated was low because the membrane layer formed within a narrow reaction zone. Therefore, the weight residue of each membrane was less than 15 wt%, although the metal-alkoxide content (1 wt%) was much higher than that of TMC.
Permeability ( 10
386
0
IPA
S-butanol
Glucose
Maltose
Nanocomposite membrane (PhTES, 5 wt%) Fig. 8. Permeability properties of the pure polyamide membrane and the nanocomposite membrane for a series of neutral organic solutions of different molecular sizes at a temperature of 298 K and a pressure of 1.5 MPa.
cal to the morphology of commercial membranes [26]. Apparently, the surface morphology of the nanocomposite membranes was altered by loading with PhTES, BTESE or TTIP. A unique structure was observed on the surface of the nanocomposite membrane fabricated by addition of PhTES, whereas the membranes prepared by addition of BTESE or TTIP exhibited smoother surface morphologies. This result accorded with the incorporation of silica particles in the polyamide membrane [29]. The differences in membrane surface morphology might be related to the difference in pore size of the as-prepared membranes. The resultant membranes showed different permeability properties, which were clearly revealed by the tests of permeability to the sodium chloride aqueous solution (Fig. 4). The structures of cross-sections of the nanocomposite membrane fabricated by addition of PhTES and of the pure polyamide membrane are evident in the TEM images (Fig. 7). It should be noted that globules, which were probably the crosssections of ridge-and-valley structure of PA layer, were observed on the PSF support. Since PA was dyed by RuO4 and epoxy resin and
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It should be noted that the Ferry model also predicted approximately the same rejection values as the hindered-diffusion model. The increased pore size enhanced water permeation due to less friction with the membrane pore wall.
100
0.5nm 80
Rejection (%)
0.65nm 4. Conclusions 60
40
Nanocomposite Pure polyamide Hindered Diffusion
0.85nm 20
Ferry 0 0
0.2
0.4
0.6
0.8
1
1.2
2rs (nm) Fig. 9. Rejection of organic solutes of different molecular sizes for the pure polyamide membrane and the nanocomposite membrane (PhTES, 5 wt%.). (Curves are calculated using the hindered diffusion and Ferry models, points are experimental.)
PSF were observed in gray, the white parts of globules are just space, suggesting no permeation resistance the inside of ridges. Overall, PA dense layers were observed not only on the surface of the PSF support but also as the skin layer of the globules. The thickness of the dense layer of the nanocomposite membrane was similar to that of the pure polyamide membrane, whereas the surface roughness was altered (Fig. 6). These results suggest that either the membrane surface roughness was altered or the pore size was enlarged, which resulted in a high water flux. Thus, the permeation of the as-prepared nanocomposite membranes supports a new strategy for the design of high-performance inorganic-polymer composite membranes. 3.4. Permeability performance based on organic solutes The rejection of the pure polyamide membrane and of the nanocomposite membrane were tested using a series of neutral organic solutions that differed in molecular size (isopropyl alcohol (IPA); s-butanol; glucose; maltose) to estimate the pore size distribution [34,35]. Fig. 8 clearly shows that the pure polyamide membrane almost completely (94–99%) rejected large organic solutes dissolved in water. However, small solutes, i.e., molecular size less than s-butanol, which is slightly larger than a water molecule, resulted in moderate rejection by the nanocomposite membrane. This result indicates that the nanocomposite membrane had a larger pore size, which resulted in a higher water flux. In order to examine the change in membrane morphology, membrane pore sizes were estimated by fitting rejection data of different solutes to transport models. According to the Ferry equation [36], rejection by a sieving membrane with a uniform pore size (i.e., diameter) can be expressed simply as R = [1 − (1 − ds /dp )2 ]2 × 100, where R is the percent rejection, ds is the solute diameter, and dp is the diameter pore size of the membrane. In the hindered diffusion model, which has been used for characterization of polyamide membranes, rejections are formulated in a more complicated manner [37–40]. In both models, Stokes radii were used for solute sizes, ds , which can be calculated from the diffusivities. From the observed percent rejections of the organic solutes and their estimated diameters that were determined according to the best fit with the hindered diffusion model, the mean pore size of the pure polyamide membrane was estimated to be 0.65 nm and that of the nanocomposite membrane was estimated to be 0.85 nm (Fig. 9).
In summary, an inorganic-polyamide nanocomposite membrane with high water permeability and salt rejection was prepared on an ultrafiltration PSF support using a promising metal-alkoxideassisted interfacial polymerization method. The permeation tests of sodium chloride in an aqueous solution indicate that the permeance/permeability of the nanocomposite membranes was increased significantly at higher metal-alkoxide (PhTES) loadings with no rejection loss. The SEM tests indicated that the surface morphologies of the nanocomposite membranes were altered by loading with PhTES, BTESE or TTIP to improve the network structure of the nanocomposite membrane. The mean pore size of the best nanocomposite membrane was estimated to be 0.85 nm, whereas the pore size of the pure polyamide membrane was approximately 0.65 nm. In summary, this promising method effectively controlled both nanocomposite membrane formation and permeability performance. Compared with the pure polyamide membrane, the as-prepared membranes showed improved water desalination and purification performance. The strategy employed in the present study allows for more robust design of nanocomposite membrane properties. References [1] M.E. Suk, A.V. Raghunathan, N.R. Aluru, Fast reverse osmosis using boron nitride and carbon nanotubes, Appl. Phys. Lett. 92 (2008) 133120. [2] X.S. Peng, J. Jin, Y. Nakamura, T. Ohno, L. Ichinose, Ultrafast permeation of water through protein-based membranes, Nat. Nanotechnol. 4 (2009) 353. [3] Y. Li, T.S. Chung, S. Kulprathipanja, Novel Ag+ -zeolite/polymer mixed matrix membranes with a high CO2 /CH4 selectivity, AIChE J. 53 (2007) 610. [4] T. Tsuru, Inorganic porous membranes for liquid phase separation, Sep. Purif. Meth. 30 (2001) 191. [5] B.D. Freeman, Basis of permeability/selectivity tradeoff relations in polymeric gas separation membranes, Macromolecules 32 (1999) 375. [6] R.J. Petersen, Composite reverse osmosis and nanofiltration membranes, J. Membr. Sci. 83 (1993) 81. [7] J.E. Cadotte, R.J. Petersen, R.E. Larson, E.E. Erickson, A new thin film composite sea water reverse osmosis membrane, Desalination 32 (1980) 25. [8] M. Kurihara, Y. Fusaoka, T. Sasaki, R. Bairinji, T. Uemura, Development of crosslinked fully aromatic polyamide ultra-thin composite membranes for seawater desalination, Desalination 96 (1994) 133. [9] M. Kurihara, T. Uemura, Y. Nakagawa, T. Tonomura, The thin film composite low pressure reverse osmosis membranes, Desalination 54 (1985) 75. [10] W.G. Light, J.L. Perlman, A.B. Riedinger, D.F. Needham, Desalination of nonchlorinated surface sea water using TFC membrane elements, Desalination 70 (1988) 47. [11] R.L. Riley, H.K. Lonsdale, C.R. Lyons, Compositemembranes for seawater desalination by reverse osmosis, J. Appl. Polym. Sci. 15 (1971) 1267. [12] C.S. Slater, R.C. Ahlert, C.G. Uchrin, Applications of reverse osmosis to complex industrial wastewater treatment, Desalination 48 (1983) 171. [13] D. Bhattacharyya, M. Jevtitch, J.K. Ghosal, J. Kozminsky, Reverse osmosis membrane for treating coal-liquefaction wastewater, Environ. Prog. 3 (2) (1984) 95. [14] K. Yoon, B.S. Hsiao, B. Chu, High flux nanofiltration membranes based on interfacially polymerized polyamide barrier layer on polyacrylonitrile nanofibrous scaffolds, J. Membr. Sci. 326 (2009) 484. [15] L. Li, S. Zhang, X. Zhang, Preparation and characterization of poly (piperazineamide) composite nanofiltration membrane by interfacial polymerization of 3,3 ,5,5 -biphenyl tetraacyl chloride and piperazine, J. Membr. Sci. 335 (2009) 133. [16] B.J.A. Tarboush, D. Rana, T. Matsuura, H.A. Arafat, R.M. Narbaitz, Preparation of thin-film-composite polyamide membranes for desalination using novel hydrophilic surface modifying macromolecules, J. Membr. Sci. 325 (2008) 166. [17] S.J. Lue, S.H. Peng, Polyurethane (PU) membrane preparation with and without hydroxypropyl--cyclodextrin and their pervaporation characteristics, J. Membr. Sci. 222 (2003) 203. [18] S.Y. Kwak, M.O. Yeom, I.J. Roh, D.Y. Kim, J.J. Kim, Correlations of chemical structure, atomic force microscopy (AFM) morphology, and reverse osmosis (RO) characteristics in aromatic polyester high-flux RO membranes, J. Membr. Sci. 132 (1997) 183.
388
C. Kong et al. / Journal of Membrane Science 366 (2011) 382–388
[19] S.Y. Kwak, D.W. Ihm, Use of atomic force microscopy and solid-state NMR spectroscopy to characterize structure-property-performance correlation in high-flux reverse osmosis (RO) membranes, J. Membr. Sci. 158 (1999) 143. [20] A.P. Rao, S.V. Joshi, J.J. Trivedi, C.V. Devmurari, V.J. Shah, Structure- performance correlation of polyamide thin film composite membranes: effect of coating conditions on film formation, J. Membr. Sci. 211 (2003) 13. [21] S.V. Joshi, P.K. Ghosh, V.J. Shah, C.V. Devmurari, J.J. Trivedi, P. Rao, CSMCRI experience with reverse osmosis membranes and desalination: case studies, Desalination 165 (2004) 201. [22] P.S. Singh, S.V. Joshi, C.V. Devmurari, J.J. Trivedi, A.P. Rao, P.K. Ghosh, Probing the structural variations of thin film composite RO membranes obtained by coating polyamide over polysulfone membranes of different pore dimensions, J. Membr. Sci. 278 (2006) 19. [23] T. Yamaguchi, K. Ikeda, Composite reverse osmosis membrane and production thereof, U.S. Patent 5,160,619 (1992). [24] M. Hirose, K. Ikeda, Method of producing high permeable composite reverse osmosis membrane, U.S. Patent 5,576,057 (1996). [25] M. Hirose, H. Ito, M. Maeda, K. Tanaka, Highly permeable composite reverse osmosis membrane, method of producing the same, and method of using the same, U.S. Patent 5, 614, 099 (1997). [26] S.H. Kim, E.Y. Kwak, T. Suzuki, Positron annihilation spectroscopic evidence to demonstrate the flux-enhancement mechanism in morphology-controlled thin- film-composite (TFC) membrane, Environ. Sci. Technol. 39 (2005) 1764. [27] A.K. Ghosh, E.M.V. Hoek, Impacts of support membrane structure and chemistry on polyamide-polysulfone interfacial composite membranes, J. Membr. Sci. 336 (2009) 140. [28] M.L. Lind, B.-H. Jeong, A. Subramani, X.F. Huang, E.M.V. Hoek, Effect of mobile cation on zeolite-polyamide thin film nanocomposite membranes, J. Mater. Res. 24 (2009) 1624. [29] M.L. Lind, A.K. Ghosh, A. Jawor, X.F. Huang, W. Hou, Y. Yang, E.V.H. Hoek, Influence of zeolite crystal size on zeolite-polyamide thin film nanocomposite membranes, Langmuir 25 (2009) 10139.
[30] G.L. Jadav, P.S. Singh, Synthesis of novel silica-polyamide nanocomposite membrane with enhanced properties, J. Membr. Sci. 328 (2009) 257. [31] H.S. Lee, S.J. Im, J.H. Kim, H.J. Kim, J.P. Kim, Polyamide thin-film nanofiltration membranes containing TiO2 nanoparticles, Desalination 219 (2008) 48. [32] J.S. Liu, T.W. Xu, M. Gong, Y.X. Fu, Fundamental studies of a new hybrid (inorganic–organic) positively charged membrane. II. Membrane preparation via alcoholysis reaction and amination processes of silicone and titanate coupling agents, J. Membr. Sci. 264 (2005) 87. [33] N. Kim, D.H. Shin, Y.T. Lee, Effect of silane coupling agents on the performance of RO membranes, J. Membr. Sci. 300 (2007) 224. [34] T. Tsuru, M. Urairi, S.-I. Nakao, S. Kimura, Reverse osmosis of single and mixed electrolytes with charged membranes: experiment and analysis, J. Chem. Eng. Jpn. 24 (1991) 518. [35] X. Wang, T. Tsuru, S. Nakao, S. Kimura, The electrostatic and steric-hindrance model for the transport of charged solutes through nanofiltration membranes, J. Membr. Sci. 135 (1997) 19. [36] P. Aimar, M. Meireles, V. Sanchez, A contribution to the translation of retention curves into pore size distributions for sieving membranes, J. Membr. Sci. 54 (1990) 321. [37] W.M. Deen, Hindered transport of large molecules in liquid-filled pores, AIChE J. 33 (1987) (1987) 1409. [38] H. Saidain, N. Bn Amar, J. Palmeri, A. Deratni, Interplay between the transport of solutes across nanofiltration membranes and the thermal properties of thin active layer, Langmuir 26 (2010) 2574. [39] N. Ben Amar, H. Saidani, A. Deratani, J. Palmeri, Effect of temperature on the transport of water and neutral solutes across nanofiltration membranes, Langmuir 23 (2007) 2937. [40] W.R. Bowen, A.W. Mohammad, N. Hila, Characterization of nanofiltration membranes for predictive purpose-use of salts, uncharged solutes and atomic force microscopy, J. Membr. Sci. 126 (1997) 91.