- Email: [email protected]
Effect of NaA zeolite particle addition on poly(phthalazinone ether sulfone ketone) composite ultrafiltration (UF) membrane performance
Journal of Membrane Science 345 (2009) 5–12
Contents lists available at ScienceDirect
Journal of Membrane Science journal homepage: www.elsevier.com/locate/memsci
Effect of NaA zeolite particle addition on poly(phthalazinone ether sulfone ketone) composite ultrafiltration (UF) membrane performance Runlin Han, Shouhai Zhang, Cheng Liu, Yutian Wang, Xigao Jian ∗ College of Chemical Engineeering, Dalian University of Technology, Dalian 116012, PR China
a r t i c l e
i n f o
Article history: Received 20 May 2009 Received in revised form 24 July 2009 Accepted 28 July 2009 Available online 12 August 2009 Keywords: Poly(phthalazinone ether sulfone ketone) NaA zeolite particles Ultrafiltration membrane Hydrophilicity
a b s t r a c t PPESK is of particular interest in the fabrication of UF membrane for its considerable mechanical strength, thermal stability and chemical resistance. However, its use in aqueous phase is restricted due to its hydrophobicity. NaA zeolite is one of most hydrophilic inorganic material with low atom ratio of Si:Al (1:1) and big channel diameter and good comprehensive performance which may have the potential to improve the properties of PPESK. Composite ultrafiltration (UF) membranes with entrapped NaA zeolite particles were prepared from poly(phthalazinone ether sulfone ketone) (PPESK). The membranes were prepared with phase inversion process and were characterized by UF experiments and scanning electron microscope (SEM) observations. At 3 wt.% NaA content, the composite membranes held excellent water permeability, hydrophilicity and good antifouling ability with enhanced retentions. Higher NaA content (than 3 wt.%) caused a particle aggregation to some extent according to the cross-section and external surface morphology. However, the excess incorporation of the zeolite particles did not cause decline of membrane performance according to the UF experiments. Antifouling performance was tested with resistance-in-series Model and flux decline in Titan Yellow dye solution. Thermal analysis (DSC) was performed in order to investigate the interactions between NaA particles and PPESK. PPESK UF membranes with different molecular weight cut-off (MWCO) and high flux were obtained by adjusting the polymer concentration. It was concluded that the membrane prepared in our laboratory had better performance than two kinds of commercial UF membranes. © 2009 Elsevier B.V. All rights reserved.
1. Introduction PPESK is one of the most attractive polymer materials for separation membranes, notable for its excellent thermal stability, extraordinary mechanical properties, high chemical resistance and good solubility [1–4]. However, it has a limited antifouling ability induced by its hydrophobic nature. Some efforts have been made to improve the hydrophilicity and separation performances of PPESK membranes. Modification of PPESK by sulfonation with concentrated or fuming sulfuric acid as sulfonation agents was carried out to prepare membrane materials with increased hydrophilicity and potentially increased fouling resistance [5]. Thin film composite (TFC) membranes were prepared from sulfonated SPPESK as a top layer coated onto PPESK UF support membranes [6]. Quaternized PPESK and amphiphilic graft copolymer consisting of PPESK backbones and PEG comb-like side chains (PPESK-gPEG) were synthesized [7,8]. High molecular weight additive like
∗ Corresponding author. Tel.: +86 411 83653426; fax: +86 411 83639223. E-mail address: [email protected] (X. Jian). 0376-7388/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.memsci.2009.07.052
poly(vinyl pyrrolidone) (PVP) was used to enhance the porosity and hydrophilic performance of the PPESK UF membrane [9]. Inorganic membranes can offer better chemical, thermal and antifouling resistance. It is unfortunate that the significant spread of commercial applications has been limited. They remain expensive and brittle, with poor separation performance and membrane forming ability compared with organic membrane [10]. In recent years, inorganic particles have attracted great attention for the modification of separation membrane. Inorganic materials that often could be blended with polyvinylidene fluoride (PVDF) and polysulfone (PSf) include silica (SiO2 ) [11], zirconium dioxide (ZrO2 ) [12], alumina (Al2 O3 ) particles [13], titanium dioxide (TiO2 ) [14,15] and other inorganic materials were also studied for special function [16–18]. PPESK UF membrane was modified by uniformly dispersing inorganic TiO2 nanoparticles in the PPESK casting solution. The comprehensive performances of the membrane were enhanced by TiO2 addition. The membrane hydrophilicity and surface wettability were enhanced due to the introduction of hydrophilic TiO2 particles. Permeability and rejection experiments showed that the pure water flux and solute rejection of the membranes were remarkably elevated when less amount of TiO2 was
6
R. Han et al. / Journal of Membrane Science 345 (2009) 5–12
Fig. 1. Chemical structure of poly(phthalazine ether sulfone ketone) (PPESK).
2. Experimental 2.1. Materials and instruments
Fig. 2. Morphology of NaA zeolite particles.
added [19]. Zeolites are microporous crystalline materials, routinely used as catalysts, ion-exchangers and absorbents because of their chemical structure. NaA zeolite was considered to be one of the most hydrophilic inorganic membrane materials and was widely used as pervaporation composite membrane material or desiccant agent [20]. NaA zeolite particles are generally stable in a range of aqueous and organic solvents, so they should not wash out rapidly [21,22]. However, there was no report about utilizing NaA zeolite particles to improve antifouling ability of PPESK and other UF membrane materials. So PPESK matrix UF membranes with entrapped NaA particles were prepared to enhance the performance of PPESK UF membrane. The effects of the NaA addition on the membrane morphologies and performances were investigated by SEM, UF experiments and antifouling test.
PPESK (sulfone:ketone = 1:1, [] = 0.56 dL/g) was provided by Dalian New Polymer Co. (PR China) and its chemical structure was showed in Fig. 1. N,N-Dimethylacetamide (DMAc) and polyethyleneglycol (PEG 10,000, PEG 6000 and PEG 2000) were analytical grade and used as received. NaA zeolite particles were provided by Ph.D. Wei Xiao (Inorganic membrane laboratory, Dalian university of technology). Synthesis method of NaA zeolite particles was followed as Ref. [23] and it was characterized with SEM (JSM-5600L, JEOL, Japan) and X-ray diffraction (XRD) with a Philips Analytical X-ray diffractometer using Cu K␣ radiation under 40 kV and 100 mA. The interaction was analyzed with DSC (DSC822, METTLER TOLEDO, Switzerland). The membrane feed solution side was stirred magnetically to reduce concentration polarization. A flat-sheet dead-end membrane cell (Ecological Environment Center of Chinese Academy of Science) having an effective separation area of 41 cm2 and a feed volume of 500 mL was used in all membrane flux characterization and separation experiments. Spectrophotometer 752 PC (Shanghai Spectrum Instrument Co., Ltd., Shanghai, China) was employed for measuring the concentration of PEG and Titan Yellow dye. 2.2. Membrane preparation NaA zeolite particles after being dried 2 h at 120 ◦ C were added to the casting suspension. The amount of NaA varied as 0, 1, 2, 3, 4 and 5 wt.% by weight of the casting suspension while PPESK was fixed 15 wt.%. Then these samples were labeled as N1, N2, N3, N4, N5 and N6, respectively. The membranes were cast on a horizontal glass plate with a glass blade to make it about 200 m thick. After evaporation 10 s in the air, the membranes were precipitated by immersing them in a water bath at 6–8 ◦ C. The membranes have to be rinsed with deionized water before use. The influence to the membrane performance and morphology were studied by adjusting the NaA content and PPESK concentration. 2.3. Membrane characterization The membranes were characterized in the dead-end membrane module after they were pretreated under the pressure of 0.2 MPa for 30 min. The pure water flux and the rejection of PEG and Titan Yellow dye from its 100 mg/L solution were measured under the pressure of 0.1 MPa at ambient temperature. The permeation flux, J, is calculated as follows: J=
Fig. 3. XRD patterns of NaA zeolite.
W At
(1)
where W is the total weight of the water or solution permeated during the experiment; A is the membrane area; and t is the operation time. Rejection, R, is calculated using the following
R. Han et al. / Journal of Membrane Science 345 (2009) 5–12
7
Table 1 Composition of membranes from N1 to N6. Membrane
N1
N2
N3
N4
N5
N6
PPESK (wt.%) NaA (wt.%) DMAc (wt.%)
15 0 85
15 1 84
15 2 83
15 3 82
15 4 81
15 5 80
2.4. Membrane morphology The morphologies of the cross-section and external surface of asymmetric membranes were observed with a SEM. The samples were fractured in liquid nitrogen and sputtered with gold after they were immersed with ethanol and hexane to observe the structure of the membranes. Fig. 4. Effect of NaA content on the performance of PPESK UF membrane.
2.5. Membrane fouling evaluation equation:
R=
Cp 1− Cf
%
(2)
where Cp and Cf are the concentration of the permeate solution and the feed solution, respectively. All the experiments on flux and rejection were repeated for three times. The Relation Standard Deviation of the data was lower than 15%.
The degree of membrane fouling was calculated quantitatively using the resistance-in-series model [26,27]: J=
TMP Rt
(3)
where J is the flux (L/m2 h); TMP the transmembrane pressure (0.35 MPa); and the viscosity of solution at room
Fig. 5. Effect of NaA content on the external surface morphology of PPESK UF membranes.
8
R. Han et al. / Journal of Membrane Science 345 (2009) 5–12
temperature. Rt = Rm + Rf + Rc
(4)
A modification to this model had been applied in this research to differentiate between pore plugging, chemically reversible (i.e. cake layer removed by NaOCl backwash) and readily reversible (i.e. cake layer removed by cross-flow washing with DIW) cake resistances as follows: Rf = Ric + Rp
(5)
where Rm is the intrinsic membrane resistance; Rf is the sum of the resistances caused by solute adsorption into the membrane pores or walls and chemically reversible cake. Rc is the cake resistance formed by cake layer deposited over the membrane surface. Ric is the resistance due to chemically reversible cake and Rp is the resistance due to pore plugging. Resistance values can be obtained through the following equations: Rm =
Rf = Rp =
DI water · Jiw
DI water · Jiw
TMP − (Rm + Rp + Ric ) BSA · J
Jiw , Jfw , JBW and J are flux values determined experimentally. Jiw is the initial deionized water flux before ultrafiltration, Jfw is final deionized water flux after removing cake layer by cross-flow washing, JBW is the deionized water flux after removing chemically reversible cake layer by backwash with 100 ppm NaOCl, and J is flux with bovine serum albumin (BSA) (a 1 g/L bovine serum albumin solution in phosphate buffered saline (PBS) at 20 ◦ C and at pH 7.4). Filtration and washing time were all controlled 10 min in this work. Flux decline study for the dye filtration process was also studied with the Titan Yellow dye solution to evaluate the antifouling property of the prepared membranes with entrapped NaA particles. 3. Results and discussions 3.1. Characterization of NaA zeolite particles
TMP
TMP
Rc =
− Rm
TMP − Rm DI water · JBW
It can be seen from Fig. 2 that all NaA particles with the mean diameter of 2 m are essentially symmetrical. The XRD patterns of the synthesized NaA zeolite in Fig. 3 are compared with standard NaA zeolite crystals and the pick and relative intensities are very compatible with the standard pattern. So they both confirmed that the particles utilized in this work were pure NaA zeolite.
Fig. 6. Effect of NaA content on the cross-section morphology of PPESK UF membranes.
R. Han et al. / Journal of Membrane Science 345 (2009) 5–12 Table 2 Filtration resistances of the N1 and N4 membranes.
N1 N4
Rm /Rt (%)
Rf /Rt (%)
Rc /Rt (%)
Rc /Rf (%)
21 31
67 52
12 17
18 33
Fig. 7. Antifouling performance of N1 and N4 (tested with Titan Yellow dye).
9
adsorbed water vapor in the air. So in the evaporation stage delayed liquid–liquid demixing occurred in the nascent membrane surface which caused a more dense skin layer formed [24]. The reasons for the decrease of pure water flux and the increase of rejection were that the performance of membranes was controlled by the overall porosity and the pore size in the external surface. When the membrane top surfaces were magnified at 2000 times in Fig. 5, it can be observed that the external surfaces of the membrane became tough. The cross-section displayed obvious finger-like pores and the skin layer became thin when NaA zeolite particles were added according to Fig. 6. It is clear that on increasing NaA concentration, the fingerlike structure becomes narrow and its number also decreases. At the same time, its asymmetric structure became more obvious with macrovoids in the sublayer. This may be induced by that NaA particles were very hydrophilic. As soon as the membrane immersed into water, NaA would strongly adsorb water which caused instantaneous liquid–liquid demixing. So it yielded a dense top layer and lower flux which could be demonstrated in Fig. 4. This phenomenon was similar with the results of PEG 1000 is a hydrated compound with high hydrophilicity, and it can enhance the hydrophilicity of the PPESK casting solution. Thus, the gelation rate increases with the increased concentration of PEG 1000 [25]. However, the flux of N6 decreased only 28% compared with N1 because of the super hydrophilicity of NaA particles. Furthermore, water can permeate through the hydrophilic and microporous NaA particles while PEG cannot. So the composite membranes showed elevated rejection and comparatively high flux. When NaA content was raised to 4 wt.%, NaA agglomerates were observed in the micrographs of the cross-section and surface of PPESK UF membrane which could be observed in Fig. 5. But it did not indicate the performance deterioration of the membranes according to Fig. 4. In fact, NaA content had been raised to 6 wt.%, however the membrane performance was quickly deteriorated with much flaw which might be caused by the strong agglomerates. 3.3. Antifouling performance comparison of N1 and N4
Fig. 8. DSC analysis of N1 and N4.
3.2. Effect of NaA content on the performance of PPESK UF membrane The polymer content was fixed on 15 wt.% and the effect of NaA content on membrane performance and morphology was studied by varying the NaA content. The composition of the membrane was listed in Table 1. As could be seen in Fig. 4, the PEG 6000 rejection increased from 77.1 to 96.8% and the pure water flux decreased slightly from 340 to 246 L/m2 h when NaA content in the casting suspension changed from 0 to 5 wt.%. This implied that the membrane surface became more dense which caused higher rejection and lower flux. It was often believed that additives like PVP, PEG and LiCl did not increase the rejection of the UF membrane. But in this work, NaA zeolite was used as additive which strongly
3.3.1. Resistance study in the filtration Based on the resistance-in-series model, the total resistance is the sum of the intrinsic membrane, cake layer and solute adsorption into the membrane pores and walls resistances. A modification of this model has been applied in this research to account for the readily reversible cake (Rrc ), chemically reversible cake (Ric ) and pore plugging (Rp ) resistances. Table 2 shows the resistance percentage value of BSA filtrations by membranes N1 and N4. The percentage contribution of cake layer resistance to the total resistance was 12 and 17% and percentage contribution of solute adsorption to the total resistance was 67 and 52% for N1 and N4, respectively. So the
Table 3 Composition of membranes from N7 to N13. Membrane
N7
N8
N9
N10
N11
N12
N13
PPESK (wt.%) NaA (wt.%) DMAc (wt.%)
12 3 85
13 3 84
14 3 83
15 3 82
16 3 81
17 3 80
18 3 79
Fig. 9. Effect of polymer concentration on the performance of the membranes.
10
R. Han et al. / Journal of Membrane Science 345 (2009) 5–12
higher value of Rc /Rf of N4 according the modified resistance-inseries model showed that N4 had better hydrophilicity than N1. The hydrophilic NaA particles in the membrane surface and membrane pores can account for the conclusion. 3.3.2. Flux decline study for the dye filtration process In this paper, Titan Yellow dye solution was also used to evaluate the antifouling property of the prepared membranes with entrapped NaA particles and batch constant volume filtration process was studied. Titan Yellow dye with molecular weight about 700 was a kind of disperse dye. So it can be rejected by UF membrane with MWCO 10,000 because of the association effect of
the dye. At the same time, it is a good choice for demonstrating the antifouling performance of the membranes for its hydrophobic characteristics. According to Fig. 7, it was found that N4 showed better antifouling performance compared with N1. It can be interpreted that the improvement of membrane hydrophilicity increased the dye/water interfacial tension and decreased the adsorption between dye and membrane. So in the first 0.5 h, it was found that the flux of N1 decreased from 172 to 67 L/m2 h while the flux of N4 decreased from 183 to 106 L/m2 h which indicated that N4 had excellent antifouling property. Then in the subsequent 1 h test, the two membranes showed similar performance. This might be caused by that N4 (Rdye = 92%) had better Titan Yellow dye
Fig. 10. Effect of polymer concentration on the cross-section morphology of the membranes.
R. Han et al. / Journal of Membrane Science 345 (2009) 5–12
rejection in comparison with N1 (Rdye = 81%). The retained solutes may accumulate at the membrane surface which caused serious concentration polarization and greatly decreased the flux of N4. 3.4. Thermal analysis Thermal analysis (DSC) was performed on the N1 and N4 to investigate the interaction between PPESK and the NaA particles. Each sample was analyzed in the 100/400 ◦ C temperature range with scan rate of 10 ◦ C/min. The sample was heated from 20 to 400 ◦ C, then was cooled down to 100 ◦ C and then heated again to 400 ◦ C. The analysis of the second heating step was carried out. The DSC analysis of the studied N1and N4 in Fig. 8 indicated that the addition of NaA particles has no effect on the Tg (about 280 ◦ C) of the PPESK material which demonstrated that they are immiscible. This may be caused by that the NaA particles have strong hydrophilicity while the PPESK material is hydrophobic. This phenomenon was also can be demonstrated with the SEM image of the membrane. 3.5. Effect of polymer concentration on the performance of PPESK UF membrane When its rejection is about 90%, the PEG’s molecular weight was considered as MWCO of the membrane. NaA particles content was fixed 3 wt.% for further study because N4 membrane showed good hydrophilicity and NaA particles can be well dispersed below 4 wt.%. In order to prepare UF membranes with different rejection to adapt different application conditions, the amount of PPESK varied from 12 to 18 by weight of the suspension and these samples were labeled from N7 to N13 as listed in Table 3. According to Fig. 9, rejection of PEG 10,000 was raised from 78.5 to 100% and PEG 6000 rejection was raised from 60.4 to 97.2%. MWCO of N9 was considered to be 10,000 because its rejection for PEG 10,000 was 92%. At the same time, MWCO of N10 was considered to be 6000. PEG 2000 was also tested on N11–N13. It showed that N13 had a MWCO 2000 but it still had high flux 132 L/m2 h at 0.1 MPa because the hydrophilicity of NaA zeolite particles. When the NaA content was fixed 3 wt.%, UF experiments indicated that PPESK UF membranes with different MWCO (MWCO 10,000, MWCO 6000 and MWCO 2000) were fabricated with better pure water flux (from 402 to 132 L/m2 h at 0.1 MPa) when compared with commercial UF membrane according to Table 4 [28]. Higher polymer concentration in the casting solution usually resulted in a higher polymer concentration at the membrane top surface and slowed the exchange speed between solvent and water which in favor of delayed demixing. As the increase of the delay time, the distance between the film/bath interface in the film also increases, so the first formed nuclei of the dilute phase are formed at a great distance in the film from the film/bath interface. Thus the thickness of dense top layer increases with increasing polymer concentration [29]. There was a significant morphology variation in the cross-section of the membranes with the increase of PPESK concentration in the casting suspension with NaA particles which could be observed from Fig. 10. The finger-like pore numbers decreased and the macrovoids in the sublayer were suppressed while the Table 4 Performance comparison between our composite UF membranes and commercial GE UF membrane (at 0.1 MPa, 25 ◦ C). MWCO N9 N10 N13 GE P series GE G series
10,000 6,000 2,000 10,000 8,000
Flux (L/m2 h) 402 246 132 169 6
11
skin layer became thicker. If the concentration was increased further, the viscosity of the casting suspension was found too high to prepare membrane easily. It is ready to yield a higher solute rejection rate and lower flux with raised polymer concentration according to Fig. 9. The polymer content of the casting suspension exerted the most obvious influence: size and number of pores decreased as the polymer concentration was raised and consequently, the flux became smaller and tinier molecules were retained. 4. Conclusions In the present study, PPESK UF membrane was modified by uniformly dispersing inorganic NaA zeolite particles in the PPESK casting suspension. The membranes were fabricated by the traditional phase inversion technique. The membrane morphologies and structure analysis using SEM indicates that the addition of NaA particles contributes the membranes with a denser skin layer and bigger macrovoids in the sublayer. The membrane hydrophilicity was enhanced due to the introduction of hydrophilic NaA particles. Permeability and rejection experiments showed that the PEG 6000 rejection of the membranes were remarkably elevated from 77.9 to 96.8% while the flux decreased slightly from 340 to 246 L/m2 h when hydrophilic NaA particles were added. After the NaA content was raised to 4%, NaA agglomerates were observed in the micrographs of the cross-section and surface of PPESK UF membrane. Antifouling performance was studied with BSA solution and Titan Yellow dye solution. Both of them indicated N4 with NaA addition had better fouling resistance than N1. Thermal analysis (DSC) on the membranes N1 and N4 indicated that the addition of NaA particles did not decline the Tg of the composite material. At last, PPESK UF membranes with different polymer content were prepared while the NaA content was fixed 3 wt.%. UF experiments indicated that PPESK UF membranes with different MWCO (MWCO 10,000, MWCO 6000 and MWCO 2000) were fabricated with excellent pure water flux (>132 L/m2 h at 0.1 MPa). Hydrophilic NaA zeolite had strong impact on the phase demixing of the casting suspension because it can absorb water vapor in the air and caused dense membrane skin layer in the nascent membrane. Then the NaA particles in the membrane will absorb water and increase the rate of water flowing into the membrane which caused instantaneous liquid–liquid demixing when the it was immersed in the coagulation bath. So at last the composite membranes showed higher rejections and finger-like pores in the cross-section of the membranes. Acknowledgements The authors gratefully acknowledge Ph.D. Wei Xiao for providing NaA zeolite particles and the financial support of the National Basic Research Program of China (“973” No. 2003CB615700). References [1] X.G. Jian, Y. Dai, L. Zeng, R.X. Xu, Application of poly (phthalazinone ether sulfone ketone)s to gas membrane separation, J. Appl. Polym. Sci. 71 (1999) 2385–2390. [2] X.G. Jian, Y. Dai, G.H. He, G.H. Chen, Preparation of UF and NF poly (phthalazine ether sulfone ketone) membranes for high temperature application, J. Membr. Sci. 161 (1999) 185–191. [3] Y.Q. Yang, X.G. Jian, D.L. Yang, S.H. Zhang, L.J. Zou, Poly (phthalazinone ether sulfone ketone) (PPESK) hollow fiber asymmetric nanofiltration membranes: preparation, morphologies and properties, J. Membr. Sci. 270 (2006) 1–12. [4] Y.Q. Yang, D.L. Yang, S.H. Zhang, J. Wang, X.G. Jian, Preparation and characterization of poly (phthalazinone ether sulfone ketone) hollow fiber ultrafiltration membranes with excellent thermal stability, J. Membr. Sci. 280 (2006) 957–968. [5] Y. Dai, X.G. Jian, X.M. Liu, M.D. Guiver, Synthesis and characterization of sulfonated poly (phthalazinone ether sulfone ketone) for ultrafiltration and nanofiltration membranes, J. Appl. Polym. Sci. 79 (2001) 1685–1692.
12
R. Han et al. / Journal of Membrane Science 345 (2009) 5–12
[6] S.H. Zhang, X.G. Jian, Y. Dai, Preparation of sulfonated poly (phthalazinone ether sulfone ketone) composite nanofiltration membrane, J. Membr. Sci. 246 (2005) 121–126. [7] Y. Su, X.G. Jian, S.H. Zhang, G.Q. Wang, Preparation and characterization of quaternized poly (phthalazinone ether sulfone ketone) NF membranes, J. Membr. Sci. 241 (2004) 225–233. [8] L.P. Zhu, L. Xu, B.K. Zhu, Y.X. Feng, Y.Y. Xu, Preparation and characterization of improved fouling-resistant PPESK ultrafiltration membranes with amphiphilic PPESK-graft-PEG copolymers as additives, J. Membr. Sci. 294 (2007) 196–206. [9] Z. Jin, D.L. Yang, S.H. Zhang, X.G. Jian, Preparation and characterization of poly (phthalazinone ether sulfone ketone) hollow fiber ultrafiltration membrane with high-molecular weight cut-off, J. Membr. Sci. 306 (2007) 253–260. [10] S. Kiminori, N. Takashi, A high reproducible fabrication method for industrial: production of high flux NaA zeolite membrane, J. Membr. Sci. 301 (2007) 151–161. [11] A. Bottino, G. Capannelli, V. D’Asti, P. Piaggio, Preparation and properties of novel organic–inorganic porous membranes, Sep. Purif. Technol. 22–23 (2001) 269–275. [12] A. Bottino, G. Capannelli, A. Comite, Preparation and characterization of novel porous PVDF-ZrO2 composite membranes, Desalination 146 (2002) 35–40. [13] Y. Lu, S.L. Yu, B.X. Chai, X.D. Shun, Effect of nano-sized Al2 O3 -particle addition on PVDF ultrafiltration membrane performance, J. Membr. Sci. 276 (2006) 162–167. [14] Y.N. Yang, H.X. Zhang, P. Wang, Q. Zheng, J. Li, The influence of nano-sized TiO2 fillers on the morphologies and properties of PSF UF membrane, J. Membr. Sci. 288 (2007) 231–238. [15] X. Cao, J. Ma, X.H. Shi, Z.J. Ren, Effect of TiO2 nanoparticle size on the performance of PVDF membrane, Appl. Surf. Sci. 253 (2006) 2003–2010. [16] Z.Q. Huang, K. Chen, S.N. Li, X.T. Yin, Z. Zhang, H.T. Xu, Effect of ferrosoferric oxide content on the performances of polysulfone–ferrosoferric oxide ultrafiltration membranes, J. Membr. Sci. 315 (2008) 164–171.
[17] J.S. Taurozzi, H. Arul, V.Z. Bosak, A.F. Burban, T.C. Voice, M.L. Bruening, V.V. Tarabara, Effect of filler incorporation route on the properties of polysulfonesilver nanocomposite membranes of different porosities, J. Membr. Sci. 325 (2008) 58–68. [18] Y.Q. Zhang, L.B. Shan, Z.Y. Tu, Y.H. Zhang, Preparation and characterization of novel Ce-doped nonstoichiometric nanosilica/polysulfone composite membranes, Sep. Purif. Technol. 63 (2008) 207–212. [19] J.B. Li, J.W. Zhu, M.S. Zheng, Morphologies and properties of poly (phthalazinone ether sulfone ketone) matrix ultrafiltration membranes with entrapped TiO2 nanoparticles, J. Appl. Polym. Sci. 103 (2007) 3623–3629. [20] A. Urtiaga, E.D. Gorri, C. Casado, I. Ortiz, Pervaporative dehydration of industrial solvents using a zeolite NaA commercial membrane, Sep. Purif. Technol. 32 (2003) 207–213. [21] D. Breck, Zeolite Molecular Sieves, Wiley, New York, 1974. [22] S.M. Auerbach, K.A. Carrado, P.K. Dutta, Handbook of Zeolite Science and Technology, Marcel Dekker, Inc., 2003. [23] Z.H. Zhou, J.H. Yang, Y. Zhang, L.F. Chang, W.G. Sun, J.Q. Wang, NaA zeolite/carbon nanocomposite thin films with high permeance for CO2 /N2 separation, Sep. Purif. Technol. 55 (2007) 392–395. [24] H.C. Parka, Y.P. Kimb, H.Y. Kimb, Y.S. Kanga, Membrane formation by water vapor induced phase inversion, J. Membr. Sci. 156 (1999) 169–178. [25] P.Y. Qin, C.X. Chen, B.B. Han, S. Takuji, J.D. Li, B.H. Sun, Preparation of poly (phthalazinone ether sulfone ketone) asymmetric ultrafiltration membrane. II. The gelation process, J. Membr. Sci. 268 (2006) 181–188. [26] N. Maximous, G. Nakhla, W. Wan, Comparative assessment of hydrophobic and hydrophilic membrane fouling in wastewater applications, J. Membr. Sci. 339 (2009) 93–99. [27] C. Fersi, L. Gzara, M. Dhahbi, Flux decline study for textile wastewater treatment by membrane processes, Desalination 244 (2009) 321–332. [28] Desal Pure Water Catalog, GE Infrastructure Water & Process Technologies, 2004, pp. 48–50. [29] M. Mulder, Basic Principles of Membrane Technology, Kluwer Academic publishers, 1991, pp. 102–103.
Contents lists available at ScienceDirect
Journal of Membrane Science journal homepage: www.elsevier.com/locate/memsci
Effect of NaA zeolite particle addition on poly(phthalazinone ether sulfone ketone) composite ultrafiltration (UF) membrane performance Runlin Han, Shouhai Zhang, Cheng Liu, Yutian Wang, Xigao Jian ∗ College of Chemical Engineeering, Dalian University of Technology, Dalian 116012, PR China
a r t i c l e
i n f o
Article history: Received 20 May 2009 Received in revised form 24 July 2009 Accepted 28 July 2009 Available online 12 August 2009 Keywords: Poly(phthalazinone ether sulfone ketone) NaA zeolite particles Ultrafiltration membrane Hydrophilicity
a b s t r a c t PPESK is of particular interest in the fabrication of UF membrane for its considerable mechanical strength, thermal stability and chemical resistance. However, its use in aqueous phase is restricted due to its hydrophobicity. NaA zeolite is one of most hydrophilic inorganic material with low atom ratio of Si:Al (1:1) and big channel diameter and good comprehensive performance which may have the potential to improve the properties of PPESK. Composite ultrafiltration (UF) membranes with entrapped NaA zeolite particles were prepared from poly(phthalazinone ether sulfone ketone) (PPESK). The membranes were prepared with phase inversion process and were characterized by UF experiments and scanning electron microscope (SEM) observations. At 3 wt.% NaA content, the composite membranes held excellent water permeability, hydrophilicity and good antifouling ability with enhanced retentions. Higher NaA content (than 3 wt.%) caused a particle aggregation to some extent according to the cross-section and external surface morphology. However, the excess incorporation of the zeolite particles did not cause decline of membrane performance according to the UF experiments. Antifouling performance was tested with resistance-in-series Model and flux decline in Titan Yellow dye solution. Thermal analysis (DSC) was performed in order to investigate the interactions between NaA particles and PPESK. PPESK UF membranes with different molecular weight cut-off (MWCO) and high flux were obtained by adjusting the polymer concentration. It was concluded that the membrane prepared in our laboratory had better performance than two kinds of commercial UF membranes. © 2009 Elsevier B.V. All rights reserved.
1. Introduction PPESK is one of the most attractive polymer materials for separation membranes, notable for its excellent thermal stability, extraordinary mechanical properties, high chemical resistance and good solubility [1–4]. However, it has a limited antifouling ability induced by its hydrophobic nature. Some efforts have been made to improve the hydrophilicity and separation performances of PPESK membranes. Modification of PPESK by sulfonation with concentrated or fuming sulfuric acid as sulfonation agents was carried out to prepare membrane materials with increased hydrophilicity and potentially increased fouling resistance [5]. Thin film composite (TFC) membranes were prepared from sulfonated SPPESK as a top layer coated onto PPESK UF support membranes [6]. Quaternized PPESK and amphiphilic graft copolymer consisting of PPESK backbones and PEG comb-like side chains (PPESK-gPEG) were synthesized [7,8]. High molecular weight additive like
∗ Corresponding author. Tel.: +86 411 83653426; fax: +86 411 83639223. E-mail address: [email protected] (X. Jian). 0376-7388/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.memsci.2009.07.052
poly(vinyl pyrrolidone) (PVP) was used to enhance the porosity and hydrophilic performance of the PPESK UF membrane [9]. Inorganic membranes can offer better chemical, thermal and antifouling resistance. It is unfortunate that the significant spread of commercial applications has been limited. They remain expensive and brittle, with poor separation performance and membrane forming ability compared with organic membrane [10]. In recent years, inorganic particles have attracted great attention for the modification of separation membrane. Inorganic materials that often could be blended with polyvinylidene fluoride (PVDF) and polysulfone (PSf) include silica (SiO2 ) [11], zirconium dioxide (ZrO2 ) [12], alumina (Al2 O3 ) particles [13], titanium dioxide (TiO2 ) [14,15] and other inorganic materials were also studied for special function [16–18]. PPESK UF membrane was modified by uniformly dispersing inorganic TiO2 nanoparticles in the PPESK casting solution. The comprehensive performances of the membrane were enhanced by TiO2 addition. The membrane hydrophilicity and surface wettability were enhanced due to the introduction of hydrophilic TiO2 particles. Permeability and rejection experiments showed that the pure water flux and solute rejection of the membranes were remarkably elevated when less amount of TiO2 was
6
R. Han et al. / Journal of Membrane Science 345 (2009) 5–12
Fig. 1. Chemical structure of poly(phthalazine ether sulfone ketone) (PPESK).
2. Experimental 2.1. Materials and instruments
Fig. 2. Morphology of NaA zeolite particles.
added [19]. Zeolites are microporous crystalline materials, routinely used as catalysts, ion-exchangers and absorbents because of their chemical structure. NaA zeolite was considered to be one of the most hydrophilic inorganic membrane materials and was widely used as pervaporation composite membrane material or desiccant agent [20]. NaA zeolite particles are generally stable in a range of aqueous and organic solvents, so they should not wash out rapidly [21,22]. However, there was no report about utilizing NaA zeolite particles to improve antifouling ability of PPESK and other UF membrane materials. So PPESK matrix UF membranes with entrapped NaA particles were prepared to enhance the performance of PPESK UF membrane. The effects of the NaA addition on the membrane morphologies and performances were investigated by SEM, UF experiments and antifouling test.
PPESK (sulfone:ketone = 1:1, [] = 0.56 dL/g) was provided by Dalian New Polymer Co. (PR China) and its chemical structure was showed in Fig. 1. N,N-Dimethylacetamide (DMAc) and polyethyleneglycol (PEG 10,000, PEG 6000 and PEG 2000) were analytical grade and used as received. NaA zeolite particles were provided by Ph.D. Wei Xiao (Inorganic membrane laboratory, Dalian university of technology). Synthesis method of NaA zeolite particles was followed as Ref. [23] and it was characterized with SEM (JSM-5600L, JEOL, Japan) and X-ray diffraction (XRD) with a Philips Analytical X-ray diffractometer using Cu K␣ radiation under 40 kV and 100 mA. The interaction was analyzed with DSC (DSC822, METTLER TOLEDO, Switzerland). The membrane feed solution side was stirred magnetically to reduce concentration polarization. A flat-sheet dead-end membrane cell (Ecological Environment Center of Chinese Academy of Science) having an effective separation area of 41 cm2 and a feed volume of 500 mL was used in all membrane flux characterization and separation experiments. Spectrophotometer 752 PC (Shanghai Spectrum Instrument Co., Ltd., Shanghai, China) was employed for measuring the concentration of PEG and Titan Yellow dye. 2.2. Membrane preparation NaA zeolite particles after being dried 2 h at 120 ◦ C were added to the casting suspension. The amount of NaA varied as 0, 1, 2, 3, 4 and 5 wt.% by weight of the casting suspension while PPESK was fixed 15 wt.%. Then these samples were labeled as N1, N2, N3, N4, N5 and N6, respectively. The membranes were cast on a horizontal glass plate with a glass blade to make it about 200 m thick. After evaporation 10 s in the air, the membranes were precipitated by immersing them in a water bath at 6–8 ◦ C. The membranes have to be rinsed with deionized water before use. The influence to the membrane performance and morphology were studied by adjusting the NaA content and PPESK concentration. 2.3. Membrane characterization The membranes were characterized in the dead-end membrane module after they were pretreated under the pressure of 0.2 MPa for 30 min. The pure water flux and the rejection of PEG and Titan Yellow dye from its 100 mg/L solution were measured under the pressure of 0.1 MPa at ambient temperature. The permeation flux, J, is calculated as follows: J=
Fig. 3. XRD patterns of NaA zeolite.
W At
(1)
where W is the total weight of the water or solution permeated during the experiment; A is the membrane area; and t is the operation time. Rejection, R, is calculated using the following
R. Han et al. / Journal of Membrane Science 345 (2009) 5–12
7
Table 1 Composition of membranes from N1 to N6. Membrane
N1
N2
N3
N4
N5
N6
PPESK (wt.%) NaA (wt.%) DMAc (wt.%)
15 0 85
15 1 84
15 2 83
15 3 82
15 4 81
15 5 80
2.4. Membrane morphology The morphologies of the cross-section and external surface of asymmetric membranes were observed with a SEM. The samples were fractured in liquid nitrogen and sputtered with gold after they were immersed with ethanol and hexane to observe the structure of the membranes. Fig. 4. Effect of NaA content on the performance of PPESK UF membrane.
2.5. Membrane fouling evaluation equation:
R=
Cp 1− Cf
%
(2)
where Cp and Cf are the concentration of the permeate solution and the feed solution, respectively. All the experiments on flux and rejection were repeated for three times. The Relation Standard Deviation of the data was lower than 15%.
The degree of membrane fouling was calculated quantitatively using the resistance-in-series model [26,27]: J=
TMP Rt
(3)
where J is the flux (L/m2 h); TMP the transmembrane pressure (0.35 MPa); and the viscosity of solution at room
Fig. 5. Effect of NaA content on the external surface morphology of PPESK UF membranes.
8
R. Han et al. / Journal of Membrane Science 345 (2009) 5–12
temperature. Rt = Rm + Rf + Rc
(4)
A modification to this model had been applied in this research to differentiate between pore plugging, chemically reversible (i.e. cake layer removed by NaOCl backwash) and readily reversible (i.e. cake layer removed by cross-flow washing with DIW) cake resistances as follows: Rf = Ric + Rp
(5)
where Rm is the intrinsic membrane resistance; Rf is the sum of the resistances caused by solute adsorption into the membrane pores or walls and chemically reversible cake. Rc is the cake resistance formed by cake layer deposited over the membrane surface. Ric is the resistance due to chemically reversible cake and Rp is the resistance due to pore plugging. Resistance values can be obtained through the following equations: Rm =
Rf = Rp =
DI water · Jiw
DI water · Jiw
TMP − (Rm + Rp + Ric ) BSA · J
Jiw , Jfw , JBW and J are flux values determined experimentally. Jiw is the initial deionized water flux before ultrafiltration, Jfw is final deionized water flux after removing cake layer by cross-flow washing, JBW is the deionized water flux after removing chemically reversible cake layer by backwash with 100 ppm NaOCl, and J is flux with bovine serum albumin (BSA) (a 1 g/L bovine serum albumin solution in phosphate buffered saline (PBS) at 20 ◦ C and at pH 7.4). Filtration and washing time were all controlled 10 min in this work. Flux decline study for the dye filtration process was also studied with the Titan Yellow dye solution to evaluate the antifouling property of the prepared membranes with entrapped NaA particles. 3. Results and discussions 3.1. Characterization of NaA zeolite particles
TMP
TMP
Rc =
− Rm
TMP − Rm DI water · JBW
It can be seen from Fig. 2 that all NaA particles with the mean diameter of 2 m are essentially symmetrical. The XRD patterns of the synthesized NaA zeolite in Fig. 3 are compared with standard NaA zeolite crystals and the pick and relative intensities are very compatible with the standard pattern. So they both confirmed that the particles utilized in this work were pure NaA zeolite.
Fig. 6. Effect of NaA content on the cross-section morphology of PPESK UF membranes.
R. Han et al. / Journal of Membrane Science 345 (2009) 5–12 Table 2 Filtration resistances of the N1 and N4 membranes.
N1 N4
Rm /Rt (%)
Rf /Rt (%)
Rc /Rt (%)
Rc /Rf (%)
21 31
67 52
12 17
18 33
Fig. 7. Antifouling performance of N1 and N4 (tested with Titan Yellow dye).
9
adsorbed water vapor in the air. So in the evaporation stage delayed liquid–liquid demixing occurred in the nascent membrane surface which caused a more dense skin layer formed [24]. The reasons for the decrease of pure water flux and the increase of rejection were that the performance of membranes was controlled by the overall porosity and the pore size in the external surface. When the membrane top surfaces were magnified at 2000 times in Fig. 5, it can be observed that the external surfaces of the membrane became tough. The cross-section displayed obvious finger-like pores and the skin layer became thin when NaA zeolite particles were added according to Fig. 6. It is clear that on increasing NaA concentration, the fingerlike structure becomes narrow and its number also decreases. At the same time, its asymmetric structure became more obvious with macrovoids in the sublayer. This may be induced by that NaA particles were very hydrophilic. As soon as the membrane immersed into water, NaA would strongly adsorb water which caused instantaneous liquid–liquid demixing. So it yielded a dense top layer and lower flux which could be demonstrated in Fig. 4. This phenomenon was similar with the results of PEG 1000 is a hydrated compound with high hydrophilicity, and it can enhance the hydrophilicity of the PPESK casting solution. Thus, the gelation rate increases with the increased concentration of PEG 1000 [25]. However, the flux of N6 decreased only 28% compared with N1 because of the super hydrophilicity of NaA particles. Furthermore, water can permeate through the hydrophilic and microporous NaA particles while PEG cannot. So the composite membranes showed elevated rejection and comparatively high flux. When NaA content was raised to 4 wt.%, NaA agglomerates were observed in the micrographs of the cross-section and surface of PPESK UF membrane which could be observed in Fig. 5. But it did not indicate the performance deterioration of the membranes according to Fig. 4. In fact, NaA content had been raised to 6 wt.%, however the membrane performance was quickly deteriorated with much flaw which might be caused by the strong agglomerates. 3.3. Antifouling performance comparison of N1 and N4
Fig. 8. DSC analysis of N1 and N4.
3.2. Effect of NaA content on the performance of PPESK UF membrane The polymer content was fixed on 15 wt.% and the effect of NaA content on membrane performance and morphology was studied by varying the NaA content. The composition of the membrane was listed in Table 1. As could be seen in Fig. 4, the PEG 6000 rejection increased from 77.1 to 96.8% and the pure water flux decreased slightly from 340 to 246 L/m2 h when NaA content in the casting suspension changed from 0 to 5 wt.%. This implied that the membrane surface became more dense which caused higher rejection and lower flux. It was often believed that additives like PVP, PEG and LiCl did not increase the rejection of the UF membrane. But in this work, NaA zeolite was used as additive which strongly
3.3.1. Resistance study in the filtration Based on the resistance-in-series model, the total resistance is the sum of the intrinsic membrane, cake layer and solute adsorption into the membrane pores and walls resistances. A modification of this model has been applied in this research to account for the readily reversible cake (Rrc ), chemically reversible cake (Ric ) and pore plugging (Rp ) resistances. Table 2 shows the resistance percentage value of BSA filtrations by membranes N1 and N4. The percentage contribution of cake layer resistance to the total resistance was 12 and 17% and percentage contribution of solute adsorption to the total resistance was 67 and 52% for N1 and N4, respectively. So the
Table 3 Composition of membranes from N7 to N13. Membrane
N7
N8
N9
N10
N11
N12
N13
PPESK (wt.%) NaA (wt.%) DMAc (wt.%)
12 3 85
13 3 84
14 3 83
15 3 82
16 3 81
17 3 80
18 3 79
Fig. 9. Effect of polymer concentration on the performance of the membranes.
10
R. Han et al. / Journal of Membrane Science 345 (2009) 5–12
higher value of Rc /Rf of N4 according the modified resistance-inseries model showed that N4 had better hydrophilicity than N1. The hydrophilic NaA particles in the membrane surface and membrane pores can account for the conclusion. 3.3.2. Flux decline study for the dye filtration process In this paper, Titan Yellow dye solution was also used to evaluate the antifouling property of the prepared membranes with entrapped NaA particles and batch constant volume filtration process was studied. Titan Yellow dye with molecular weight about 700 was a kind of disperse dye. So it can be rejected by UF membrane with MWCO 10,000 because of the association effect of
the dye. At the same time, it is a good choice for demonstrating the antifouling performance of the membranes for its hydrophobic characteristics. According to Fig. 7, it was found that N4 showed better antifouling performance compared with N1. It can be interpreted that the improvement of membrane hydrophilicity increased the dye/water interfacial tension and decreased the adsorption between dye and membrane. So in the first 0.5 h, it was found that the flux of N1 decreased from 172 to 67 L/m2 h while the flux of N4 decreased from 183 to 106 L/m2 h which indicated that N4 had excellent antifouling property. Then in the subsequent 1 h test, the two membranes showed similar performance. This might be caused by that N4 (Rdye = 92%) had better Titan Yellow dye
Fig. 10. Effect of polymer concentration on the cross-section morphology of the membranes.
R. Han et al. / Journal of Membrane Science 345 (2009) 5–12
rejection in comparison with N1 (Rdye = 81%). The retained solutes may accumulate at the membrane surface which caused serious concentration polarization and greatly decreased the flux of N4. 3.4. Thermal analysis Thermal analysis (DSC) was performed on the N1 and N4 to investigate the interaction between PPESK and the NaA particles. Each sample was analyzed in the 100/400 ◦ C temperature range with scan rate of 10 ◦ C/min. The sample was heated from 20 to 400 ◦ C, then was cooled down to 100 ◦ C and then heated again to 400 ◦ C. The analysis of the second heating step was carried out. The DSC analysis of the studied N1and N4 in Fig. 8 indicated that the addition of NaA particles has no effect on the Tg (about 280 ◦ C) of the PPESK material which demonstrated that they are immiscible. This may be caused by that the NaA particles have strong hydrophilicity while the PPESK material is hydrophobic. This phenomenon was also can be demonstrated with the SEM image of the membrane. 3.5. Effect of polymer concentration on the performance of PPESK UF membrane When its rejection is about 90%, the PEG’s molecular weight was considered as MWCO of the membrane. NaA particles content was fixed 3 wt.% for further study because N4 membrane showed good hydrophilicity and NaA particles can be well dispersed below 4 wt.%. In order to prepare UF membranes with different rejection to adapt different application conditions, the amount of PPESK varied from 12 to 18 by weight of the suspension and these samples were labeled from N7 to N13 as listed in Table 3. According to Fig. 9, rejection of PEG 10,000 was raised from 78.5 to 100% and PEG 6000 rejection was raised from 60.4 to 97.2%. MWCO of N9 was considered to be 10,000 because its rejection for PEG 10,000 was 92%. At the same time, MWCO of N10 was considered to be 6000. PEG 2000 was also tested on N11–N13. It showed that N13 had a MWCO 2000 but it still had high flux 132 L/m2 h at 0.1 MPa because the hydrophilicity of NaA zeolite particles. When the NaA content was fixed 3 wt.%, UF experiments indicated that PPESK UF membranes with different MWCO (MWCO 10,000, MWCO 6000 and MWCO 2000) were fabricated with better pure water flux (from 402 to 132 L/m2 h at 0.1 MPa) when compared with commercial UF membrane according to Table 4 [28]. Higher polymer concentration in the casting solution usually resulted in a higher polymer concentration at the membrane top surface and slowed the exchange speed between solvent and water which in favor of delayed demixing. As the increase of the delay time, the distance between the film/bath interface in the film also increases, so the first formed nuclei of the dilute phase are formed at a great distance in the film from the film/bath interface. Thus the thickness of dense top layer increases with increasing polymer concentration [29]. There was a significant morphology variation in the cross-section of the membranes with the increase of PPESK concentration in the casting suspension with NaA particles which could be observed from Fig. 10. The finger-like pore numbers decreased and the macrovoids in the sublayer were suppressed while the Table 4 Performance comparison between our composite UF membranes and commercial GE UF membrane (at 0.1 MPa, 25 ◦ C). MWCO N9 N10 N13 GE P series GE G series
10,000 6,000 2,000 10,000 8,000
Flux (L/m2 h) 402 246 132 169 6
11
skin layer became thicker. If the concentration was increased further, the viscosity of the casting suspension was found too high to prepare membrane easily. It is ready to yield a higher solute rejection rate and lower flux with raised polymer concentration according to Fig. 9. The polymer content of the casting suspension exerted the most obvious influence: size and number of pores decreased as the polymer concentration was raised and consequently, the flux became smaller and tinier molecules were retained. 4. Conclusions In the present study, PPESK UF membrane was modified by uniformly dispersing inorganic NaA zeolite particles in the PPESK casting suspension. The membranes were fabricated by the traditional phase inversion technique. The membrane morphologies and structure analysis using SEM indicates that the addition of NaA particles contributes the membranes with a denser skin layer and bigger macrovoids in the sublayer. The membrane hydrophilicity was enhanced due to the introduction of hydrophilic NaA particles. Permeability and rejection experiments showed that the PEG 6000 rejection of the membranes were remarkably elevated from 77.9 to 96.8% while the flux decreased slightly from 340 to 246 L/m2 h when hydrophilic NaA particles were added. After the NaA content was raised to 4%, NaA agglomerates were observed in the micrographs of the cross-section and surface of PPESK UF membrane. Antifouling performance was studied with BSA solution and Titan Yellow dye solution. Both of them indicated N4 with NaA addition had better fouling resistance than N1. Thermal analysis (DSC) on the membranes N1 and N4 indicated that the addition of NaA particles did not decline the Tg of the composite material. At last, PPESK UF membranes with different polymer content were prepared while the NaA content was fixed 3 wt.%. UF experiments indicated that PPESK UF membranes with different MWCO (MWCO 10,000, MWCO 6000 and MWCO 2000) were fabricated with excellent pure water flux (>132 L/m2 h at 0.1 MPa). Hydrophilic NaA zeolite had strong impact on the phase demixing of the casting suspension because it can absorb water vapor in the air and caused dense membrane skin layer in the nascent membrane. Then the NaA particles in the membrane will absorb water and increase the rate of water flowing into the membrane which caused instantaneous liquid–liquid demixing when the it was immersed in the coagulation bath. So at last the composite membranes showed higher rejections and finger-like pores in the cross-section of the membranes. Acknowledgements The authors gratefully acknowledge Ph.D. Wei Xiao for providing NaA zeolite particles and the financial support of the National Basic Research Program of China (“973” No. 2003CB615700). References [1] X.G. Jian, Y. Dai, L. Zeng, R.X. Xu, Application of poly (phthalazinone ether sulfone ketone)s to gas membrane separation, J. Appl. Polym. Sci. 71 (1999) 2385–2390. [2] X.G. Jian, Y. Dai, G.H. He, G.H. Chen, Preparation of UF and NF poly (phthalazine ether sulfone ketone) membranes for high temperature application, J. Membr. Sci. 161 (1999) 185–191. [3] Y.Q. Yang, X.G. Jian, D.L. Yang, S.H. Zhang, L.J. Zou, Poly (phthalazinone ether sulfone ketone) (PPESK) hollow fiber asymmetric nanofiltration membranes: preparation, morphologies and properties, J. Membr. Sci. 270 (2006) 1–12. [4] Y.Q. Yang, D.L. Yang, S.H. Zhang, J. Wang, X.G. Jian, Preparation and characterization of poly (phthalazinone ether sulfone ketone) hollow fiber ultrafiltration membranes with excellent thermal stability, J. Membr. Sci. 280 (2006) 957–968. [5] Y. Dai, X.G. Jian, X.M. Liu, M.D. Guiver, Synthesis and characterization of sulfonated poly (phthalazinone ether sulfone ketone) for ultrafiltration and nanofiltration membranes, J. Appl. Polym. Sci. 79 (2001) 1685–1692.
12
R. Han et al. / Journal of Membrane Science 345 (2009) 5–12
[6] S.H. Zhang, X.G. Jian, Y. Dai, Preparation of sulfonated poly (phthalazinone ether sulfone ketone) composite nanofiltration membrane, J. Membr. Sci. 246 (2005) 121–126. [7] Y. Su, X.G. Jian, S.H. Zhang, G.Q. Wang, Preparation and characterization of quaternized poly (phthalazinone ether sulfone ketone) NF membranes, J. Membr. Sci. 241 (2004) 225–233. [8] L.P. Zhu, L. Xu, B.K. Zhu, Y.X. Feng, Y.Y. Xu, Preparation and characterization of improved fouling-resistant PPESK ultrafiltration membranes with amphiphilic PPESK-graft-PEG copolymers as additives, J. Membr. Sci. 294 (2007) 196–206. [9] Z. Jin, D.L. Yang, S.H. Zhang, X.G. Jian, Preparation and characterization of poly (phthalazinone ether sulfone ketone) hollow fiber ultrafiltration membrane with high-molecular weight cut-off, J. Membr. Sci. 306 (2007) 253–260. [10] S. Kiminori, N. Takashi, A high reproducible fabrication method for industrial: production of high flux NaA zeolite membrane, J. Membr. Sci. 301 (2007) 151–161. [11] A. Bottino, G. Capannelli, V. D’Asti, P. Piaggio, Preparation and properties of novel organic–inorganic porous membranes, Sep. Purif. Technol. 22–23 (2001) 269–275. [12] A. Bottino, G. Capannelli, A. Comite, Preparation and characterization of novel porous PVDF-ZrO2 composite membranes, Desalination 146 (2002) 35–40. [13] Y. Lu, S.L. Yu, B.X. Chai, X.D. Shun, Effect of nano-sized Al2 O3 -particle addition on PVDF ultrafiltration membrane performance, J. Membr. Sci. 276 (2006) 162–167. [14] Y.N. Yang, H.X. Zhang, P. Wang, Q. Zheng, J. Li, The influence of nano-sized TiO2 fillers on the morphologies and properties of PSF UF membrane, J. Membr. Sci. 288 (2007) 231–238. [15] X. Cao, J. Ma, X.H. Shi, Z.J. Ren, Effect of TiO2 nanoparticle size on the performance of PVDF membrane, Appl. Surf. Sci. 253 (2006) 2003–2010. [16] Z.Q. Huang, K. Chen, S.N. Li, X.T. Yin, Z. Zhang, H.T. Xu, Effect of ferrosoferric oxide content on the performances of polysulfone–ferrosoferric oxide ultrafiltration membranes, J. Membr. Sci. 315 (2008) 164–171.
[17] J.S. Taurozzi, H. Arul, V.Z. Bosak, A.F. Burban, T.C. Voice, M.L. Bruening, V.V. Tarabara, Effect of filler incorporation route on the properties of polysulfonesilver nanocomposite membranes of different porosities, J. Membr. Sci. 325 (2008) 58–68. [18] Y.Q. Zhang, L.B. Shan, Z.Y. Tu, Y.H. Zhang, Preparation and characterization of novel Ce-doped nonstoichiometric nanosilica/polysulfone composite membranes, Sep. Purif. Technol. 63 (2008) 207–212. [19] J.B. Li, J.W. Zhu, M.S. Zheng, Morphologies and properties of poly (phthalazinone ether sulfone ketone) matrix ultrafiltration membranes with entrapped TiO2 nanoparticles, J. Appl. Polym. Sci. 103 (2007) 3623–3629. [20] A. Urtiaga, E.D. Gorri, C. Casado, I. Ortiz, Pervaporative dehydration of industrial solvents using a zeolite NaA commercial membrane, Sep. Purif. Technol. 32 (2003) 207–213. [21] D. Breck, Zeolite Molecular Sieves, Wiley, New York, 1974. [22] S.M. Auerbach, K.A. Carrado, P.K. Dutta, Handbook of Zeolite Science and Technology, Marcel Dekker, Inc., 2003. [23] Z.H. Zhou, J.H. Yang, Y. Zhang, L.F. Chang, W.G. Sun, J.Q. Wang, NaA zeolite/carbon nanocomposite thin films with high permeance for CO2 /N2 separation, Sep. Purif. Technol. 55 (2007) 392–395. [24] H.C. Parka, Y.P. Kimb, H.Y. Kimb, Y.S. Kanga, Membrane formation by water vapor induced phase inversion, J. Membr. Sci. 156 (1999) 169–178. [25] P.Y. Qin, C.X. Chen, B.B. Han, S. Takuji, J.D. Li, B.H. Sun, Preparation of poly (phthalazinone ether sulfone ketone) asymmetric ultrafiltration membrane. II. The gelation process, J. Membr. Sci. 268 (2006) 181–188. [26] N. Maximous, G. Nakhla, W. Wan, Comparative assessment of hydrophobic and hydrophilic membrane fouling in wastewater applications, J. Membr. Sci. 339 (2009) 93–99. [27] C. Fersi, L. Gzara, M. Dhahbi, Flux decline study for textile wastewater treatment by membrane processes, Desalination 244 (2009) 321–332. [28] Desal Pure Water Catalog, GE Infrastructure Water & Process Technologies, 2004, pp. 48–50. [29] M. Mulder, Basic Principles of Membrane Technology, Kluwer Academic publishers, 1991, pp. 102–103.