Fabrication of hydrophobic fluorinated silica-polyamide thin film nanocomposite reverse osmosis membranes with dramatically improved salt rejection

Accepted Manuscript Fabrication of hydrophobic fluorinated silica-polyamide thin film nanocomposite reverse osmosis membranes with dramatically improved salt rejection Ruizhi Pang, Kaisong Zhang PII: DOI: Reference:

S0021-9797(17)31094-9 http://dx.doi.org/10.1016/j.jcis.2017.09.062 YJCIS 22814

To appear in:

Journal of Colloid and Interface Science

Received Date: Revised Date: Accepted Date:

8 June 2017 9 September 2017 14 September 2017

Please cite this article as: R. Pang, K. Zhang, Fabrication of hydrophobic fluorinated silica-polyamide thin film nanocomposite reverse osmosis membranes with dramatically improved salt rejection, Journal of Colloid and Interface Science (2017), doi: http://dx.doi.org/10.1016/j.jcis.2017.09.062

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Fabrication of hydrophobic fluorinated silica-polyamide thin film nanocomposite reverse osmosis membranes with dramatically improved salt rejection Ruizhi Pang * , Kaisong Zhang * Key Laboratory of Urban Pollutant Conversion, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China ABSTRACT Thin film nanocomposite reverse osmosis (TFN RO) membranes incorporated with hydrophilic nanoparticles show a potential problem that the salt rejection can not be improved significantly. In this study, novel TFN RO membranes incorporated with hydrophobic fluorinated silica nanoparticles were fabricated to improve the salt rejection. Fluorinated silica nanoparticles were well dispersed in organic phase during the interfacial polymerization (IP) process. The TFN RO membranes were characterized with attenuated total reflectance infra-red, field emission scanning electron microscopy, atomic force microscopy and water contact angle measurements. The preparation conditions of TFN RO membranes, including IP reaction time, organic solvent removal time, and fluorinated silica loading, were optimized by characterizing desalination performance using 2000 ppm NaCl aqueous solution at 1.55 MPa and 25 oC. The salt rejection increased significantly from 96.0% without fluorinated silica nanoparticles to 98.6% with the optimal 0.12% (w/v) fluorinated silica nanoparticles, while the water flux decreased slightly from 0.99 m3/m2/day to 0.93 m3/m2/day. This study demonstrated the potential use of hydrophobic

nanoparticles in high-performance TFN RO membranes. Keywords: Thin film nanocomposite; Reverse osmosis; Hydrophobic nanoparticles; Fluorinated silica *Corresponding author. Tel/Fax: +86 592 6190534. E-mail address: [email protected] (R. Pang), [email protected] (K. Zhang). 1. Introduction With the fast growth of population, climate change and inappropriate wastewater management, the global drinking water shortage is becoming an inevitable issue [1]. Reverse osmosis (RO) desalination process has proved to be one of the most feasible strategies to this issue [2]. The widely used RO membrane in current market is the polyamide (PA) thin film composite (TFC) membrane most commonly synthesized via interfacial polymerization (IP) of m-phenylenediamine (MPD) and trimesoyl chloride (TMC) on nanoporous polysulfone supports [3, 4]. Over the last 35 years, the IP conditions and post-treatment process has been continually improved. However, It is very difficult to control the structure of the PA TFC membrane and the desalination efficiency of PA TFC membranes remains relatively low [5]. In recent years, the thin film nanocomposite (TFN) membranes has attracted attention [6]. It was demonstrated that the addition of hydrophilic nanoparticles into PA films had led to the increase of water flux [7]. Kinds of nanoparticles have been investigated to prepare TFN membranes including Ag [8], SiO2 [9, 10], TiO2 [11], Al2O3 [12], carbon nanotubes [13, 14], aluminosilicate single-walled nanotubes [15], halloysite nanotubes [16], graphene oxide [17, 18], clay nanosheets [19], NaA zeolite

[21-22], NaY zeolite [23], silicalite-1 nanozeolites [24], zeolitic imidazolate framework-8 [25], ordered mesoporous silica [26] and ordered mesoporous carbon [27]. In general, the aforementioned studies mainly focus on improving the hydrophilicity of PA membrane and enhancing the water flux. However, hydrophilic nanoparticles even at low concentration may not be uniformly dispersed in PA films [28]. The salt rejection can not be improved significantly by incorporating hydrophilic nanoparticles within PA films. It has been demonstrated that the impact of increased water permeability on the efficiency of desalination processes is limited and inadequate membrane selectivity hinders process efficacy [29]. It therefore seems interesting to fabricate TFN RO membranes with dramatically improved salt rejection. To the best of our knowledge, this is the first study to fabricate hydrophobic nanoparticle-PA TFN RO membranes with dramatically improved salt rejection. Herein, novel TFN RO membranes with dramatically improved salt rejection have been developed by incorporating hydrophobic fluorinated silica nanoparticles within PA films. The TFN RO membranes were prepared by dispersing fluorinated silica nanoparticles in organic solution during the IP process. The membrane composition and morphology were examined by attenuated total reflectance infra-red (ATR-IR), atomic force microscopy (AFM) and field emission scanning electron microscopy (FESEM). Water contact angles were measured on prepared membranes with different fluorinated silica loadings to evaluate the membrane hydrophobicity. The effects of IP reaction time, organic solvent removal time and fluorinated silica loading on brackish water desalination performance were optimized.

2. Experimental 2.1. Materials Tetraethyl

orthosilicate

(TEOS,

>96%,

TCI),

1H,1H,2H,2H-

perfluorodecyltriethoxysilane (PFTS, >98%, TCI), ammonium (25%~28% NH3·H2O, Sinopharm) and ethanol (>99.7%, Sinopharm) were used for preparing the hydrophobic fluorinated silica nanoparticles. Polysulfone (PSF, P3500L, Solvay), sodium lauryl sulfate (SLS, >97%, Sinopharm) and 1-methyl-2-pyrrolidinone (NMP,

>99%,

Sinopharm)

were

used

for

preparing

the

PSF

m-Phenylenediamine (MPD, >98%, TCI), (±)-Camphor-10-sulfonic acid

support. (CSA,

99%, Aladdin), triethylamine (TEA, >97%, Sinopharm), Trimesoyl chloride (TMC, >98%, TCI) were used as monomer to prepare the PA selective layer. Isopar G (ExxonMobil

Chemical)

was

used

as

organic

solvent.

Sodium

chloride

(NaCl, >99.5%, Sinopharm) was used to test the membrane desalination performance. 2.2. Fluorinated silica nanoparticles synthesis and characterization Fluorinated silica nanoparticles were prepared referring to previously reported procedures [30, 31]. Briefly, TEOS (20 ml) together with PFTS (mole ratio TEOS: PFTS=10: 1) were dissolved in ethanol (100ml). The solution was added dropwise to ammonium/ethanol solution (24ml ammonium in 100ml ethanol) and stirred for 12 hr. The milky mixture solution was then centrifuged at 6000 rpm for 10 min. The resulting precipitates were collected, further washed with ethanol 3 times and dried at room temperature. Morphological characterization of fluorinated silica nanoparticles was examined by FESEM (HITACHI S-4800). Fourier transform infrared (FTIR,

Nicolet iS10, Thermo Fisher Scientific) spectrometry was employed to characterize the chemical structure of the synthesized fluorinated silica nanoparticles. 2.3. Preparation of PSF support The PSF support was prepared by phase inversion induced by immersion precipitation technique according to previously reported procedures [32, 33]. Typically, a solution containing 16.5 wt% PSF, 0.3 wt% water, 0.3 wt% SLS and 82.9 wt% NMP was cast onto a polyester nonwoven fabric and immersed in a water bath immediately. The prepared PSF support was stored in NaHSO3 solution (1.5 wt%). 2.4. Preparation of TFC and TFN RO Membranes TFC RO membranes were prepared on the PSF support by IP process. The aqueous solution containing 2 wt% MPD, 5 wt% CSA–TEA salt and 93 wt% water was poured onto the PSF support and soaked for 10 s. The support was dried for about 3 min, while the droplets were absorbed by tissue papers. After that, the organic phase solution containing 0.1 wt% TMC and 99.9 wt% Isopar G was poured on the amine saturated support. The organic phase solution was poured off after 14 s of IP reaction. The membrane was then cured in the oven at 90 oC for 5 min to remove the organic solvent. Finally, the membrane was stored in deionized water before testing. The fabrication of TFN RO membranes was carried out by adding a certain amount of fluorinated silica nanoparticles in the organic phase solution, while the other conditions were identical to that of TFC membrane. The dispersion of fluorinated silica nanoparticles in the organic phase solution could be obtained by ultrasonication for 30 min.

2.5. Characterization of TFC and TFN RO Membranes The chemical structure of the membrane surface was characterized by ATR-IR (Nicolet iS10, Thermo Fisher Scientific). FESEM (as described in Section 2.2) and AFM (Agilent 5500) were used to characterize membrane surface morphologies. The contact angle goniometer (DSA 100, Krüss) was used to measure the contact angles of TFC and TFN RO membranes. The water flux and salt rejection of RO membranes were evaluated in a cross-flow stainless steel cell (Sterlitech) with an active area of 42 cm2 under brackish water desalination conditions (25 oC and 1.55 MPa). The 2000 ppm NaCl solution was used as the feed solution to simulate brackish water composition. The water flux and salt rejection were measured by at least three membrane samples and then averaged, according to the reported method in the literature [19, 23]. 3. Results and discussion 3.1. Characterization of fluorinated silica nanoparticles

200nm

Fig. 1. SEM image for the synthesized fluorinated silica nanoparticles.

Fig. 2. FTIR spectrum of fluorinated silica nanoparticles.

The hydrolysis rate of TEOS is higher than that of PFTS. The formed silica particles were covered with hydrolysed PFTS [34]. As can be seen in Fig. 1, the average nanoparticle size is around 150 nm to 200 nm. The FTIR spectrum of fluorinated silica nanoparticles are shown in Fig. 2. The peaks at 1087 and 810 cm-1 were corresponding to the Si–O–Si vibrations. Peaks at 1205 and 1150 cm-1 were observed due to C–F stretching vibrations. The FTIR spectrum confirmed the formed silica particle were covered with the hydrolysed PFTS. 3.2. Characterization of TFC/TFN RO membranes

Fig. 3. ATR-IR spectra of the TFC membrane and the TFN membrane with 0.12% (w/v) fluorinated silica in organic phase.

The ATR-IR spectra of the TFC membrane and the TFN membrane with 0.12% (w/v) fluorinated silica nanoparticles in organic phase are shown in Fig. 3. The typical amide peak was observed at 1540 cm-1 in both spectra [35]. The new peak of TFN membrane at 1087 cm-1 was assigned to the Si–O–Si groups stretching, indicating the successful incorporation of fluorinated silica nanoparticles within polyamide films. Therefore, the membrane morphology and desalination performance of obtained TFN RO membranes can be affected. The effects of fluorinated silica incorporation on membrane surface morphology were investigated by SEM and AFM. The SEM images of surface morphology are presented in Fig. 4. Compared to the TFC membrane, the typical peak-and-valley structure of polyamide morphology was smoothened by the incorporation of fluorinated silica. Moreover, fluorinated silica nanoparticles were observed on the

TFN membrane surface. The SEM images demonstrate that the fluorinated silica nanoparticles were embedded in the polyamide layer. (a)

(b)

1.0μm

1.0μm

Fig. 4. SEM images for surface morphology of (a) TFC membrane and (b) TFN membrane with 0.12% (w/v) fluorinated silica in organic phase.

(a)

Sa=89.5 ± 11.5 nm

(b)

Sa=61.9 ± 5.6 nm

Fig. 5. AFM images of (a) TFC membrane and (b) TFN membrane with 0.12% (w/v) fluorinated silica in organic phase.

The surface roughness of both TFC membrane and TFN membrane with 0.12% (w/v) fluorinated silica in organic phase was measured by AFM. As shown in Fig. 5, the mean roughness (Sa) decreased from 89.5 nm for TFC membrane to 61.9 nm for TFN membrane with 0.12% (w/v) fluorinated silica in organic phase. The AFM

results further demonstrated the peak-and-valley structure of surface morphology was smoothened by the incorporation of fluorinated silica. The surface area decreased with the decrease in roughness, thus the decrease of surface roughness could lead to the decrease of water flux.

Fig. 6. Water contact angle data of the TFC membrane and the TFN membranes with different fluorinated silica nanoparticles loading.

The water contact angle data of TFC membrane and TFN membranes with different fluorinated silica nanoparticles loading are shown in Fig. 6. The contact angle of TFC membrane without fluorinated silica nanoparticles loading is 61.7o. The contact angle of the TFN membranes increased from 66.8o to 117.7o with increasing fluorinated silica loading from 0.12% (w/v) to 0.48% (w/v). The increase in the contact angle normally indicates the increase in hydrophobicity. The increased hydrophobicity of the TFN membranes could be due to the hydrophobicity property of fluorinated silica nanoparticles. It is usually assumed that membrane fouling reduces

by the increase in surface hydrophilicity. However, it has been demonstrated that hydrophobic surface also favors fouling reduction [36]. Moreover, the increased salt rejection by surface hydrophobicity will improve the efficiency of desalination processes [29]. 3.3. Impacts of fluorinated silica nanoparticles loading on membrane desalination performance

Fig. 7. Impacts of fluorinated silica loading on membrane desalination performance (adding fluorinated silica in organic phase).

The impacts of fluorinated silica loading on water flux and salt rejection are shown in Fig. 7. The salt rejection first increased significantly and then decreased as the adding of fluorinated silica nanoparticles, while the water flux continuously decreased. The TFN RO membrane showed the best desalination performance at the 0.12% (w/v) fluorinated silica loading. The salt rejection increased significantly from 96.0% for TFC membrane to 98.6% for the TFN membrane with 0.12% fluorinated

silica loading, and the water flux decreased slightly from 0.99 m3/m2/day to 0.93 m3/m2/day. The salt rejection was achieved by measuring the electrical conductivity of permeate and feed solutions. The electrical conductivity of feed solution (2000 ppm NaCl) was 3970 μS/cm. The electrical conductivity of permeate solution was 158.8 μS/cm as the salt rejection was 96.0%. However, the electrical conductivity of permeate solution was only 55.6 μS/cm as the salt rejection was 98.6%. Therefore, the salt rejection was improved dramatically by incorporating hydrophobic fluorinated silica nanoparticles. The results indicated that the fluorinated silica nanoparticles made a great contribution to the considerable increase of the salt rejection. It was suggested that the incorporation of hydrophobic fluorinated silica not only decreased water passage by increasing membrane hydrophobicity but also decreased salt passage. The salt passage decrement is larger than water flux decrement and thus the salt rejection will be improved. However, the interstitial defects were formed at the high fluorinated silica nanoparticles concentration during the preparation of TFN RO membrane. Thus, the salt rejection decreased at the high fluorinated silica concentration. The novel TFN RO membrane was compared with the other TFN RO membranes reported in the literature. As shown in Table 1, the salt rejection decreased by incorporating functionalized multi-walled carbon nanotubes (MWNTs), porous MCM-41 nanoparticles and graphene oxide nanosheets [13, 26, 37]. However, the salt rejection was improved dramatically by incorporating hydrophobic fluorinated silica nanoparticles.

Table 1 Performance comparison of the novel TFN RO membrane with the other TFN RO membranes reported in the literature. NaCl rejection without

NaCl rejection with

NaCl rejection

nanoparticle (%)

nanoparticle (%)

change

96.0

98.6

Increased

This work

MWNTs

>95

~90

Decreased

[13]

MCM-41

98.1

97.9

Nanoparticle

References

Fluorinated silica

Decreased [26] slightly Graphene 95.7

93.8

Decreased

[37]

oxide

3.4. Impacts of IP reaction time on TFN RO membrane desalination performance

Fig. 8. Impacts of interfacial polymerization reaction time on TFN RO membrane desalination performance (adding 0.12% (w/v) fluorinated silica nanoparticles in organic phase).

Normally, a longer IP time increases the salt rejection and decreases the water flux [38]. However, a different result was observed in the preparation of TFN membranes incorporated with hydrophobic nanoparticles. As shown in Fig. 8, the water flux first decreased and then increased as the IP time increased, while the salt rejection first increased and then decreased. The water flux increase and salt rejection decrease from 14s IP time to 28s IP time could be attributed to the formed interstitial defects by the additional incorporation of fluorinated silica nanoparticles during the longer reaction period. As a result, 14 s was found to be the optimal IP time in the preparation of TFN membranes incorporated with hydrophobic nanoparticles. 3.5. Impacts of organic solvent removal time on TFN RO membrane desalination performance

Fig. 9. Impacts of organic solvent removal time on TFN RO membrane desalination performance (adding 0.12% (w/v) fluorinated silica nanoparticles in organic phase).

The effects of organic solvent removal time at 90 oC on water flux and salt

rejection are shown in Fig. 9. All the Isopar G was removed as the organic solvent removal time was around 4–5 min. The TFN membranes showed a water flux around 0.93 m3/m2/day and a salt rejection around 98.6%. When the organic solvent removal time was increased to 6 min, the salt rejection decreased to 97.7%. The decreased salt rejection might result from the shrinkage or collapse of the PSF support membrane pores due to the excessive organic solvent removal time [39, 40]. As a result, 5 min was found to be the optimal organic solvent removal time. 4. Conclusions The hydrophobic fluorinated silica nanoparticles were investigated as novel filler in TFN RO membranes. The successful incorporation of fluorinated silica nanoparticles was verified by ATR-IR spectra and FESEM. The membrane surface hydrophobicity increased and the surface roughness decreased by the incorporation of fluorinated silica. In addition, the preparation conditions of TFN RO membranes incorporated with fluorinated silica nanoparticles, including IP reaction time, organic solvent removal time, and fluorinated silica loading, were optimized. The salt rejection increased dramatically from 96.0% without fluorinated silica nanoparticles to 98.6% with the optimal 0.12% (w/v) fluorinated silica nanoparticles in the organic phase, while the water flux decreased slightly from 0.99 m3/m2/day to 0.93 m3/m2/day. The modification of PA RO membrane by incorporating fluorinated silica nanoparticles could be applied successfully due to easy integration into the existing membrane manufacturing process. Moreover, the efficiency of desalination processes could be improved. Therefore, the hydrophobic nanoparticles can provide a facile and

promising approach to fabricate novel high-performance TFN RO membrane for practical applications. Acknowledgments This work was financially supported by the National Natural Science Foundation of China (Grant No. 51408581), Natural Science Foundation of Fujian Province (Grant

No.

2016J05143),

Bureau

of

International

Cooperation,

CAS

(132C35KYSB20160018) and Bureau of Frontier Sciences & Education, CAS (QYZDB-SSW-DQC044). References [1] J. Yin, B. Deng, Polymer-matrix nanocomposite membranes for water treatment, J. Membr. Sci. 479 (2015) 256–275. [2] M. Elimelech, W. A. Phillip, The future of seawater desalination: energy, technology, and the environment, Science 333 (2011) 712–717. [3] K. P. Lee, T. C. Arnot, D. Mattia, A review of reverse osmosis membrane materials for desalination—Development to date and future potential, J. Membr. Sci. 370 (2011) 1–22. [4] D. Li, H. Wang, Recent developments in reverse osmosis desalination membranes, J. Mater. Chem. 20 (2010) 4551–4566. [5] G. M. Geise, H. B. Park, A. C. Sagle, B. D. Freeman, J. E. McGrath, Water permeability and water/salt selectivity tradeoff in polymers for desalination, J. Membr. Sci. 369 (2011) 130–138. [6] D. Li, Y. Yan, H. Wang, Recent advances in polymer and polymer composite

membranes for reverse and forward osmosis processes, Prog. Polym. Sci. 61 (2016) 104–155. [7] S. S. Shenvi, A. M. Isloor, A. F. Ismail, A review on RO membrane technology: Developments and challenges, Desalination 368 (2015) 10–26. [8] S. Y. Lee, H. J. Kim, R. Patel, S. J. Im, J. H. Kim, B. R. Min, Silver nanoparticles immobilized on thin film composite polyamide membrane: characterization, nanofiltration, antifouling properties, Polym. Adv. Technol. 18 (2007) 562–568. [9] P. S. Singh, V. K. Aswal, Characterization of physical structure of silica nanoparticles encapsulated in polymeric structure of polyamide films, J. Colloid Interface Sci. 326 (2008) 176–185. [10] G. L. Jadav, V. K. Aswal, P. S. Singh, SANS study to probe nanoparticle dispersion in nanocomposite membranes of aromatic polyamide and functionalized silica nanoparticles, J. Colloid Interface Sci. 351 (2010) 304–314. [11] S. Y. Kwak, S. H. Kim, S. S. Kim, 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, Environ. Sci. Technol. 35 (2001) 2388–2394. [12] T. A. Saleh, V. K. Gupta, Synthesis and characterization of alumina nano-particles polyamide membrane with enhanced flux rejection performance, Sep. Purif. Technol. 89 (2012) 245–251. [13] H. Zhao, S. Qiu, L. Wu, L. Zhang, H. Chen, C. Gao, Improving the performance of polyamide reverse osmosis membrane by incorporation of modified multi-walled

carbon nanotubes, J. Membr. Sci. 450 (2014) 249–256. [14] W. F. Chan, H. Y. Chen, A. Surapathi, M. G. Taylor, X. H. Hao, E. Marand, J. K. Johnson, Zwitterion functionalized carbon nanotube/polyamide nanocomposite membranes for water desalination, ACS Nano 7 (2013) 5308–5319. [15] G. N. B. Baroña, J. Lim, M. Choi, B. Jung, Interfacial polymerization of polyamide-aluminosilicate SWNT nanocomposite membranes for reverse osmosis, Desalination 325 (2013) 138–147. [16] M. Ghanbari, D. Emadzadeh, W. J. Lau, S. O. Lai, T. Matsuura, A. F. Ismail, Synthesis and characterization of novel thin film nanocomposite (TFN) membranes embedded with halloysite nanotubes (HNTs) for water desalination, Desalination 358 (2015) 33–41. [17] H. R. Chae, J. Lee, C. H. Lee, I. C. Kim, P. K. Park, Graphene oxide-embedded thin-film composite reverse osmosis membrane with high flux, anti-biofouling, and chlorine resistance, J. Membr. Sci. 483 (2015) 128–135. [18] H. J. Kim, M. Y. Lim, K. H. Jung, D. G. Kim, J. C. Lee, High-performance reverse osmosis nanocomposite membranes containing the mixture of carbon nanotubes and graphene oxides, J. Mater. Chem. A 3 (2015) 6798–6809. [19] H Dong, L Wu, L Zhang, H Chen, C Gao, Clay nanosheets as charged filler materials for high-performance and fouling-resistant thin film nanocomposite membranes, J. Membr. Sci. 494 (2015) 92–103. [20] B. H. Jeong, E. M. V. Hoek, Y. S. Yan, A. Subramani, X. F. Huang, G. Hurwitz, A. K. Ghosh, A. Jawor, Interfacial polymerization of thin film nanocomposites: a new

concept for reverse osmosis membranes, J. Membr. Sci. 294 (2007) 1–7. [21] M. L. Lind, D. E. Suk, T. V. Nguyen, E. M. V. Hoek, Tailoring the structure of thin film nanocomposite membranes to achieve seawater RO membrane performance, Environ. Sci. Technol. 44 (21) (2010) 8230–8235. [22] M. L. Lind, A. K. Ghosh, A. Jawor, X. Huang, W. Hou, Y. Yang, E. M. V. Hoek, Influence of Zeolite Crystal Size on Zeolite-Polyamide Thin Film Nanocomposite Membranes, Langmuir 25(17) (2009) 10139–10145. [23] H. Dong, L. Zhao, L. Zhang, H. Chen, C. Gao, W. S. Winston Ho, High-flux reverse osmosis membranes incorporated with NaY zeolite nanoparticles for brackish water desalination, J. Membr. Sci. 476 (2015) 373–383. [24] H. Huang, X. Qu, X. Ji, X. Gao, L. Zhang, H. Chen, L. Hou, Acid and multivalent ion resistance of thin film nanocomposite RO membranes loaded with silicalite-1 nanozeolites, J. Mater. Chem. A 1 (2013) 11343–11349. [25] J. Duan, Y. Pan, F. Pacheco, E. Litwiller, Z. Lai, I. Pinnau, High-performance polyamide

thin-film-nanocomposite

reverse

osmosis

membranes

containing

hydrophobic zeolitic imidazolate framework-8, J. Membr. Sci. 476 (2015) 303–310. [26] J. Yin, E. S. Kim, J. Yang, B. Deng, Fabrication of a novel thin-film nanocomposite (TFN) membrane containing MCM-41 silica nanoparticles (NPs) for water purification, J.Membr.Sci. 423-424 (2012) 238–246. [27] E. S. Kim, B. Deng, Fabrication of polyamide thin-film nano-composite (PA-TFN) membrane with hydrophilized ordered mesoporous carbon (H-OMC) for water purifications, J. Membr. Sci. 375 (2011) 46–54.

[28] W. J. Lau, S. Gray, T. Matsuura, D. Emadzadeh, J. P. Chen, A. F. Ismail, A review on polyamide thin film nanocomposite (TFN) membranes: History, applications, challenges and approaches, Water Res. 80 (2015) 306–324. [29] J. R. Werber, A. Deshmukh, M. Elimelech, The critical need for increased selectivity, not increased water permeability, for desalination membranes, Environ. Sci. Technol. Lett. 3 (2016) 112−120. [30] Y. Zhang, R. Wang, Novel method for incorporating hydrophobic silica nanoparticles on polyetherimide hollow fiber membranes for CO2 absorption in a gas–liquid membrane contactor, J. Membr. Sci. 452 (2014) 379–389. [31] Y. Zhang, R. Wang, Fabrication of novel polyetherimide-fluorinated silica organic–inorganic composite hollow fiber membranes intended for membrane contactor application, J. Membr. Sci. 443 (2013) 170–180. [32] Y Zhou, S Yu, M Liu, C Gao, Preparation and characterization of polyamide-urethane thin-film composite membranes, Desalination 180 (2005) 189-196. [33] M Liu, S Yu, M Qia, Q Pan, C Gao, Impact of manufacture technique on seawater desalination performance of thin-film composite polyamide-urethane reverse osmosis membranes and their spiral wound elements, J. Membr. Sci. 348 (2010) 268–276. [34] H. Wang, J. Fang, T. Cheng, J. Ding, L. Qu, L. Dai, X. Wang, T. Lin, One-step coating of fluoro-containing silica nanoparticles for universal generation of surface superhydrophobicity, Chem. Commun. (2008) 877–879.

[35] L. Zhao, P. C. Y. Chang, W. S. W. Ho, High-flux reverse osmosis membranes incorporated with hydrophilic additives for brackish water desalination, Desalination 308 (2013) 225–232. [36] D. Rana, T. Matsuura, Surface modifications for antifouling membranes, Chem. Rev. 110 (2010) 2448–2471. [37] J. Yin, G. Zhu, B. Deng, Graphene oxide (GO) enhanced polyamide (PA) thin-film nanocomposite (TFN) membrane for water purification, Desalination 379 (2016) 93–101. [38] L Zhao, P. C. Y. Chang, C. Yen, W. S. W. Ho, High-flux and fouling-resistant membranes for brackish water desalination, J. Membr. Sci. 425–426 (2013) 1–10. [39] L. Zhao, W. S. W. Ho, Novel reverse osmosis membranes incorporated with a hydrophilic additive for seawater desalination, J. Membr. Sci. 455 (2014) 44–54. [40] A. K. Ghosh, B.-H. Jeong, X. Huang, E. M.V. Hoek, Impacts of reaction and curing conditions on polyamide composite reverse osmosis membrane properties, J. Membr. Sci. 311 (2008) 34–45.

Graphical abstract