Synthesis and Surface Characterization of Magnetite ... - Science Direct

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ScienceDirect Procedia Materials Science 11 (2015) 342 – 346

5th International Biennial Conference on Ultrafine Grained and Nanostructured Materials, UFGNSM15

Synthesis and Surface Characterization of Magnetite-Titania Nanoparticles/Polyamide Nanocomposite Smart RO Membrane A. Tayefeha,c, S. A. Mousavib, M. Wiesnerc, R. Poursalehia,* a

Nanomaterials Group, Materials Engineering Department, Tarbiat Modares University, Tehran, P.O.Box:14115-111, Iran b Polymer Group, Department of Chemical and Petroleum Engineering, Sharif University of Technology, Tehran, Iran c Center of Environmental Implications of Nanotechnology (CEINT), Duke University, Durham, USA

Abstract In the water desalination technology, utilizing nanocomposite membranes have been an interesting approach to improve the water permeability and rejection properties of conventional reverse osmosis (RO) membranes. In this research, effects of magnetite (Fe3O4) and titania (TiO2) nanoparticles by loading in trimesoyl chloride (TMC) organic solution and in metaphenylene diamine (MPD) aqueous solutions on the surface characteristics of polyamide layer have been investigated. Also, the morphology and EDS line and map analysis of Fe3O4 coated PSf layer and in-situ reduced Fe3O4 by impregnation of precursors inside PSf layer after formation of PA top coat, have been considered. The morphology, dispersion of nanoparticles, surface bonds of magnetite and titania nanoparticles with polyamide and hydrophilicity of magnetic nanocomposite RO membrane has been taken into account in each method by scanning electron microscopy (SEM) , attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), X-ray diffraction (XRD) and contact angle measurement. Trace of nanoparticles inside membrane cross section has been analyzed by energy dispersive spectroscopy (EDS) method. The samples were implemented to the different magnetite nanoparticle weight percent caused to the variation of surface energy, contact angle, roughness and polyamide layer free bonds. In addition the optimum concentration of magnetite nanoparticles for improvement in surface properties of high efficiency reverse osmosis membrane was obtained. The results can provide a versatile technique for fabrication of high efficiency magnetic responsive nanocomposite smart RO membranes. © 2015Published The Authors. Published Elsevier Ltd.access article under the CC BY-NC-ND license © 2015 by Elsevier Ltd. by This is an open Peer-review under responsibility of the organizing committee of UFGNSM15. (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of UFGNSM15 Keywords: Reverse osmosis; nanocomposite; magnetite and titania nanoparticles; smart membrane.

* Corresponding author. Tel.: +98-21-82883997; fax: +98-21-82884390. E-mail address: [email protected]

2211-8128 © 2015 Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of UFGNSM15 doi:10.1016/j.mspro.2015.11.114

A. Tayefeh et al. / Procedia Materials Science 11 (2015) 342 – 346

1. Introduction Preparing fresh water from seawater or wastewater is known to be one of the most important issues and challenges in the environmental engineering, because of the current water shortage problems, mainly caused by the rapid growth of the world population and environment pollution, Paul (2012). Currently, polyamide membranes are widely used in the commercial RO systems because they offer a combination of high water flux and high rejections of the ions, Paul (2012). Recently, nanocomposite membranes containing nanomaterials such as metal oxide, silica nanoparticle, zeolite, graphene, graphene oxide, and carbon nanotube have been prepared to improve membranes properties and performances, Paul (2012), Fathizadeh et al. (2011), Li et al. (2009), Hu et al. (2013), J. Li et al. (2007), Lu et al. (2006). For instance, titanium dioxide and silver nanoparticles were incorporated into the membranes to increase antifouling and antibiofouling properties, Li et al. (2009), Dror-Ehre et al. (2012), and zeolite was embedded into RO membranes to improve the water flux, Fathizadeh et al. (2011). In this research magnetite (Fe3O4) and titania (TiO2) nanoparticles was incorporated to a thin film polyamide membrane via interfacial polymerization by two different route for preparing a new stimuli responsive smart TFN (thin film nanocomposite) RO membrane. Furthermore, effect of coating of PSf layer and also in-situ formation of magnetite by impregnation of precursors inside PSf layer on the morphology and EDS analysis of membrane cross section, as a new method for synthesis of nanocomposite membranes have been considered. The surface characteristics and membrane structure and chemical alteration were characterized by SEM, ATR-FTIR and contact angle measurement. The results can provide a versatile technique for fabrication of high efficiency magnetic nanocomposite smart RO membranes. 2. Experimental Polysulfone ultrafiltration membrane provided from Sharif University of Technology Membrane Center, used for fabrication of the TFN membranes, as substrate. 1,3-Phenylenediamine (MPD, 99%, Merck) and trimesoyl chloride (TMC, 98%, Merck) were the monomers used for the synthesis of the polyamide selective layer for thin film nanocomposite (TFN) membranes. Titanium dioxide nanoparticles (TiO2, Degussa P25) were used for modifying substrate properties. Furthermore, magnetite nanoparticles were synthesized by co-precipitation method as mentioned in Lu et al. (2007) also used. The RO substrates were fabricated by interfacial polymerization of polyamide on the polysulfone backing layer using a. TMC solutions in hexane containing 0 wt%, 1 wt%, 2wt% and 3wt% Fe3O4 nanoparticles, b. MPD solutions containing 0 wt% nanoparticle, 1 wt% TiO2, 1wt% Fe3O4, 1 wt% TiO2 together with 1 wt% Fe3O4. To make a. TMC organic and b. MPD aqueous colloidal suspensions, an appropriate amount of Fe3O4 nanoparticles and Fe3O4 together with TiO2 nanoparticles was first added into the TMC or MPD solutions. Then this solution underwent 30 min ultrasonication. In the method (a) At first, 50 ml of 2% (w/v) MPD aqueous solution was poured onto the top of polysulfone substrate surface and the solution was held on the surface for 2 min to ensure the penetration of MPD monomer in the pores of substrate followed by pouring 50 ml of 0.15% (w/v) TMC in n-hexane solution containing magnetite nanoparticles onto the substrate surface. And in the second method (b) At first, 50 ml of 2% (w/v) MPD aqueous solution containing nanoparticles was poured onto the top of polysulfone substrate surface and the solution was held on the surface for 2 min to ensure the penetration of MPD monomer in the pores of substrate followed by pouring 50 ml of 0.15% (w/v) TMC in n-hexane solution onto the substrate surface. Heat treatment was performed in an oven at 85oC for 5 min. Also, for coating the PSf layer with different weight percents of magnetite, an aqueous colloid of Fe3O4 poured on the pre-weighted PSf layer. Then by weighting the membrane 0.15 and 0.3 gr nanoparticles after rinsing membrane by DI water remained on the PSf layer. And for in-situ synthesis of magnetite inside and on top of the PSf layer we poured a specific amount of Iron chloride solutions on layer and after some minutes it was washed. Then by adding ammonium hydroxide the magnetite nanoparticles formed in and on the PSf layer. And finally, ATR-FTIR spectroscopy (Mode: FTLA 2000 series, ABB) was used to identify the functional groups. The IR-FTIR spectra for pure TiO2 and Fe3O4 powder was obtained from work of Cui and Murashkevich (2008). The membrane morphology studies were conducted with a SEM (Model: TM3000, Hitachi). The contact angle of substrate was measured by the sessile drop technique using digital microscope B005 model.

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3. Results and discussion The scanning electron microscopy images of membranes synthesized by adding nanoparticles to MPD and TMC aqueous and organic solutions in fig. 1, revealed nanocomposite membrane surfaces demonstrate the presence of external phase in the PA layer, the surface tend to more rough condition and also surface coverage lowered as the TiO2 or Fe3O4 or both of them are present in the PA layer. a

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Fig. 1. SEM images of surface and cross section of the thin film nanocomposite membranes synthesized by adding nanoparticles to MPD solution (a) and (e) PA/TiO2 layer; (b) and (f) PA/Fe3O4 layer and by adding to TMC solution; (c) and (g) 1wt% Fe3O4/polyamide layer; (d) and (h) 2wt% Fe3O4/polyamide layer.

Also as in the figures more entangled and lower rough surface in respect to low loadings in specimen results from TMC loaded nanocomposites. The nanocomposite membrane surfaces demonstrate the presence of external phase in the PA layer, the surface tend to more rough condition and also surface coverage lowered as the Fe 3O4 nanoparticles are present in the PA layer. Furthermore, the cross sections of specimens show the penetration of MPD suspension in the polysulfone layer and therefore polymerization in depth of polysulfone layer that caused to a rougher cross section. From the SEM images, it can be clearly observed that nanoparticle agglomeration took place on the top surface of membrane as the nanoparticles added. a

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Fig. 2. SEM images of membrane as (a) and (b) are 0.3 gr Fe3O4 coated PSf membrane surface and cross section; (c) and (d) are the surface and cross section of in-situ synthesized magnetite on and in the PSf layer.

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The permanent attachement of these nanoparticles to the polysulfone substrate matrix could be due to the combined effects of physical and chemical interactions. Also, as in fig. 2 by coating PSf layer with different amounts of magnetite nanoparticles and then PA formation of it, and by in-situ formation of magnetite on and in the PSf layer before PA formation, we can have different morphologies. By using EDS analysis in the cross section of synthesized membranes as in fig. 3, it was concluded that with magnetite coating we a concentrate region on top of the PSf membrane. However, in the in-situ synthesized magnetite in and on the PSf layer, we have a high concentrate and high penetrated region. Therefore it can be used as a method to embed such stimuli responsive nanoparticles inside the membrane. b

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Fig. 3. SEM EDS map and line scane of Iron atoms in (a) and (b) 0.3 gr Fe3O4 coated PSf and then PA formation on it; in (c) and (d) map and line scan of in-situ synthesized magnetite nanoparticles in the PSf layer.

Figure 4 presents the changes in the PA layer properties upon addition of different nanoparticles. As can be seen from thin bar diagram, the hydrophilicity of polysulfone substrate was significantly increased by the addition of hydrophilic TiO2 and Fe3O4 nanoparticles. And also, heat treatment caused to a slightly improvement in contact angle. However seawater as droplet test, showed higher contact angles in comparison to DI (deionized) water. a

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Fig. 4. Contact angle measurement of thin film nanocomposite membranes of the thin film nanocomposite membranes synthesized by adding nanoparticles to (a) MPD; (b) TMC solutions with sea water and DI water.

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Fig. 5. ATR-FTIR spectra of thin film nanocomposite membranes synthesized by adding nanoparticles to (a) MPD; (b) TMC solutions.

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An additional cause might be that the higher hydrophilicity of the MPD aqueous colloidal solution with the incorporation of nanoparticles, the inflow of water into the membrane during the interfacial polymerization favors. According to the contact angle experiments showed at fig. 4 for TMC loaded nanocomposites, with increasing the polymerization time contact angle increased. Also, the optimized condition for minimum contact angle can be in specimen with 2wt% Fe3O4 with 57o angle respect to deionized water. In all tests, sea water as droplet have 10 o lower contact angle in relation to deionized water, which it is due to lower surface energy of electrolyte water. Fig. 5 illustrates the ATR-FTIR spectra of neat PA layer and thin film nanocomposite membranes contained of TiO 2 and Fe3O4 nanoparticles. Following three typical characteristic peaks of formation of the polyamide layer can be seen in spectrums: in 1654 cm-1 corresponds to C=O bonds stretching vibration (amide I), 1545 cm -1 corresponds to N-H bonds of amide group (amide II), 1612 and 1488 cm -1 aromatic ring breathing in terms of C=C bond vibrations, and finally 1243 cm-1 (amide III). In specimen containing Fe3O4 nanoparticles due to decrease of specific bonds of polyamide as a barrier effect, there is a lower number of bonds and in the most of the regions absorbance of membrane was lower. In addition, there are following characteristic peaks which are corresponded to Fe-O bonds: 635 cm-1 for magnetite nanoparticles which is related to symmetrical tensional vibration of Fe-O bond. In addition as can be seen from Fig. 5 for TMC loaded nanocomposites, absorbance curve of the specimens between 600 to 2000 cm-1 has not a lot of bonds in comparison to polysulfone neat membrane. Thus presence of nanoparticle principally hindered the polyamide polymerization. According to the work of Cui (2008), 520, 500, 450, 430, 422 cm-1 are the characteristic peaks of the Fe3O4, which are exist in the infrared spectrum. In addition with increasing the Fe3O4 loading, the peaks related to Fe3O4 are amplified. 4. Conclusions From the experiments that was done, following results attained: by interfacial polymerization process we can synthesize nanocomposite membrane whether in colloid in TMC organic solution or in MPD aqueous one. Controlling the amount of nanoparticle loading affects on degree of polymerization of polyamide layer. The type of the nanoparticle can be a controlling factor to manipulate the characteristics of membrane surface. As it showed, by increasing the nanoparticles loading the surface roughness decreases and hydrophilicity can be better. It seems that by adding nanoparticles in MPD solution we have more control on dispersion, agglomeration and loading of them.

Acknowledgements We are grateful for the Lab-support received from the Sharif University of Technology Membrane Center. References Cui, S., 2008. Surface Organic Modification of Fe3O4 Magnetic Nanoparticles, Journal of Wuhan University of Technology-Mater. Sci 23, 436439. Dror-Ehre, A., Adin, A., 2012. Control of Membrane Biofouling by Silver Nanoparticles Using Pseudomonas Aeruginosa as a Model Bacterium, Desalin. Water Treat. 48, 130−137. Fathizadeh, M., Aroujalian, A., Raisi, A., 2011. Effect of Added NaX Nano-Zeoilite into Polyamide as a Top Thin Layer of membrane on Water Flux and Salt Rejection in a Reverse Osmosis Process, J. Membr. Sci 375, 88-95. Hu, M., Mi, B., 2013. Enabling Graphene Oxide Nanosheets as Water Separation Membranes, Environ. Sci. Technol. 47, 3715−3723. Li, D., Wang, H., 2010. RO Membrane State of the Art, J. Mater. Chem. 20, 4551−4556. Li, J., Xu, F., Yang, Z., Yu, H., 2009. Effect of TiO2 Nanoparticles on the Surface Morphology and Performance of Microporous PES Membrane, Appl. Surf. Sci. 255, 4725−4732. Li, J., Zho, Z., Zheng, M., 2007. Morphologies and Properties of Poly(phthalazinone ether sulfone ketone) Matrix Ultrafiltration Membranes with Entrapped TiO2 Nanoparticles, J. Appl. Polym. Sci. 103, 3623−3629. Lu, A., Salabas, E., Schüth, F., 2007. Magnetic Nanoparticles: Synthesis, Protection, Functionalization, and Application, Angewandte Chemie – International Edition 46, 1222–1244. Lu, L., Sun, H., Peng, F., 2006. Novel Graphite-Filled PVA/CS Hybrid Membrane for Pervaporation of Benzene/Cyclohexane Mixtures, J. Membr. Sci. 281, 245−252. Murashkevich, A., 2008. Infrared Absorption Spectra and Structure of TiO2-SiO2 Composites, Journal of Applied Spectroscopy 75, 730-734. Paul, D. R., 2012. Creating New Types of Carbon-Based Membranes, Science 335, 413−414.