IOP Conference Series: Materials Science and Engineering Related content PAPER • OPEN ACCESS Preparation of various nanofibrous composite membranes using wire electrospinning for oilwater separation - Recent progress concerning the production of controlled highly oriented electrospun nanofibrous arrays L R Manea, L Hristian, A L Leon et al. To cite this article: Fatma Yalcinkaya et al 2017 IOP Conf. Ser.: Mater. Sci. Eng. 254 102011 - Underwater superoleophobic stainless steel mesh fabricated by laser cladding a copper foil for oil–water separation Bingge Li, Zhongxu Lian, Huadong Yu et al. View the article online for updates and enhancements. - In situ growth of hierarchical Al2O3 nanostructures onto TiO2 nanofibers surface: super-hydrophilicity, efficient oil/water separation and dye-removal Wanlin Fu, Yunqian Dai, Jilan Tian et al. Recent citations - A review on advanced nanofiber technology for membrane distillation Fatma Yalcinkaya - Surface modification of electrospun nanofibrous membranes for oily wastewater separation Fatma Yalcinkaya et al This content was downloaded from IP address 198.12.91.14 on 17/01/2019 at 05:18 17th World Textile Conference AUTEX 2017- Textiles - Shaping the Future IOP Publishing IOP Conf. Series: Materials Science and Engineering 254 (2017) 102011 doi:10.1088/1757-899X/254/10/102011 1234567890 Preparation of various nanofibrous composite membranes using wire electrospinning for oil-water separation Fatma, Yalcinkaya1, Anna Siekierka2, Marek Bryjak2 and Jiri Maryska1 1 Technical University of Liberec, Centre for Nanomaterials, Advanced Technology and Innovation, Department of Nanotechnology and Informatics, Studentska 1402/2, 461 17, Liberec, Czech Republic 2 Wroclaw University of Technology, Faculty of Chemistry, 27 Wyb. Wyspianskiego, 50-370 Wroclaw, Poland Abstract Due to growing demand for production of safe water a search of new materials for water purification is of critical issue. Their production should be of low cost and offers easily scalable manufacturing protocol. In this study, we have described preparation and properties of hydrophilic/oleophobic microfiltration membranes produced by means of wire electrospinning. Selective separation of oil or water was tested for oil-water emulsion by using a dead-end filtration unit. The obtained data allowed us to claim membranes as excellent separators for splitting emulsions. Introduction During the past decades, membrane separation has become an emerging technology for such industries as beverages, starch and sweetener, pharmaceutical, petrochemical, bulk chemical, water treatment, dairy and so on. The useful membrane processes are microfiltration, nanofiltration, ultrafiltration, reverse osmosis, forward osmosis, electrodialysis, and gas separation. The selection of a membrane is a key element for the optimum efficiency of the process. The membranes and the separation process should be selected based on the application area. For instance, a microfilter is one of the efficient material to separate oil droplets from oil-water emulsion [1–4]. It is characterized by permeate flux, that shows the amount of medium passing through membrane, and by selectivity describing preferential transportation of one compound over others. Polypropylene (PP) nonwoven mats have been widely used in oil spill cleanup due to their oleophilic properties, good oil-water selectivity and easiness of fabrication. However, oil sorption capacity of PP nonwovens is limited due to large fiber diameters [5–7]. To bypass that obstacle nanofibers from polyvinylidene fluoride (PVDF) or polystyrene (PS) have been used frequently for oil-water separation [7, 8]. In this study, needle-free wire electrospinning system was used for the production of nanofiber webs. Polyacrylonitrile (PAN) and PVDF were selected for oil-water emulsion. PAN is highly polar and hydrophilic polymer while PVDF has hydrophobic character with high chemical resistance and excellent mechanical strength. In our previous work, it was found that PAN nanofibers had weak mechanical strength in comparison to PVDF [9]. Hence, we assumed that blends of PVDF and PAN should give nanofibers with better mechanical properties that neat PAN. To the best of our knowledge, only few works have reported improvement of strength [10, 11]. However, raising the mechanical strength did not fully characterize the searched microfilter. Hence, the second membrane metrics, their separation efficiency, had to be evaluated. In this study, we investigated nanofibrous Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Published under licence by IOP Publishing Ltd 1 17th World Textile Conference AUTEX 2017- Textiles - Shaping the Future IOP Publishing IOP Conf. Series: Materials Science and Engineering 254 (2017) 102011 doi:10.1088/1757-899X/254/10/102011 1234567890 composite PVDF, PAN and PVDF/PAN membranes with a high specific surface area, directly prepared via wire electrospinning device without any post treatment, for the use as oil-water separators. Materials and Methods 8% wt. polyacrylonitrile (Mw=150 kDa, purchased from Dicherma, China) was dissolved in dimethylformamide while 13% wt. polyvinylidene fluoride (donated from Kynar, France) was dissolved in dimethylacetamide. The solvents were purchased from Penta, s.r.o., Czech Republic. Solutions were mixed over the night at a temperature 50°C. The mixtures for electrospinning were prepared as shown in Table 1. Needle-free wire electrospinning device (Figure 1) was used for electrospun of nanofiber web under stable electrospinning conditions in a close chamber. All the samples were laminated with a 120 g/m2 polyester spunbond nonwoven web to improve mechanical stability. The surface of the membranes was characterized by Scanning Electron Microscope (SEM, Vega 3SB) and fiber diameter were analyzed by Image-J program. An 1200-AEL capillary flow porometer (Porous Media Inc., Ithaca, NY) was used to measure the pore size and pore distribution. Table 1. The code for each sample, the ratio of polymers, area weight and pore size of nanofibers. Sample code PVDF/PAN wt. ratio P1 1/0 P2 0/1 P3 2/1 P4 1/1 P5 1/2 Area weight Pore size 3.52 ± 0.5 g/m2 2030± 562 nm 1.29 ± 0.5 g/m2 710± 344 nm 1.99 ± 0.5 g/m2 790± 516 nm 4.35 ± 0.5 g/m2 910± 245 nm 0.72 ± 0.5 g/m2 820± 324 nm Figure 1. Schematic illustration of wire electrospinning device; (A) a solution tank feeds the solution toward the wire, (B) wire electrode, (C) spinning area, (D) take-up cylinder connected to supporting material, (E) high voltage supply. An Amicon 8050 dead-end filtration cell was used for microfiltration test. Feed solution was prepared by mixing of distilled water/vegan oil with the volume ration of 1/1. Water was colored by methylene blue to observe the separation process properly. At the beginning of each filtration, 20 mL of distilled water was pumped throughout membrane. The cell was filled with 50 mL of emulsion and pressurized 2 17th World Textile Conference AUTEX 2017- Textiles - Shaping the Future IOP Publishing IOP Conf. Series: Materials Science and Engineering 254 (2017) 102011 doi:10.1088/1757-899X/254/10/102011 1234567890 to 0.02 bar. For each test, 15 mL of permeate was collected. It was kept in a glass tube for 24 hours to determine water and oil volumes. Results and Discussion Surface Analysis and Characterization of Membranes SEM images of the samples are shown as in Figure 2. The data revealed that PVDF nanofiber had almost 2.5 times larger diameter compared to PAN nanofibers. Mixing of PVDF with PAN decreases the diameter of the fibers nearly 1.6 times compared to neat PVDF fibers. It is well-known that nanofiber diameter has an influence on the pore diameter of the nanofibrous membranes [12, 13]. Lowery suggested that there is a strong correlation between the diameters of fiber and pore of electrospun mats produced under the same conditions [14]. PVDF nanofibers have better mechanical properties compared to PAN nanofibers. Even a slight tension can easily damage the PAN material. On the other hand, PAN nanofiber web has lower fiber diameter and pore size compared to PVDF. Blending of these two polymers results in mechanical properties and pore size. It was found that mixture of PVDF and PAN increase improves hydrophilicity of the obtained material [9]. 3 17th World Textile Conference AUTEX 2017- Textiles - Shaping the Future IOP Publishing IOP Conf. Series: Materials Science and Engineering 254 (2017) 102011 doi:10.1088/1757-899X/254/10/102011 1234567890 Figure 2. SEM images and fiber diameter distribution of nanofiber webs Oil-Water Separation Separation of oil-water emulsions is always difficult and some microfilters are used for that purpose. Nanofibrous membranes of PAN, PVDF and their blends were tested for oil-water separation. The permeate flux (F) and the permeability (k) of the membrane were calculated (Eq. (1) and (2)): F= L/hm2 k = F/P L/hm2bar 4 (1) (2) 17th World Textile Conference AUTEX 2017- Textiles - Shaping the Future IOP Publishing IOP Conf. Series: Materials Science and Engineering 254 (2017) 102011 doi:10.1088/1757-899X/254/10/102011 1234567890 where A is the effective membrane area (m2), V is the total volume of permeate (F), P is transmembrane pressure (bar), and t is the filtration time (h) [11]. The permeability of the membranes is shown in Figure 3. Figure 3. Oil-water permeability of the various nanofibrous membranes It is well-known that PAN has a highly polar group which impart to the hydrophilicity of the membrane. The permeability test showed that PAN nanofibrous membranes have the highest permeability compared to other membranes. The permeability of the PVDF/PAN samples increased with the amount of PAN in the mixture. Oppositely, PVDF nanofibrous membrane selectively separate oil from the water; only oil passed through the PVDF membrane as the polymer had hydrophobic character. Its low surface energy (25 dynes cm-1) generated membrane oleophilicity expressed in water contact angle of 158° and oil contact angle less than 1° [15]. Figure 4. Permeate solution after separation of the oil-water emulsion. The permeate solution was collected and kept for 24 hours to determine oil/water content (Figure 4). The results are listed in Table 2. Table 2. Comparison of oil-water fraction of the permeate solution for various membranes. Sample code Polymer ratio (PVDF/PAN) Oil/water ratio (%) P1 1/0 100/0 P2 0/1 0/100 P3 2/1 100/0 P4 1/1 50/50 P5 1/2 27/73 The results showed that the PVDF nanofibrous membranes allowed oil to permeate mostly while PAN membranes induced water permeability. Moreover, the neat PAN membranes had higher permeability than other membranes. The oil-water permeability of the PVDF/PAN mixture depends on the fraction of polymer in the blend. Sample P5 showed oleophobic character while sample P3 was characterized 5 17th World Textile Conference AUTEX 2017- Textiles - Shaping the Future IOP Publishing IOP Conf. Series: Materials Science and Engineering 254 (2017) 102011 doi:10.1088/1757-899X/254/10/102011 1234567890 by oleophilicity. It pointed that PVDF affected the surface character of the prepared material. The oil content of permeate remarkably decreased by raising the amount of PAN in the polymer blend. These results indicated higher oil rejection could be achieved by using neat PAN. However, the neat PAN nanofibers are fragile and can be easily damaged. It seems to us that PVDF polymer could be added to PAN in lower ratio than 1/2 to strengthen the membrane stability. Evaluation of mechanical improvements will be subject of our future work. Conclusion In this work, we have developed nanofibrous composite membranes for oil-water separation without any post treatment. A facile, inexpensive method for the fabrication of nanofibrous webs was used. Two polymer PVDF and PAN was selected for electrospinning. Their blends affected the separation of oil-water emulsions. The neat PAN nanofibrous membranes showed the best water permeability while neat PVDF facilitated oil permeability. Significant achievements were made in study on the use of electrospun materials as microfilters for separation of oil-water emulsions. We believe that this kind of microfilters is a promising candidate for the use in the large-scale removal of oily aqueous streems. However, the additional studies on these membranes are needed to better understand their properties. Acknowledgement The authors are grateful for financial support from the project LO1201 was obtained through the financial support of the Ministry of Education, Youth and Sports in the framework of the targeted support of the “National Programme for Sustainability I” and the Mobility Fond TUL 2016. Special thanks to Ms. Tamara Pavlovova and Mr. Jerome Chauveau, Kynar Arkema (Bratislava and France) for their kind cooperation. References [1] Zahid M A, Halligan J E and Johnson R F. 1972 Oil Slick Removal Using Matrices of Polypropylene Filaments Ind Eng Chem Process Des Dev 11 (4) pp 550–555. [2] Lin Q, Mendelssohn I A, Carney K, Miles S M, Bryner N P and Walton W D 2005 In-situ Burning of Oil in Coastal Marshes. 2. Oil Spill Cleanup Efficiency as a Function of Oil Type, Marsh Type, and Water Depth Environ Sci Technol. 39 (6) pp 1855–1860. [3] Lessard R R and DeMarco G 2000 The Significance of Oil Spill Dispersants Spill Science and Technology Bulletin 6 (1) pp 59–68. [4] Fujita I, Yoshie M, Mizutani M, San M, Fudo M and Tatsuguchi M 2004 An Onboard Vacuum Suction Spilled Oil Recovery System Oceans ’04 Mts/Ieee Techno Conference Proceedings 1-4 pp 1458-1463. [5] Choi H M and Cloud R M. 1992 Natural Sorbents in Oil Spill Cleanup Environ Sci Technol. 26 (4) pp 772–776. [6] Choi H M, Kwon H J and Moreau J P 1993 Cotton Nonwovens as Oil Spill Cleanup Sorbents Textile Research Journal 63 (4) pp 211–218. [7] Lin J, Shang Y, Ding B, Yang J and Yu J and Al-Deyab S S 2012 Nanoporous Polystyrene Fibers for Oil Spill Cleanup Mar Pollut Bull. 64 (2) pp 347–352. [8] Jiang Z, Tijing L D, Amarjargal A, Park C H, An KJ, Shon H K and Cheol S K 2015 Removal of Oil From Water Using Magnetic Bicomponent Composite Nanofibers Fabricated by Electrospinning Compos Part B Eng. 77 pp 311–318. [9] Yalcinkaya F. Preparation of Various Nanofiber Layers Using Wire Electrospinning System 2016 Arab J Chem. DOI: 10.1016/j.arabjc.2016.12.012 [10] Yalcinkaya B, Yalcinkaya F and Chaloupek J 2016 Thin Film Nanofibrous Composite Membrane for Dead-End Seawater Desalination J Nanomater. 2016 12 pages. [11] Yalcinkaya F, Yalcinkaya B, Hruza J and Hrabak P 2017 Effect of Nanofibrous Membrane 6 17th World Textile Conference AUTEX 2017- Textiles - Shaping the Future IOP Publishing IOP Conf. Series: Materials Science and Engineering 254 (2017) 102011 doi:10.1088/1757-899X/254/10/102011 1234567890 [12] [13] [14] [15] Structures on the Treatment of Wastewater Microfiltration Sci Adv Mater. 9 pp 747–757. Tavanai H, Jalili R and Morshed M 2009 Effects of Fiber Diameter and CO 2 Activation Temperature on the Pore Characteristics of Polyacrylonitrile Based Activated Carbon Nanofibers Surf Interface Anal. 41 (10) pp 814-819. Matsumoto K, Yunoki T and Nakamura K 2004 Effect of Fiber Diameter, Porosity and Basis Weight on Pore Size and Pore Size Distribution of Stainless Steel Non-woven Fiber Filter Kagaku Kogaku Ronbun. 30 (1) pp 79–86. Lowery J L, Datta N and Rutledge G C 2010 Effect of Fiber Diameter, Pore Size and Seeding Method on Growth of Human Dermal Fibroblasts in Electrospun Poly(ε-caprolactone) Fibrous Mats Biomaterials. 31 (3) pp 491–504. Zhang W, Shi Z, Zhang F, Liu X, Jin J and Jiang L 2013 Superhydrophobic and Superoleophilic PVDF Membranes for Effective Separation of Water-In-Oil Emulsions With High Flux. Adv Mater 25 (14) pp 2071–2076. Corresponding author: Fatma YALCINKAYA Technical University of Liberec, Institute for Nanomaterials, Advanced Technology and Innovation, Department of Nanotechnology and Informatics E-mail: yenertex@hotmail.com 7