Effect of hydrophilic silica and dual coagulation bath on structural and mechanical properties of PVDF membrane for memb
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RESEARCH ARTICLE
Effect of hydrophilic silica and dual coagulation bath on structural and mechanical properties of PVDF membrane for membrane distillation Mohammad Hossein Emamirad 1 & Sirus Javadpour 1 Received: 6 September 2019 / Revised: 4 January 2020 / Accepted: 14 April 2020 # Springer Nature Switzerland AG 2020
Abstract The water scarcity threatens environmental health and human development. Membrane distillation (MD) is one of the most applicable processes for purifying water using a hydrophobic membrane. In this study, the synergetic effect of SiO2 nanoparticles as well as employing the dual coagulation bath on physical and mechanical properties of Polyvinylidene Fluoride (PVDF) flatsheet membranes produced by dry-wet phase inversion (DIPS) technique has been investigated. The results of microstructural analysis using Scanning Electron Microscope (SEM) demonstrated that by adding nanoparticles while the pore size decreased noticeably, the percentage of porosity significantly increased. Also, it has been revealed that by utilizing isopropanol as the first coagulation bath the finger-like macro-voids became smaller in size, and the share of sponge-like structures rose remarkably. The membrane performance was tested by Vacuum Membrane Distillation (VMD) for measuring the flux and Liquid Entry Pressure (LEPw) laboratory setup. It can be seen that by increasing the content of SiO2 nanoparticles to 6 wt.% while the LEPw approximately halved, the flux soared to about 10000 g/m2h. Moreover, mechanical testing showed that although the tensile strength of nanocomposite samples fabricated in isopropanol dual coagulation bath was improved by up to 66%, their ductility slightly declined. Furthermore, the hydrophobicity of each membrane was examined via contact angle measurements. Finally, it was found that all membranes completely rejected the NaCl in rejection test. Keywords PVDF nanocomposite membrane . Hydrophilic SiO2 nanoparticles . Mechanical properties . Membrane structure . Membrane distillation (MD)
Introduction Water shortage has been considered as one of the most critical environmental issues all over the world. Reverse osmosis (RO), Nanofiltration (NF) and membrane distillation (MD) processes were employed in sea and brackish water treatment. MD has been known as a suitable developing process for water desalination [1], which utilizes the vapor pressure differences to desalinate the saline water [2]. Appropriate membrane structures may result in high flux and salt rejection with high wetting and fouling resistance. With regards to improving the structure, rising the pore size and decreasing in tortuosity factor can lead to increasing in the flux of water. Also, * Sirus Javadpour [email protected] 1
Department of Materials Science and Engineering, School of Engineering, Shiraz University, Shiraz, Iran
wetting resistance improves whenever the average pore size tends to bubble point (BP) [3]. Moreover, it has been reported that the water contact angle (CA) and the bubble point tests could be used for
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