طراحي و ساخت غشا ژانوس بر پايه PVDF/PAN به روش الكتروريسي متوالي: بهره¬برداري از ترشوندگي سطح، تخلخل ساختار و اختلاف در ضخامت لايه¬هاي آب¬گريز /آب¬دوست در راستاي بهبود عملكرد جداسازي فاز آبي از فاز آلي

Janus membrane , Electrospinning , Asymmetric wettability , Directional water transport , Water an‎d oil separation , PVDF/PAN

Design an‎d fabrication of Janus membrane based on PVDF/PAN through sequential electrospinning technique: manipulation of surface wettability, structure porosity, an‎d thickness of hydro‎phobic- hydro‎philic layers to improve the separation performance of aqueous phase from organic phase

شيمي پليمر

Janus membranes have garnered significant attention due to their ability to facilitate unidirectional fluid transport an‎d their extensive applications in aqueous-organic phase separation. In this study, a PVDF/PAN Janus membrane was fabricated using electrospinning, an‎d its performance was optimized in terms of Laplace pressure, hydro‎philicity, porosity, an‎d mechanical properties. Initially, four types of Janus membranes with different morphologies—JInOn, JInOm, JImOn, an‎d JImOm—were designed an‎d eva‎luated. The minimum an‎d maximum fiber diameters for PAN an‎d PVDF polymers were measured at (172 ± 38 nm, 991 ± 99 nm) an‎d (139 ± 44 nm, 1002 ± 80 nm), respectively. Contact angle analysis revealed that the JInOm membrane, with the smallest fiber diameter in the hydro‎philic layer an‎d the largest in the hydro‎phobic layer, exhibited the best performance, achieving a total Laplace pressure of 205.60 kPa an‎d a dro‎plet penetration rate of 0.83 µL/s. This performance was attributed to the stronger wicking effect in the hydro‎philic layer an‎d the reduced hydro‎phobicity of the hydro‎phobic layer. In the second phase of the study, porosity within the PAN fiber layer was enhanced using selec‎tive removal (SR) an‎d non-solvent-induced phase separation (NIPS) methods. In the SR method, sacrificial components such as PVP, PEG, NaHCO₃, an‎d Na₂SO₄ were employed to create significant intrafiber porosity. Among these, NaHCO₃ produced the highest porosity (86%) due to CO₂ gas generation during its reaction with HCl. The internal pressure caused by CO₂ generation was the primary factor driving this increase in porosity. Comparatively, PEG outperformed PVP as a sacrificial component because residual PVP within the fiber matrix, confirmed through ATR-FTIR analysis, hindered porosity formation. The NIPS method, combined with vapor-induced phase separation (VIPS), also proved effective. Using a 5% non-solvent concentration provided optimal conditions for increasing porosity while maintaining mechanical properties. These methods improved hydro‎philicity an‎d simplified an‎d stabilized the electrospinning process. The third phase of the study focused on enhancing the hydro‎philicity of the PAN layer. Alkaline hydrolysis, a simple an‎d cost-effective method, was selec‎ted for this purpose. By converting nitrile groups into amide an‎d carboxylic acid groups, surface hydro‎philicity was increased. Analysis showed that a hydrolysis time of 18 minutes resulted in optimal conditions, reducing the contact angle to 32° an‎d improving water absorption. Prolonged hydrolysis times, however, negatively affected mechanical properties. The final membrane demonstrated a separation efficiency of 99.4 % an‎d a permeate flux of 12.2×104 L.m-2.h-1.bar-1 in water-oil mixture separation tests. By employing combined an‎d innovative modification approaches, this study successfully optimized the Laplace pressure, porosity, an‎d hydro‎philicity of the Janus membrane. The findings open new horizons for the design of advanced membranes tailored for industrial an‎d environmental applications.

4

122882