Fabrication of Polyamide-6 Membranes-The Effect of Gelation Time towards Their Morphological, Physical and Transport Properties.

Mohammad Ebrahimi,Kateryna Fatyeyeva,Wojciech Kujawski

doi:10.3390/membranes12030315

Abstract

Porous polyamide-6 membranes were fabricated via a non-solvent induced phase inversion method, and the influence of gelation time on the properties of the membranes was investigated. Membrane samples with various gelation times were prepared. The evaluation of the membranes’ properties was carried out by various analyses and tests, such as scanning electron microscopy, atomic force microscopy, contact angle, wet and dry thickness, mean pore size measurements, porosity, water uptake, mechanical resistance, hydrodynamic water fluxes, membrane hydrodynamic permeability, and retention testing. The scanning electron microscopy images (both surface and cross-section) demonstrated that the increase in gelation time from 0 (M0) to 10 (M10) min led to the morphological change of membranes from isotropic (M0) to anisotropic (M10). The wet and dry thickness of the membranes showed a downward tendency with increasing gelation time. The M0 membrane exhibited the lowest bubble contact angle of 60 ± 4° and the lowest average surface roughness of 124 ± 22 nm. The highest values of mean pore size and porosity were observed for the M0 sample (0.710 ± 0.06 µm and 72 ± 2%, respectively), whereas the M10 membrane demonstrated the highest tensile strength of 4.1 MPa. The membrane water uptake was diminished from 62 to 39% by increasing the gelation time from 0 to 10 min. The M0 membrane also showed the highest hydrodynamic water flux among the prepared membranes, equal to 28.6 L m−2 h−1 (at Δp = 2 bar).

Highlights

Porous membranes are mainly classified into three categories: microfiltration, ultrafiltration, and nanofiltration membranes [1,2]
The images demonstrate that the increase in gelation time from 0 to 2 min does not change significantly the membrane’s apparent morphology, as the pore size of the M2 membrane is slightly smaller than that of the M0 membrane
With further increases in gelation time, the morphology of the membranes changed from an isotropic to an anisotropic one

Summary

Introduction

Porous membranes are mainly classified into three categories: microfiltration, ultrafiltration, and nanofiltration membranes [1,2]. The mean pore sizes of porous membranes lie between 0.2 nm and 10 μm [1,3]. Based on the separation process, different operating pressures are needed for porous membranes [4–6]. The driving force for the aforementioned processes is created by a pressure difference, meaning that by applying sufficient pressure onto the feed stream, separation will be occur [5,7]. Porous membranes are utilized in various fields such as the food, car, biotechnological, and electronic industries in order to separate a wide range of bacteria, yeast cells, macromolecules, colloids, viruses, aerosols, and smoke particles [2,3,8–10]. The filtration process for porous membranes can be carried out in two modes: dead-end and cross-flow [11,12]. Dead-end filtration is quite common, the fouling phenomenon occurs during the separation owing to the deposition of particles on the surface and/or in the membrane bulk [13,14]. Dead-end filtration was used to investigate the hydrodynamic permeability of polyamide-6 (PA6)

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Conclusion