Influence of PVDF concentration on the morphology, surface roughness, crystalline structure, and filtration separation properties of semicrystalline phase inversion polymeric membranes

Abstract

To cite this article: A. Akbari , M. Hamadanian , V. Jabbari , A. Yunessnia Lehi & M. Bojaran (2012) Influence of PVDF concentration on the morphology, surface roughness, crystalline structure, and filtration separation properties of semicrystalline phase inversion polymeric membranes, Desalination and Water Treatment, 46:1-3, 96-106, A B S T R A C TThis study was focused on the fabrication of nanoporous poly(vinylidene fluoride) (PVDF) membranes at different polymer concentration (14, 17, and 20 wt%) via phase inversion method. The morphology and surface roughness of the resulting membranes were investigated by scanning electron microscopy (SEM) and atomic force microscope, respectively. SEM results showed that with the increase of polymer concentration, the pore size of membranes and the overall porosity decrease. Also, the results showed that varying concentration results in significant changes on the surface roughness. Analysis of the crystalline structures of PVDF membranes by X-ray diffraction showed that the membranes, which precipitated in the higher concentration of polymer (20 wt%) had a typical "b" form of the crystalline phase, whereas those membranes that formed at lower concentration (14 wt%) showed crystallites of the "a + b" form of the crystalline phase. Furthermore, the filtration separation experiments of Acid Yellow 23 (AY23) were conducted to examine the effects of concentration parameter on the performance of nanoporous PVDF membranes. Results showed that the retention of AY23 increases as the polymer concentration increases and an efficiency of 89.72% was achieved in polymer concentration of 20 wt%.

Hydrophobic asymmetric ultrafiltration PVDF membranes: an alternative separator for VFB with excellent stability

“…With increasing PVDF concentration in the casting solutions, both the vanadium ion and the proton permeabilities decrease, which agrees well with the anticipated decreasing pore size distribution of the resulting membranes. 21 To our surprise, compared with the earlier reported hydrophilic PAN-H nanofiltration membranes with much smaller pore sizes, the vanadium ion permeability is much lower through the more open PVDF (5 Â 10 À6 Vs. ).…”

“…Similarly, with the membranes prepared from casting solutions with different concentrations, an increased thickness slows down the phase inversion process at the bottom side of the membrane. 19 The magnified sponge structures of the membranes with different thicknesses clearly indicate that with increasing thickness, some spherical particles, generally referred to as nodules, 18 become formed, most probably induced by some crystallization of the PVDF. Moreover, a sandwich-like structure with two skin layers was found for the membrane with a thickness of 125 mm, which possibly creates an additional ion selectivity in the VFB.…”

Nodular structure and crystallinity of poly(vinylidene fluoride) membranes: Impact on the performance of direct‐contact membrane distillation for nutrient isolation

“…The obtained results agree well with the SEM images reported in Figure , in which the pore size and porosity became smaller with increasing polymer concentrations. In general, a higher polymer concentration produced a membrane with smaller granular structure, and this enhanced the polymer packing density . Smaller nodules gave a more compact structure compared to the bigger nodules.…”

“…This was the reason the surface of M‐12 had a higher roughness (0.886 µm) compared to M‐20 (0.494 µm). In general, a higher polymer concentration produced a smaller granular structure, which enhanced the polymer packing density …”

“…An enormous amount of work on membrane fabrication has been conducted to optimize and enhance the performance of PVDF membranes . Topics studied have included the composition of polymer solution (polymer concentration, solvent, cosolvent, additives, and their respective concentrations), the type of membrane material, the type of support material (polymer, glass, metal, nonwovens, etc.…”