Nanofiltration thin‐film composite membrane on either the internal or the external surface of a polysulfone hollow fiber

Abstract

The inner and outer surfaces of a porous hollow fiber polysulfone support are compared as substrates for the synthesis of polyamide thin-film composite (TFC) membranes by interfacial polymerization. While both surfaces have pores common of microfiltration membranes, the inner surface has a larger pore diameter than the outer surface (2,700 nm compared to 950 nm). The inner TFC membrane showed higher water nanofiltration permeance than the outer (2.20 ± 0.17 compared to 0.13 ± 0.03 L m −2 hr −1 bar −1 ). This was due to the influence of the porosity and roughness, which were different on both support surfaces. These membranes are interesting because they were synthesized in a hollow fiber support with a high membrane area per volume unit (~6,900 m 2 /m 3 ) and the substrate used was commercial, which means that the TFC membrane obtained is suitable for industrial application. A mathematical simulation of the nanofiltration run with COMSOL Multiphysics 5.3 software confirmed the experimental trends observed. K E Y W O R D S hollow fiber, interfacial polymerization, microfluidics, nanofiltration, thin-film composite

Polyamide-MIL-101(Cr) Thin Films Synthesized on Either the Outer or Inner Surfaces of a Polysulfone Hollow Fiber for Water Nanofiltration

“…Similarly, the inner surface is rougher than the outer surface (an average roughness of 1000 ± 660 nm compared to 270 ± 50 nm), as it can be seen in the AFM 3D models of Figure D,E. Even if the current work is focused on only one type of support, especially suitable due to its commercial application and availability, the influence of the support on the synthesis of TFC membranes has been addressed by several authors from the point of view of porosity and hydrophobicity. , One of the key issues deals with its chemical composition, while for water nanofiltration applications, PSf are suitable, and in the case of organic solvent nanofiltration, solvent-resistant polymers submitted to cross-linking are applied. , …”

“…As shown in Figure 8, the water permeance values were higher through the TFC_in membrane than through the TFC_out membrane at any test time (2.2 ± 0.2 and 0.13 ± 0.02 L•m −2 • h −1 •bar −1 at 6 h, respectively). These membranes were tested in a previous investigation, 25 obtaining similar permeance values as that predicted in a COMSOL simulation. The research led to the conclusion that the differences between the outer and inner surface morphologies played a critical role in the properties of the PA thin films: the outer PA film permeance is significantly lower than that of the inner.…”

“…IP assisted by microfluidic means was applied to synthesize the PA thin film on the inner surface of a 12 cm long HF support, as we did in a previous research related to TFC and MOF membranes. , Using a syringe pump, the MPD solution, whose composition was identical to that used in the previous synthesis (2% w/v), was fed to the fiber inside at a rate of 70 μL/min for 5 min. Pure cyclohexane (Scharlab, extra pure) was then pumped with a different syringe pump at a rate of 157 μL/min for 1 min to remove the excess MPD solution from the lumen side.…”

“…For the synthesis of the thin film on the outer surface of the HF, a method recently published was followed. 25 We first immersed a piece of HF 12 cm long in an aqueous solution with a 2% (w/v) of MPD for 2 min. After that, the excess solution was removed with tissue paper.…”

Alicyclic polyamide nanofilms with an asymmetric structure for Cl−/SO42−separation

“…Conventional PA NF membranes exhibit a composite structure, whereby an active layer is formed via interfacial polymerization (IP) through trimesic acid chloride (TMC) and piperazine (PIP) atop a porous support layer formed via phase inversion. 8 Based on the size exclusion and Donnan equilibrium effects, the above semiaromatic PA (TMC-PIP) NF membrane achieves an unsatisfactory separation selectivity for Cl À and SO 4 2À in the separation process. [9][10][11] Although extensive research has been conducted to decrease the thickness of the PA nanofilm to increase the membrane permeance, the majority of the conventional IP process lacks control of the molecular-level design of the PA layer required to accomplish a high separation rate of ions in regard to composite membrane specification.…”