Correlating PSf Support Physicochemical Properties with the Formation of Piperazine-Based Polyamide and Evaluating the Resultant Nanofiltration Membrane Performance.

Micah Ang,Wei-Song Hung,Shu-Hsien Huang,Hui-An Tsai,Alvin Caparanga,Yan-Li Ji,Quan-Fu An,Kueir-Rarn Lee,Chien-Chieh Hu,Juin-Yih Lai,Victor Lau

doi:10.3390/polym9100505

Abstract

Membrane support properties influence the performance of thin-film composite nanofiltration membranes. We fabricated several polysulfone (PSf) supports. The physicochemical properties of PSf were altered by adding polyethylene glycol (PEG) of varying molecular weights (200–35,000 g/mol). This alteration facilitated the formation of a thin polyamide layer on the PSf surface during the interfacial polymerization reaction involving an aqueous solution of piperazine containing 4-aminobenzoic acid and an organic solution of trimesoyl chloride. Attenuated total reflectance-Fourier transform infrared validated the presence of PEG in the membrane support. Scanning electron microscopy and atomic force microscopy illustrated that the thin-film polyamide layer morphology transformed from a rough to a smooth surface. A cross-flow filtration test indicated that a thin-film composite polyamide membrane comprising a PSf support (TFC-PEG20k) with a low surface porosity, small pore size, and suitable hydrophilicity delivered the highest water flux and separation efficiency (J = 81.1 ± 6.4 L·m−2·h−1, RNa2SO4 = 91.1% ± 1.8%, and RNaCl = 35.7% ± 3.1% at 0.60 MPa). This membrane had a molecular weight cutoff of 292 g/mol and also a high rejection for negatively charged dyes. Therefore, a PSf support exhibiting suitable physicochemical properties endowed a thin-film composite polyamide membrane with high performance.

Highlights

Polyamide membranes are widely used in solid or fluid separation technologies
molecular weight (MW) were 0, 200, 1000, 10,000, 20,000 and 35,000 g/mol, respectively. These results indicate that when high-MWW polyethylene glycol (PEG)
These results indicate that when a high-MW PEG was used, the formed polyamide had more carboxyl groups on the membrane surface

Summary

Introduction

Polyamide membranes are widely used in solid or fluid separation technologies. Numerous studies have demonstrated the competitiveness of polyamide membranes in nanofiltration (NF) [1,2], forwardPolymers 2017, 9, 505; doi:10.3390/polym9100505 www.mdpi.com/journal/polymersPolymers 2017, 9, 505 and reverse osmosis [2,3,4], dialysis [5], pervaporation [6,7,8,9,10], and gas separation [11,12,13]. Polyamide membranes are widely used in solid or fluid separation technologies. Interfacial polymerization (IP) is the primary method for fabricating high-performance NF polyamide membranes [39]. The following factors affect the morphology of the resulting thin film: the surface structure and polarity of the membrane support, the chemistry and concentration of monomer, solvent polarity, catalysts and additives, temperature and time during reaction and curing, and posttreatments [40,41,42,43,44]. Most studies focus on modifying the active layer or optimizing the monomer property and reaction process, rather than determining the effect of membrane support characteristics

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