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Free Radical Graft Copolymerization Strategy To Prepare Catechin-Modified Chitosan Loose Nanofiltration (NF) Membrane for Dye Desalination

Liu, Songbai, Wang, Zhan, Song, Peng
ACS sustainable chemistry & engineering 2018 v.6 no.3 pp. 4253-4263
Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, atomic force microscopy, catechin, chitosan, contact angle, copolymerization, desalination, fouling, free radicals, gentian violet, hydrolysis, magnesium chloride, magnesium sulfate, nanofiltration, polyacrylonitrile, scanning electron microscopy, sodium chloride, sodium sulfate, ultrafiltration
In this study, a novel free radical graft copolymerization strategy was applied to prepare the catechin-modified chitosan loose nanofiltration (NF) membrane for dye desalination. First, catechin, the eco-friendly natural material, was grafted onto chitosan through a free radical reaction and self-cross-linking. Second, the catechin-grafted-chitosan conjugates were assembled onto the surface of the hydrolyzed polyacrylonitrile (HPAN) ultrafiltration (UF) membrane. Finally, the prepared membrane was characterized by FT-IR, XPS, SEM, AFM, electrokinetic analyzer, and contact angle goniometer. The results showed that the prepared membrane exhibited a high rejection for dyes (i.e., 99.6% for congo red, 98.7% for acid fuchsin, and 98.5% for crystal violet) and a low retention for inorganic salts (i.e., 4.8% for Na₂SO₄, 12.5% for NaCl, 15.8% for MgSO₄, and 16.2% for MgCl₂). The Na₂SO₄ rejection, especially, was 2–3 times lower than that of the reported loose NF membranes. Meanwhile, a high removal rate of 82% for NaCl with a dye loss rate of 10% was also observed in the constant-volume batch dye desalination process. Moreover, the membrane also possessed a good dye antifouling ability with a flux recovery ratio of 87.8% and an irreversible fouling ratio of 12.2%. Hence, this catechin-modified chitosan loose NF membrane shows a promising application for dye desalination.