Novel Hydrophobic/Hydrophilic Coated Membranes For Water Treatment Using Perfluoropolyether (PFPE) Compounds As Surface Modifier

Recently, most studies focus the attention to the preparation of tailored membranes in order to improve their performance. In fact, near the commonly preparation techniques, now the attention was focalized to the preparation of tailored membranes via coating technique, in order to produce high-performance membranes [1]. There are several methods used, such as solution coating or polymerization reaction. Hydrophilization and hydrophobization of membrane surface are the most commonly modification, that embrace different fields from the control of fouling to membrane distillation (MD). In this scenario, Solvay Specialty Polymers S.p.A., developed a novel class of Flurolink® perfluoropolyether (PFPE) compounds UV-curable as surface modifier [2]. Hydrophobic or super hydrophobic and oleophobic coated membranes can be easily prepared using hydrophilic cheaper membranes as supporting material, via dip-coating and UV in situ polymerization Fluorolink® MD700 PFPE UV cross-linkable, was used as coating material on two different hydrophilic commercial membranes, polyamide (PA) and polyethersulfone (PES) at three different pore size (0.1, 0.22 and 0.45 ?m). Initially the influence of starting material (PA-PES) was studied in terms of water/oil repellence. All covered membranes were characterized in terms of surface morphology (SEM and AFM), porosity and pore size, water liquid entry pressure (LEPw) and mechanical tests. The formation of a thin hydrophobic layer on the hydrophilic commercial membranes, make the membranes suitable for the membrane distillation process. Coating stability on membrane surface was then evaluated during time using salty solution NaCl 0.6 M, typical feed in desalination treatment and chemicals cleaning agents (KMnO4 0.1 wt.%, Hypochlorite NaClO pH 4.25, HCl pH 2.5, NaOH pH 11.5). Membranes performance were finally tested in DCMD configuration, using deionized water and salty solution 0.6M (NaCl), as feed. An highest value of permeate flux until 22 kg/m2h was obtained and concerning the tests with salty solution, a final salt rejections of about 99.95% after 158h of test was obtained for the best selected membrane [3]. [1] A. Figoli, C. Ursino, F. Galiano "Innovative Coating Membranes for Water Treatment", ch. 10 in Functional Nanostructured Membranes, Eds E. Drioli, L. Giorno, A. Gugliuzza, Pan Stanford, 2018, ISBN 978-981- 4774-79-6 [2] A. Figoli, C. Ursino, F. Galiano, E. Di Nicolò, P. Campanelli, M.C. Carnevale, A. Criscuoli "Innovative hydrophobic coating of perfluoropolyether (PFPE) on commercial hydrophilic membranes for DCMD application", Journal of Membrane Science 522 (2017) 192-201 [3] C. Ursino, E. Di Nicolò, B. Gabriele, A. Criscuoli, A. Figoli, "Development of a novel perfluoropolyether (PFPE) hydrophobic/hydrophilic coated membranes for water treatment", Journal of Membrane Science 581 (2019) 58-71