Fabrication of highly efficient nanofiltration membranes decorated with praseodymium based triamino-functionalized MCM-41 for desalination and micropollutants removal

Abstract

The nanofiltration membranes with a stable decoration of inorganic fillers such as zeolites are desperately required for enhancing the desalination performance of the membranes and hence three nanofiltration membranes were fabricated by decorating the membranes with praseodymium-based triamino-functionalized MCM-41 (Pr-(NH)2NH2-MCM-41). The membranes were applied for the removal of emerging pharmaceutically active micropollutants from water. The Pr-(NH)2NH2-MCM-41 was synthesized by using an in-situ approach where praseodymium oxide was chemically decorated in the framework of MCM-41 followed by simultaneous amine functionalization using N1-(3-Trimethoxysilylpropyl)diethylenetriamine (TMSPTA). A thorough characterization of the synthesized Pr-(NH)2NH2-MCM-41 was carried out by using HR-TEM, SEM, WCA, XRD, FTIR, BET, elemental and mapping analysis. Three different concentrations of synthesized Pr-(NH)2NH2-MCM-41 were decorated in the membrane active layer through interfacial polymerization in the presence of an aqueous tetra-amine solution and using terephthaloyl chloride as an organic crosslinker. Subsequently, the fabricated membranes were used for desalinating saline feed containing divalent (CaCl2, MgCl2, Na2SO4, MgSO4) and monovalent (NaCl) ions. The rejection of salts by PA/0.05-Pr-MCM@PSU/PET membrane was found to be the highest among all the fabricated membranes which were found to be 98 %, 96 %, 95 %, 87 %, and 82 % for CaCl2, MgCl2, MgSO4, Na2SO4 and NaCl, respectively. The permeate flux was found to be dependent on the applied feed pressure which was found to be 56 L m-2 h-1 (LMH) at 25 bar for PA/0.050-Pr-MCM@PSU/PET membrane. The rejection performance of the membranes was also evaluated by using different well-known pharmaceuticals (Caffeine, Sulfamethoxazole, Amitriptyline, and Loperamide) as micropollutants in the feed. All the pharmaceutical drugs were found to be highly rejected > 96 % by PA/0.5-Pr-MCM-41@PSU/PET membrane followed by PA/0.025-Pr-MCM-41@PSU/PET membrane. Therefore, the current approach of synthesizing functionalized zeolites is quite effective and efficient for the stable decoration of inorganic fillers in the membrane active layer and should be extended to other zeolites such as zeolites with antimicrobial potential.