Nanofiltration Membranes Formed through Interfacial Polymerization Involving Cycloalkane Amine Monomer and Trimesoyl Chloride Showing Some Tolerance to Chlorine during Dye Desalination

Abstract

Wastewater effluents containing high concentrations of dyes are highly toxic to the environment and aquatic organisms. Recycle and reuse of both water and dye in textile industries can save energy and costs. Thus, new materials are being explored to fabricate highly efficient nanofiltration membranes for fulfilling industrial needs. In this work, three diamines, 1,4-cyclohexanediamine (CHD), ethylenediamine (EDA), and p-phenylenediamine (PPD), are reacted with TMC separately to fabricate a thin film composite polyamide membrane for dye desalination. Their chemical structures are different, with the difference located in the middle of two terminal amines. The surface morphology, roughness, and thickness of the polyamide layer are dependent on the reactivity of the diamines with TMC. EDA has a short linear alkane chain, which can easily react with TMC, forming a very dense selective layer. CHD has a cyclohexane ring, making it more sterically hindered than EDA. As such, CHD’s reaction with TMC is slower than EDA’s, leading to a thinner polyamide layer. PPD has a benzene ring, which should make it the most sterically hindered structure; however, its benzene ring has a pi-pi interaction with TMC that can facilitate a faster reaction between PPD and TMC, leading to a thicker polyamide layer. Among the TFC membranes, TFCCHD exhibited the highest separation efficiency (pure water flux = 192.13 ± 7.11 L∙m−2∙h−1, dye rejection = 99.92 ± 0.10%, and NaCl rejection = 15.46 ± 1.68% at 6 bar and 1000 ppm salt or 50 ppm of dye solution). After exposure at 12,000 ppm∙h of active chlorine, the flux of TFCCHD was enhanced with maintained high dye rejection. Therefore, the TFCCHD membrane has a potential application for dye desalination process.

High Flux Nanofiltration Membranes with Double-Walled Carbon Nanotube (DWCNT) as the Interlayer

“…Zeta potential is used to characterize the electric charge on the membrane surface [ 21 ]. The variation trend of membranes’ zeta potential for different DWCNT dosages is shown in Figure 5 .…”

“…As a kind of pressure-driven membrane separation technology [ 6 ], nanofiltration (NF) with high permeability and selectivity for specific components has developed rapidly in recent years. Until now, NF has been widely applied in water treatment [ 7 , 8 , 9 , 10 , 11 , 12 ], biomedicine [ 9 , 13 ], food [ 14 , 15 , 16 , 17 ] and environmental protection [ 18 , 19 , 20 , 21 ]. The preparation methods of NF membranes mainly include phase-transformation [ 22 ], surface coating [ 23 ], layer-by-layer self-assembly [ 24 ], surface grafting [ 25 ], co-extrusion [ 26 ] and interfacial polymerization [ 27 ].…”

Enhancing Performance of Thin-Film Nanocomposite Membranes by Embedding in Situ Silica Nanoparticles

“…The peak at 2241 cm −1 of hPAN corresponds with stretching vibration of CN bands, whereas the peak at 1735 cm −1 is attributed to CO stretching bands. As a result of interfacial polymerization between CHDA (with APTMOS) and TMC, a polyamide layer was formed on top of the hPAN support, and its formation is evidenced by the appearance of strong peaks of amide I and amide II at 1641 and 1556 cm −1 , respectively [32]. The peak at 1391 cm −1 of TFN is attributed to CH 2 vibration of APTMOS, and changes in the peak around 1102-1041 cm −1 (Figure 2b) suggest the embedment of silica coming from the Si-O-Si chain [33].…”