Construction and Chlorine Resistance of Thiophene-Poly(ethyleneimine)-Based Dual-Functional Nanofiltration Membranes

Abstract

The demand to improve the chlorine resistance of polyamide (PA) membranes is escalated with greater amounts of chlorine-containing disinfectant being used in global water treatment during the COVID-19 pandemic. In this work, we designed thiophene-functionalized poly­(ethyleneimine) (TPEI) materials first and grafted them onto a conventional PA membrane to develop novel nanofiltration membranes (PEI-M, TPEI-1-M, TPEI-2-M). These membranes have dual-functionalized selective surfaces covered by hydrophilic amino groups and electron-rich thiophene moieties, which endow these membranes with superior chlorine resistance and improved separation performance. The modified membranes increase the rejection of MgCl2 from 86.5% of the nascent PA membrane (PA-M) to higher than 93.0% without sacrificing the membrane water permeability. More stable separation performance is achieved with all of the as-prepared membranes than PA-M after exposure to a 2000 ppm sodium hypochlorite solution. TPEI-2-M outperforms other membranes after being treated in a chlorination intensity of 16,000 ppm·h with the smallest flux loss and the highest MgCl2 rejection. This is mainly ascribed to the highest amount of amino and thiophene moieties on the TPEI-2-M surface. This study provides an effective protocol for developing novel PA-based nanofiltration membranes while demonstrating its superiority over current technologies with exceptional separation performance and antichlorine ability.

Interface Engineering of Microporous Polypropylene Membranes for Polyamide Thin-Film Composite Nanofiltration Membranes with Robust Structure and Superior Performance

“…Over the past years, recovery and reuse of water have become one of the main priorities of human beings owing to the global warming, severe water pollution, and increased demand for water resources. − Membrane-based separation techniques have received increased attention because of the high efficiency, low energy consumption, and modular design. , Nanofiltration membranes are capable of separating divalent salt ions, dyes, and most organic matters from water by the Donnan effect and pore size sieving, which have been extensively used in the fields of water softening and treatment of industrial effluent. − Among different types of nanofiltration membranes, polyamide (PA) thin-film composite (TFC) membranes have been widely used as commercialized nanofiltration membranes. , A PA-TFC membrane is composed of a PA selective layer and a polymeric porous substrate. The PA layer dominates the separation performance of the membranes and is usually synthesized by interfacial polymerization between diamine monomers such as piperazine (PIP) or m -phenylenediamine (MPD) in an aqueous solution and trimesoyl chloride (TMC) in an organic solution …”

Polyester Nanofiltration Membranes for Efficient Cations Separation

“…[16][17][18] For example, performance of polyamide Li + /Mg 2+ separation membranes prepared from polyethylen DOI: 10.1002/adma.202309406 imine (PEI) was significantly declined when they were treated by sodium hypochlorite (NaClO). [19,20] By contrast, polyester membranes highlight desirable chlorine resistance because the ester bonds in them are stable against oxidants such as NaClO, [16,21,22] and the past decade has seen vigorous interests in polyester membranes. Many hydroxyl monomers such as cyclodextrins, [23][24][25] carbohydrates, [21,26,27] polyphenols, [28][29][30] zwitterions [31][32][33] have been studied for membrane preparation.…”

“…[ 16–18 ] For example, performance of polyamide Li + /Mg 2+ separation membranes prepared from polyethylenimine (PEI) was significantly declined when they were treated by sodium hypochlorite (NaClO). [ 19,20 ]…”