Interfacially synthesized chlorine-resistant polyimide thin film composite (TFC) reverse osmosis (RO) membranes

Abstract

Chlorine-resistant polyimide thin film composite (TFC) RO membranes were prepared via interfacial polymerization of m-phenylene diamine (MPD) and 1,2,4,5-benzene tetracarbonyl chloride (BTC) and subsequent thermal imidization. Thermogravimetric analysis, differential scanning calorimetry and attenuated total reflection-Fourier transform infrared spectroscopy confirmed that the use of a tertiary amine catalyst allowed the preparation of the polyimide films at below the glass transition temperature of the polysulfone support sublayer, thus preventing its degradation. The effects of annealing on the membranes performance were investigated. Increasing temperature and duration during the thermal treatment accelerated the imidization of the poly(amic acid) membranes and converted their amorphous structures to semi-crystalline structures, deteriorating their performance. The addition of a cross-linking agent, trimesoyl chloride (TMC), during the interfacial polymerization improved the membrane's performance. The polyimide thin film composite, reverse osmosis membranes prepared from MPD, BTC and TMC showed significantly enhanced chlorine resistance due to the elimination of chlorine-sensitive sites by the replacement of amide linkage with imide linkage.