Study On Structure And Performance Of New Polyamide Reverse Osmosis Membrane

Nowadays, reverse osmosis(RO) is an important seawater desalination technology. However, fouling and chlorination of conventional commercial aromatic polyamide RO membrane are the main obstacles for the RO technology application. A lot of researches are currently focusing on the development of antifouling and chlorine tolerant RO membranes. In this study, a novel Trimesoylamidoamine(TMAAM) monomer was designed and synthesized according to the mechanisms of fouling and chlorination of conventional polyamide membranes, and then it was used to fabricate four new polyamide membranes, and these membranes’ antifouling and chlorine tolerant properties were analyzed.First, TMAAM was synthesized by trimesoyl chloride(TMC) and1,3-diamino-2-propanol(DAP) as raw materials via three-step method including esterification, amidation and ester aminolysis reactions successively. The effects of methanol dosage, type and amount of the acid binding agent, and DAP dosage on the reactions were discussed. The reaction mechanism of ester aminolysis was also explored. The chemical structure of product TMAAM was identified via infrared spectra(IR),nuclear magnetic resonance(NMR) and high-resolution mass spectragraph(HRMS). This three-step method has some advantages including mild reaction conditions, easy operation, convenient post treatment and favorite reaction economy. The top total product yield of three reactions is 57%. The ideal synthetical conditions were 2.0~2.5 of the mole ratio of methol to TMC in the esterification reaction,triethylamine/DMF as composite acid binging agent and 5.0~5.8 of the mole ratio of DAP to intermediate in the ester aminolysis reaction.Then, the composite amine of DAP and TMAAM was used to react with TMC through interfacial polymerization to fabricate four new polyamide RO membranes including DAP-TMC, DAP/TMAAM-TMC,DAP-TMAAM-TMC and TMAAM-TMC membranes. The effects of monomer concentration, reaction time and curing temperature on the membrane performance were investigated. The structure of the active layer of the resulted membranes were characterized by using scanning electron microscopy(SEM), atomic force microscopy(AFM), attenuated total reflectance infrared(ATR-FTIR) and X-ray photoelectron spectroscopy(XPS). The antifouling and chlorine tolerant properties of the four membranes were analyzed by dynamic fouling experiment and exposure experiment to active chlorine. The results show that all the four new membrane DAP-TMC, DAP/TMAAM-TMC, DAP-TMAAM-TMC and TMAAM-TMC present relative better antifouling and chlorinetolerant properties than conventional MPD-TMC membrane.