Preparation Of Aromatic Polyamide Nanofitration Membranes With Improved Chlorine Resistance

Aromatic polyamide nanofiltration(NF) membranes are easy to be attacked by the active chlorine, which leads to a decline in the separation performance of polyamide NF membranes. This issue was taken as the research point. Bis-2,6-N, N-(2-hydroxyethyl) diaminotoluene and trimesoyl chloride (TMC) were chosen as the monomer polymer materials. The polymerization was reacting on the polyether sulfone (PES) ultrafiltration(UF) support film based on interfacial polymerization. A kind of polyamide NF composite membrane was successfully fabricated after curing at vacuum for a while. Polyamide NF membrane had a better chlorine resistance as well as high rate of desalination, large water flux and high mechanical strength, etc. Therefore, it can be predicted that the polyamide NF membranes with improved chlorine resistance will have broad applications in the pharmaceutical industry, water treatment, chemistry, biochemistry and electronics and other fields.The chemical composition, structure and morphology of polyamide NF membranes were characterized by Fourier transform attenuated total reflection infrared spectrometry (ATR-FTIR), atomic force microscope (AFM), scanning electron microscope (SEM) and contact angle measurement techniques. Results showed that the polyamide NF membranes were successfully fabricated in the experiments. The composite membrane surface roughness is higher than that of the support film. The cross-section surface had obvious finger and pore structure. Composite membrane was mainly composed by the interception effect of polyamide separation layer and the PES support film. In addition, the hydrophilic of polyamide NF membrane had been higher improved.Polyamide NF membranes before and after immersed in200mg·L-1NaClO solution were analyzed in the plat membrane separation equipment. The concentration of MgSO4or NaCl used in the experiments was2g·L-1. The rejections of MgSO4and NaCl were95.5%and58.37%, respectively. And the water fluxes were32.20L·m-2h-1and47.75L·m-2·h-1. The results showed that polyamide NF membranes had good resistance to chlorine. Soaked in200mg·L-1NaClO solution for50hours, polyamide NF membranes performed a high level of the rejection of MgSO4.In this thesis, the chlorination of fabricated aromatic polyamide NF membrane in the experiments could also indirectly indicate that the possible chlorination mechanism of polyamide composite membranes. According to the period order of chlorination, the possible chlorination process of polyamide composite membranes is:(1) the amine’s chlorination of the polyamide;(2) the aromatic ring’s chlorination aroused by orton rearrangement;(3) the rupture of polyamide chains.