Polyamide thin film composite membranes prepared from isomeric biphenyl tetraacyl chloride and m-phenylenediamine

Three novel of isomeric tetra-functional biphenyl acid chloride: 3,3′,5,5′-biphenyl tetraacyl chloride (mm-BTEC), 2,2′,4,4′-biphenyl tetraacyl chloride (om-BTEC), and 2,2′,5,5′-biphenyl tetraacyl chloride (op-BTEC) were synthesized, and used as new monomers for the preparation of the thin film composite (TFC) reverse osmosis (RO) membranes through interfacial polymerization with m-phenylenediamine (MPDA). The results of membrane performance test showed that membranes prepared from om-BTEC and op-BTEC had higher flux at the expanse of rejection compared with membranes prepared from mm-BTEC. The chemical composition on the active layer was characterized by attenuated total reflectance infrared (ATR-IR) and X-ray photoelectronic spectroscopy (XPS), and the results showed that the content of carboxylic acid on the membrane surface prepared from mm-BTEC are higher than these prepared from op-BTEC and om-BTEC. It seemed that all the difference containing: the membrane performance, the chemical composition on the active layer, hydrophilicity, and the surface morphology might come from the different structure and reactivity of the tetraacyl chloride monomers.