The chlorination process of crosslinked aromatic polyamide reverse osmosis membrane: New insights from the study of self-made membrane

The development of chlorine-resistant membranes requires good understanding of membrane chlorination process. However, researches involving membrane chlorination processes are often influenced by experimental materials, especially the commercial crosslinked aromatic polyamide RO membranes, the preparation or modification technology and composition of which are not fully disclosed. In this work, the changes in membrane chemical structure and composition during the chlorination process were systematically studied by the use of self-made crosslinked aromatic polyamide RO membranes to avoid these influences. The effects of different chlorination conditions and pure water immersion time were analyzed. For the first time, the reversibility of the chlorination process was investigated. The ATR-FTIR and XPS results indicated that chlorination involves a multi-step process. The IR bands which characterize the amide groups (1540 and 1608 cm− 1) gradually disappear, followed by the appearance of the bands which characterize the chlorination of aromatic ring (780 and 811 cm− 1). The increase rates of the chlorine content are different at different stages. The changes in chemical structure and composition of self-made membrane were compared with those of two representative commercial membranes (RE2521 and BW30). Furthermore, the consequential effects of these changes on surface hydrophilicity, charge, permselectivity performance, and morphology of self-made membrane were discussed.

► Self-made aromatic polyamide membrane was used to study chlorination process.
► The reversibility of chlorination of aromatic polyamide was first investigated.
► A multi-step process of aromatic polyamide membrane chlorination was confirmed.
► A comparison of self-made and commercial membranes chlorination was performed.