Novel insights into the interplay between support and active layer in the thin film composite polyamide membranes

Abstract

Fundamental problems in thin film composite (TFC) reverse osmosis (RO) membranes in terms of the interfacial adhesion between the support and the active layer, the impact of support surface pore characteristics on the active layer formation process and the accordingly obtained active layer properties were investigated. Paper studies mainly includes following aspects: Five types of polysulfone (PSf) supports with varied surface pore characteristic properties were prepared and characterized; Thin film composite (TFC) polyamide (PA) reverse osmosis (RO) membranes were fabricated on these supports via in situ interfacial polymerization (IP) technology under identical IP protocols, and the performance and properties of the obtained TFC membranes were investigated systematically; Three types of these supports produced TFC membranes with both good salt rejection and high water flux. On the other hand, two types of them produced TFC membranes with inferior salt rejection attributed to the delaminated active layer from the support; The root cause for the delamination was explored and a speculated mechanism model for it and for the impact of support surface pore characteristic on the active layer formation was proposed. Furthermore, profilometer was used for the first time to measure the accurate thickness of individual active layer to overcome the shortcomings of the conventional electron microscope technologies. The basic understanding of the interplay between the support and the active layer provides important information for developing of thin film composite (TFC) membranes with improved performance.