Effect of heat treatment on performance of chlorine-resistant polyamide reverse osmosis membranes

In our series of studies for the development of a reverse osmosis polyamide membrane with high resistance to chlorine, N,N′-dimethyl-m-phenylenediamine (N,N′-DMMPD) was selected in the preparation of the polyamide membrane after the screening of various diamines. High resistance to chlorine was confirmed for the prepared membrane in our previous work. However, the heat treatment conditions were not yet optimized. In this work, we focused on the effects of heat treatment conditions on the membrane properties. The heat treatment temperature and time remarkably influenced salt rejection and flux. Maximum rejection was found with respect to the temperature. Both rejection and flux showed trends to become constant with longer treatment times. However, rejection reached the constant value in less time than flux. Thus, to obtain both high rejection and flux, an optimum treatment time existed. The newly prepared polyamide membrane showed higher salt rejection than the previously prepared membrane while maintaining high resistance to chlorine.