Modification of a polyamide reverse osmosis membrane by heat treatment for enhanced fouling resistance

The use of heat treatment to improve solute rejection and fouling resistance of a polyamide reverse osmosis (RO) membrane was investigated in this study. Heat treatment was carried out by immersing the membrane samples in Milli-Q water at 70 degrees celcius for a specific duration. Heat treatment reduced the pure water permeability from 4.1 to 2.8 L/m2 bar but improved conductivity rejection from 95.5 to 97.0 percent. As a result, a correlation was observed between changes in the two parameters. Marginal changes in the membrane surface characteristics were observed as a result of heat treatment. Heat treatment significantly improved the fouling resistance property of the RO membrane. When the secondary effluent was filtrated at an elevated permeated flux, the virgin RO membrane exhibited 30 percent flux decline while the heat-treated membrane showed only 12 percent flux decline. This is possibly because heat treatment resulted in a denser cross-linked active skin layer, thus reducing the blockage caused by small organic foulants.