Correlation between barrier layer Tg and a thin-film composite polyamide membraneʹs performance: Effect of chlorine treatment

In this study we report changes in the glass transition temperature (Tg) of the polyamide barrier layer (PBL) of a commercial RO membrane as a function of chlorine treatment in which concentration and pH were systematically varied. The results indicate a monotonic decrease of Tg with increasing exposure time at a given chlorine concentration. Further, both the degree and the rate of Tg decrease vary significantly with both the chlorine concentration and pH value of the aqueous chlorine solution. Moreover, the decrease in PBL Tg correlates well with the reduction in the salt rejection of the membrane, but the magnitude of the correlation is specific to chlorine concentration and pH values.