Ion exchange resin blended membrane: Enhanced water transfer and retained salt rejection for forward osmosis

To improve the efficiency of forward osmosis (FO) process, Na type ion exchange resin (IER-Na) powders were successfully blended into the support layer of FO membrane, which could introduce extra charged passageway. Consequently, the water flux of 5wt%IER-Na (with 5 wt% IER-Na loading) was 1.75 times as large as that of 0wt%IER-Na (with 0 wt% IER-Na loading), under the condition for evaluating FO performance (1.5 mol/L NaCl as draw solution and de-ionized water as feed solution in AL-DS mode). Notably, the salt rejection was retained above 95.0%. By multi-techniques such as SEM, EDS, ATR-FTIR and the analysis of diffusion coefficients in both polysulfone and IER-Na, it was proved that the enhanced water flux was mainly attributed to the extra charged passageway introduced by IER-Na. Meanwhile, the retained salt rejection was ascribed to the considerable salt rejection of extra charged passageway in IER-Na. This work sheds light on a new perspective in promoting the mass transfer in FO membranes.