Impact of hPG molecular size on the separation properties and antifouling performance of hPG-modified thin-film composite nanofiltration membrane

Membrane fouling presents a critical barrier for the economic operation of nanofiltration (NF) membranes in large-scale applications. 3D hydrophilic hyperbranched polyglycerol (hPG) exhibited the distinctive properties of simultaneously enhancing the antifouling properties and separation performance of the membranes when grafted onto the thin-film composite (TFC) polyamide membranes. Three sizes of hPG (H1: 2076 g mol−1, H2: 4769 g mol−1, H3: 7440 g mol−1) were grafted onto the surface of the TFC NF membranes to comprehensively study the impact of hPG molecular size on the surface properties and antifouling performance of the hPG-grafted TFC NF membranes. Experimental results showed that two important parameters including the hPG surface coverage ratio and the hydration layer thickness of the membrane surface, rather than water contact angle, can well predict the tendency of the antifouling performance of the hPG-grafted membranes. Moreover, with the increasing size of hPG, both the hPG surface coverage ratio and the hydration layer thickness of the hPG-grafted membrane surface follow the same trend of TFC-H3 > TFC-H1 > TFC-H2, as did the membrane antifouling tendency. Thus, our work provides a new sight on the effect of the hyperbranched molecular size on the surface properties of the modified membrane to reveal the antifouling properties and mechanism of the modified membrane surface.