Thin-film composite polyamide membrane modified by embedding functionalized boron nitride nanosheets for reverse osmosis

Modifying polyamide membranes with nanomaterials has proven effective for enhancing water flux and salt rejection and membrane resistance against fouling and chlorine. In this study, we prepared a novel thin-film nanocomposite reverse osmosis membrane by embedding functionalized boron nitride nanosheets (FBNS) into the polyamide layer via in situ interfacial polymerization process. As a result of the incorporation of FBNS, the expansion of homogeneous leaf-like structure of the polyamide layer, as indicated by the increased surface roughness as well as the thinner and more hydrophilic active layer, enhances the water permeance of membrane by 25% to 4.0 LMH/bar while maintaining a high salt rejection of 96.4%. The FBNS incorporated nanocomposite membranes also demonstrate improved chlorine resistance and performance stability under various stress test conditions when comparing to the pristine membrane. The humic acid fouling test indicates that the modified membrane has a flux recovery of over 96% after one cleaning cycle. This work provides new insights into the effect of boron nitride nanosheets on membrane network structures and separation performance and provides a scalable membrane improvement strategy based on emerging 2D nanosheets.