Hexagonal Boron Nitride and Graphene Covalent Heterostructure to Resist Mineral Scale Formation and Organic Fouling in Membrane Distillation

Abstract

Two-dimensional hexagonal boron nitride (hBN) can act as the superior scaling resisting materials due to its unique structure, yet the application of hBN is hampered due to the tediousness and high cost of chemical vapor deposition (CVD) method. Here we report a simple and accessible method to fabricate a hBN/rGO heterostructure via polyelectrolyte assembly with extraordinary scaling and organic fouling resistance. The results demonstrated a notable 17.4% increase in pure water flux and a significant 92% reduction in scaling rate when the hBN/rGO-PVDF membrane was challenged with a saturated CaSO4 solution. In addition, the membrane also demonstrated a 57-80% reduction of organic fouling rate as compared to virgin PVDF membrane. Through the XDLVO theory and DFT calculations, we revealed that the interaction between hBN and water molecules is stronger than that of graphene. The unique electronic structure and polar interactions of hBN in hBN/rGO heterostructure endow it to form a stable hydration layer that acts as a formidable barrier against scaling and fouling. The extraordinary organic fouling resistance was also correlated to the formation of membrane surface energy barrier for the adsorption of HA and BSA. This study provides a new perspective for development of membranes with excellent scaling and fouling resistance, which can be used as a promising candidate for large-scale industrial membrane distillation applications.

Keywords: Membrane distillation hBN/rGO heterostructurePolyelectrolyte assemblyCaSO4 scalingOrganic fouling