Non-solvent induced phase inversion strategy enables scaling resistance without post-modification for membrane distillation application

At high salinities, scaling of hydrophobic membranes by sparingly soluble salts causes flux decline and eventual membrane failure in membrane distillation (MD) technology. To overcome this, a large body of research has focused on chemically modifying existing hydrophobic membranes. While chemical modification of polyvinylidene-difluoride (PVDF) membranes by fluoroalkyl silanes improves resistance to mineral scaling, it involves multiple steps, harsh chemicals, and offers only marginal improvement. In this study, we present the possibility of engineering anti-scaling surfaces by tailoring the top membrane layer during non-solvent-induced phase separation (NIPS) itself. Contrary to common perception where scaling resistance mandates a rough superhydrophobic surface, our comparative studies reveal that PVDF membranes with a relatively smooth surface and low pore size effectively deter gypsum scale adhesion over other NIPS strategies. The same also outperformed commercial PVDF membranes of different average pore sizes (0.45 µm and 0.2 µm). Overall, while NIPS can be tailored to fabricate PVDF membranes with diverse morphologies, our findings demonstrate that using water as the non-solvent yields a membrane surface on which gypsum scales exhibit weak adhesion, allowing most deposits to be readily washed away.