Protein-Decorated\nReverse Osmosis Membranes with High\nGypsum Scaling Resistance

The global challenge of water scarcity has fueled significant\ninterest\nin membrane desalination, particularly reverse osmosis (RO), for producing\nfresh water from various unconventional sources. However, mineral\nscaling remains a critical issue that compromises the membrane efficiency\nand lifespan. This study explores the use of naturally occurring proteins\nto develop scaling-resistant RO membranes through an eco-friendly\nmodification method. We systematically evaluate three protein modification\ntechniques, namely, polydopamine (PDA)-assisted coating, protein conditioning,\nand protein drying, for fabricating membranes resistant to gypsum\nscaling. Protein conditioning is found to be the most effective approach,\nresulting in protein-decorated membranes with an exceptional resistance\nto gypsum scaling. We also demonstrate that a hydrated protein layer\nis essential for optimal scaling resistance. To further understand\nthe mechanism underlying the scaling resistance of protein-decorated\nmembranes, five proteins (i.e., bovine serum albumin, casein, lactalbumin,\nlysozyme, and protamine) with distinct physicochemical properties\nare used to explore the key factors governing membrane scaling resistance.\nThe results of dynamic RO experiments indicate that the molecular\nweight of proteins plays a crucial role, with higher molecular weights\nleading to higher membrane scaling resistance through steric effects.\nHowever, static experiments of bulk crystallization highlight the\nimportance of electrostatic interactions, where proteins with more\nnegative charge delay gypsum crystallization more effectively. These\nfindings suggest the difference between gypsum scaling in the RO and\ngypsum crystallization in bulk solutions. Overall, this research offers\na novel approach to developing resilient and sustainable RO membranes\nfor the desalination of feedwater with high scaling potential while\nelucidating mechanistic insights on the mitigating effects of protein\non gypsum scaling.