Gypsum Scaling Behavior of the Tannic Acid-Coated Polyamide Reverse Osmosis Membrane

Tannic acid modification on reverse osmosis (RO) polyamide membranes was explored, and its influence on controlling membrane gypsum scaling was first investigated. Tannic acid was chosen due to its unique properties, such as its ability to bond with metal centers, create hydrogen bonds, and interact hydrophobically. The presence of tannic acid was found to not effectively prevent gypsum scaling despite the enhancement of wettability after modification. The ability of tannic acid to chelate with Ca2+ ions can also exacerbate gypsum formation on the membrane surface. Nonetheless, the study suggests that tannic acid-coated membranes show approximately 100% flux recovery after physical cleaning, indicating that the coating's strong hydration layer easily removes the scalant during cleaning. Upon investigation of the presence of other metal centers, such as Fe3+, it was found that the interactions between tannic acid, Fe3+, and gypsum may have complex and unexpected consequences on the membrane performance. Overall, this study could contribute valuable insights into the applications of tannic acid in membrane technology, highlighting both its benefits and limitations in the context of fouling and scaling resistance. Further investigations and innovative approaches are necessary to fully exploit the potential of tannic acid modification for the development of advanced RO membranes.