Controlling the physiochemical properties of graphene oxide coatings for improved membrane distillation

Abstract

Membrane distillation (MD) is a promising solution for global water scarcity, particularly for high-salinity wastewater treatment. However, MD membranes face critical challenges such as wetting and fouling in practical applications, particularly for saline wastewater containing organic pollutants. Membrane surface properties are crucial to prevent their tendency to wet and foul, and strategies involving membrane coatings have been developed. However, conventional approaches often struggle because of conflicting requirements for hydrophobic and hydrophilic coatings to prevent wetting and fouling, respectively, making it difficult to achieve optimal performance. Exploring favorable membrane coating properties and their correlation with membrane performance is essential for enhancing MD effectiveness but remains underexplored because of the complexity of commonly used composite coating materials. In this study, we applied graphene oxide (GO) nanosheets as bare coating materials to examine the relationship between coating properties and MD performance. GO materials allow feasible control over coating structure and chemistry, enabling coating and performance adjustments. It was demonstrated that a continuous dense coating with moderate hydrophilicity can enhance the antiwetting and antifouling capabilities of a hydrophobic MD membrane without compromising permeance. Continuity and pore size are pivotal for the application of effective hydrophilic coatings in MD. This study provides insight into the design of coatings for MD membranes to enhance the effectiveness of sustainable processes.