A critical review of membrane modification techniques for fouling and biofouling control in pressure-driven membrane processes

Abstract

The demand for new water resources has been increasing worldwide due to the growing global population and industrialization. Membranes play a central role in water purification processes with continuous technology improvements, new uses and cost reductions. Phase inversion is the most commonly used technique for preparing polymeric membranes. However, most commercial membranes are prepared from hydrophobic materials, which make them more susceptible to suffer the adsorption or deposition of molecules over their surface or inside their pores. This phenomenon, commonly termed as fouling, is one of the major operational problems in membrane processes. This review covers different membranes modification techniques to enhance permeability and to reduce fouling and the accumulation of microorganisms on membrane surface. The physicochemical properties of membrane surface can be tuned by grafting or coating to introduce functionalities like hydrophilic moieties or charged groups. Blending hydrophilic additives into the casting solution is another approach to increase membrane hydrophilicity and to improve water filtration performance. This review summarises the variety of porous materials that have been used to introduce inorganic nanoparticles into the casting solution. Porous carriers are used to introduce antimicrobial metals by preserving nanoparticle stability. Additionally, organic compounds, especially dendritic structures, have attracted considerable interest due to their highly branched structure, and their large number of terminal functional groups, which can also be used to enhance membrane properties. This work reviews the modification and functionalization techniques recently proposed to improve permeability and durability of the membranes used in pressure-driven separations.