Recent progress in the hydrophilic modification of alumina membranes for protein separation and purification

In general, alumina membranes have been extensively developed for protein separation and purification. Alumina membranes, which naturally feature a moderate hydrophilic character (contact angle of 40-50 degrees) and the lowest cost among other oxide materials, are most suitable for these applications. Membrane fouling occurs due to the deposition and adsorption of proteins on the surface and pore walls of alumina membranes. This is one of the major issues that prevent the applicability of alumina membranes. Therefore, it is important to minimise membrane fouling by enhancing the hydrophilic character of the membranes as well as reducing interactions between proteins and the membranes surface. This review discusses the surface modification of alumina membranes in an effort to enhance the hydrophilic character of the membranes. Moreover, the introduction of graphene derivatives in modifying the hydrophilicity of alumina is also addressed. The superhydrophilic character of the alumina surface has a major influence on its anti-fouling and permeate flux properties, thus it improves the performance of the protein separation and purification processes.