Enhancement of membrane distillation performance by porous organic and inorganic materials: a state-of-the-art review

Membrane distillation (MD) is an attractive thermally driven separation process due to its efficiency to treat highly concentrated feed streams in desalination and different industrial applications. Usually, hydrophobic microfiltration membranes are employed in MD process; however, conventional MD membranes possess rather low permeating flux and are prone to fouling. As a result, MD has not been widely adopted for water treatment and separation purposes at large commercial scale yet. Hence, development of novel MD membranes with enhanced properties is an important task. One of the main approaches to adjust porous structure and properties of MD membranes is through incorporation of different additives in membrane matrix. For the first time, the present paper overviews the use of porous organic and inorganic materials with controlled pore size such as metal organic frameworks, covalent organic frameworks, halloysites, zeolites and carbon nanotubes for enhancing properties and separation performance of MD membranes. While the employing of some of these materials in MD membranes looks promising, there are some issues that need to be addressed such as fabrication costs of such porous materials, stability of the additive’s incorporation in the membrane matrix and lack of long-term testing of the prepared MD membranes with real feed streams. The future work should also focus on the development of affordable and less complex techniques for preparation of MD membranes incorporated with porous organic and inorganic materials to compete with the fabrication of conventional MD membranes.