Critical review of montmorillonite/polymer mixed-matrix filtration membranes: Possibilities and challenges

Abstract

This paper reviews the literature on clay/polymer (CP) based mixed-matrix membranes (MMM) for water treatment. Clay minerals have been credited for ultrafiltration (UF) membranes behaving like nanofiltration (NF) membranes in terms of salt rejection through the repulsion mechanism. This is interesting and more attention should be focused on this approach. There is an apparent agreement in the literature that the observed increase and then decrease in water flux with an increase in clay mineral loading is a result of viscosity changes in the casting solution. While this is true, there is still a need for studies that will consider that the clay mineral sheets are much larger compared to water molecules and are impermeable; hence, at higher loading they may impede water flow. Exfoliated clay platelets are basically similar to graphene oxide, which has gained significant attention lately in water treatment studies; however, to date, there is no information on the effect of the delaminated structures on the performance of available CP membranes.