Pervaporation of water/ethanol mixtures through polyimide based mixed matrix membranes containing ZIF-8, ordered mesoporous silica and ZIF-8-silica core-shell spheres

Abstract

BACKGROUND: Pervaporation (PV) is a prospective industrial process for the separation of liquid mixtures such as azeotropic and close-boiling point. PV efficiency depends mainly on the properties of the membrane used. Hence, designing a membrane structure with high permeation rate and separation factor is an important issue. RESULTS: Mixed matrix membranes (MMMs) containing a number of molecular sieves, i.e. metal organic framework ZIF-8, ordered mesoporous MCM-41 silica spheres of two sizes, 3.1μm (MSS-1) and 0.53μm (MSS-2), and ordered mesoporous silica-(ZIF-8) core-shell spheres (MSS-Z8), were prepared at different filler loadings using polyimide (PI) Matrimid® 5218 as polymeric matrix and applied in the dehydration of ethanol via PV. With MSS-2 MMMs the PV flux was improved from 0.24 to 0.44kgm-2h-1 without significant changes in the separation factor compared with the bare PI membrane. CONCLUSIONS: PV performance of the PI membrane was improved by adding different fillers to the polymer matrix, and the effect of porosity, hydrophilicity and particle size of the filler on the PV results was analyzed. The best result in terms of PV performance was obtained with 12wt% MSS-2 MMM, where the use of smaller particles yielded a superior particle-polymer interfacial area and provided better accessibility to the hydrophilic silica pores.