Mixed matrix membrane incorporated with large pore size halloysite nanotubes (HNTs) as filler for gas separation: Morphological diagram

This study investigated the expected morphologies for MMMs comprising large pore size fillers. Halloysite nanotube (HNT) was employed as a representative of large pore size fillers to interpret the morphologies. It was expected that five main morphologies could be observed. The corresponding selectivity–permeability morphological diagram was proposed and compared to the morphological diagram proposed by Moore and Koros [3] for small pore size fillers MMMs. The proposed morphological diagrams were compared to a variety of experimental results from the open literature and the outcomes were in good agreements. This study addressed and confirmed that the type of filler (large or small pore size), type of membrane structure either dense symmetric or asymmetric and fillers particle size are among the most influential factors in determining the final MMMs separation performance.

• Five main expected morphologies for large pore size fillers embedded in MMMs were discussed.
• This study compliments to Moore and Koros study which covers a complete range of filler pore size.
• The diagram can play an important role to predict the relation of morphologies/MMMs performance.