Fig. 9: Elemental mapping for Si (b), Al (c), and O (d) of the cross-section, and the Si/Al ratio of the membrane surface (e) of the M14 sample prepared in this work by EDAX spectrum quantification technique
The EDX elemental mapping for Si, Al, and O of the cross-section and the Si/Al ratios of the surface of the best ZSM-5 zeolite membrane prepared in this work (M14 membrane) are shown in Fig. 9. It can be found from Fig. 9 that the Si/Al ratio of the membrane surface reached 50, reflecting that despite the low Si/Al ratio of initial synthesis solution (⁓160) a part of the alumina from the support (as aluminate ions) dissolves in the synthesis solution and is incorporated into the framework of zeolite layer during the secondary growth method [22]. Nevertheless, as it is well known that the hydrophilicity of a zeolite membrane strongly depends on the Si/Al ratio of zeolite layer, the ZSM-5 membranes prepared in this work still could be used for organic/water separation process by pervaporation technique.