Scale-up of MFI zeolite membranes for desalination by vacuum membrane distillation

Zeolite membranes represent a potential alternative to the polymeric ones for water desalination because of their high chemical stability and their peculiar ability to reject ions. In this work, supported zeolite membranes having Mordenite Framework Inverted (MFI) topology were scaledup and membranes 30 cm long were prepared using the secondary growth method coupled with the cross flow seeding procedure. In particular, the influence of rotation time during the seeding procedure was evaluated. The prepared membranes were characterized by scanning electron microscope (SEM), X-ray diffractometry (XRD), Energy Dispersive X-ray (EDX) analysis and single gas permeation, and then underwent to Vacuum Membrane Distillation (VMD) tests using both deionized water and NaCl solutions at different concentrations. The experimental work allowed to identify the membrane able to provide interesting trans-membrane flux and salt rejection values. Specifically, permeate fluxes of 13.8kg m-2 h-1 and 8.2 kg m-2 h-1, together with rejections of 99.8% and 99.6%, were achieved for the 0.2 M and 0.9 M feeds, respectively. No changes in the membrane structure after the exposure to salty solutions were detected by SEM and XRD analyses and its original performance was restored by means of an identified cleaning procedure