Supported MFI zeolite membranes by cross flow filtration for water treatment

In the last years, intense research efforts were dedicated to the development of zeolite membranes in different separation processes. In this work, zeolite membranes were prepared and characterized by means of single gas and pure water permeation test. Moreover, the membranes performance in vacuum membrane distillation was also studied to determine their potentiality for desalination. Uncalcined defect free MFI (silicalite) membranes on different tubular supports were synthesized by using the secondary growth method coupled with the cross flow seeding procedure. Gas permeation tests showed that, using a support with pore size of 70 nm and a zeolite slurry concentration of 0.032 wt.%, uncalcined defect free MFI membranes were synthesized. To seal the defects formed after the calcination, two different curing treatments, new cross flow filtration with small crystals and dip coating with PDMS, were carried out. Very low defects concentration for the membranes cured with small crystals was evidenced in pure water permeation tests. In fact, permeance values in the nanofiltration range were obtained. Furthermore, these zeolite membranes were used in vacuum membrane distillation tests with promising results in terms of fluxes and salt rejections.