Preparation of high-flux zeolite T membranes using reusable macroporous stainless steel supports in fluoride media

Zeolite T membranes were prepared using the macroporous stainless steel and mullite tubular supports in fluoride media. The microstructures (orientation and membrane thickness) and separation performance of supported zeolite T layers were strongly affected by the supports, fluoride salts and synthesis temperature and time. Six membranes prepared on macroporous stainless steel supports showed a high average flux of 6.7kgm^-2h^-1 and a high average selectivity of 5300 with low deviations for a 90wt% isopropanol solution at 348K. Due to the thinner zeolite layers and lower resistance of the support layer, the flux of stainless steel supported zeolite T membranes was 50% higher than that of mullite supported zeolite T membranes. The used stainless steel support for membrane synthesis was effectively refreshed after a cleaning process in a 6mol l^-1 NaOH solution at 383K. The membrane prepared on the 2-time-reused stainless steel support showed comparable separation performance with the fresh membrane, suggesting that the stainless steel supports had a good reuse prospect for zeolite T membrane preparation. The location of fluorine in zeolite framework and the effect of fluoride salts were also demonstrated.