Influence of acid on the permeation properties of NaA-type zeolite membranes

The acid stability of the NaA-type zeolite membrane was evaluated in this study. For the rapid evaluation of membrane stability, the change in the permeation fluxes of the membrane was monitored in real-time by using a mass spectrometer during pervaporation. When sulfuric acid was added to the feed solution, the permeation flux of water decreased dramatically immediately after the acid addition (step (I)), then decreased slightly (step (II)), and finally increased significantly (step (III)). The permeation flux of ethanol also increased significantly in step (III). As a result, the NaA-type zeolite membrane lost its separation ability for an equimolar mixture of water and ethanol at 313 K in 10 min after the addition of 1.0 mL sulfuric acid. Hydrolysis reaction and dissolution occurred in steps (I)–(III). Furthermore, we also discuss the influence of the amount of added acid and ethanol content of the feed solution on the destruction of the zeolite membrane.