Pervaporation of water from aqueous sulfuric acid at elevated temperatures using Nafion® membranes

The concentration of sulfuric acid by pervaporation has been studied using Nafion-112® and Nafion-117® membranes, which have been characterized in terms of flux, permeability, and separation factor at 100 and 120 °C. Feed acid concentrations investigated ranged from 40 to over 80 wt%. In general, water fluxes ranged from 100 to 8000 g/m2 h, depending on feed acid concentration and separation factors as high as 104 were observed. Membrane stability was probed using dynamic mechanical analysis that revealed an increase in the temperature at which the α transition is observed, which corresponds to the glass transition (Tg) of the hydrophilic domain, upon use, suggesting embrittlement of the polymer structure. Further studies showed that the embrittlement was due to an interaction with the acid and was not induced by the operating temperature.