ELECTROTRANSPORT OF SULFURIC-ACID IN SPECIAL ANION-EXCHANGE MEMBRANESFOR THE RECOVERY OF ACIDS

The transport properties of anion exchange membranes specially designe d for the recovery of acids by electrodialysis were studied using aque ous H2SO4 solutions. When the membranes were not submitted to any driv ing force, measurements of sorption, water content, self-diffusion flu x, electrical conductivity and results of Raman spectroscopy showed th at the membranes cannot be accounted for by a classical gel-phase mode l and, on the other hand, that only HSO4- ions balanced the exchanging sites. The apparent mobilities of these ions and of SO42- ions in the interstitial region were also determined. When the membranes were sub mitted to an electrical field, measurements of unidirectional fluxes b y the radiotracer technique showed that, even for diluted H2SO4 soluti ons, the value of the transport number of SO42- ions never exceeded 0. 85 for the membranes bearing weak basic exchanging groups while it rea ched unity for the membrane bearing strong basic exchange groups. This phenomenon was attributed to proton transfer reaction between exchang ing groups and HSO4- ions. This reaction favored the proton leakage. F or higher H2SO4 concentrations the membranes bearing weak basic groups presented a reduced proton leakage.