The concentration of hydriodic and sulfuric acid aqueous solutions by membrane distillation (MD) was experimentally investigated. Two commercial hydrophobic membranes, with two different recirculation batch configurations, were tested: direct contact membrane distillation (DCMD) with a polypropylene (PP) capillary membrane, and air-gap membrane distillation (AGMD) with polytetrafluoroethylene (PTFE) flat-sheet membrane. Feed temperatures were 58°C for DCMD and 80°C for AGMD, with cooling water at 15°C and 1atm operating pressure in both cases. H2SO4 concentration in the feed solution increased from 1.1 up to 7.0mol/L with the DCMD and from 0.9 up to 10.1mol/L with the AGMD. HI concentration increased from 0.3 up to 7.0mol/L with the DCMD and from 0.3 up to 8.0mol/L with the AGMD. The latter value is higher than the azeotropic concentration of the HI/H2O (7.57mol/L) mixture and, hence, HI further separation from water can be easily achieved with conventional distillation units. Durability of PTFE membrane in acid solutions was assessed too.