Mass transfer of HCl and H2O across the hydrophobic membrane during membrane distillation

The studies on water vapour and HCl transfer through the hydrophobic membra ne during membrane distillation (MD) have been performed. The flat-sheet me mbranes made from polyretrafluoroethylene (PTFE) or poly(vinylidene fluorid e) (PVDF) and polypropylene (PP) capillary membrane were used in the experi ments. The performance of the applied membranes has been compared. It was f ound that the course of the concentration of hydrochloric solution was diff erent as a consequence of the various membrane morphologies. However, for a ll membranes used, the final level of HCl concentration in the feed amounti ng 253 g HCl/dm(3) (T-F = 343 K) was achieved. It has been shown that durin g the concentration of HCl solutions by MD, the HCl content in the permeate may be higher than in the feed. A beneficial effect of salt in the feed on the separation of HCl from the solution has been demonstrated. Analysis of mass transport across the membranes was performed, taking into account a multicomponent diffusion through the stagnant air layer existing inside the pores of the membranes. The agreement between the results theore tically predicted and the experimental data was satisfactory. (C) 2000 Else vier Science B.V. All rights reserved.