Separation of HCl from HCl–H2SO4 solutions by membrane distillation

Hydrochloric acid is a volatile compound; thus it can be separated from its solutions by membrane distillation (MD). The feed solutions consisted of a mixture of hydrochloric and sulphuric acids with various initial concentrations.It was found that duringMDprocess the sulphuric acid was completely retained in the feed, thus its concentration was gradually increasing, whereas hydrochloric acid solutions were concentrated at low concentrations. At higher con-centration of both acids in the feed, HCl was separated from the mixture under the process conditions. For HCl concentration in the feeding solution equal to 51.72 g/m3 along with an increase in the H2SO4 concentration from 50 to 150 g/m3, the molar HCl flux increased from 2.27 to 20.12 mol/m2d at 333K and from 31.22 to 80.12 mol/m2d at 343 K.During the concentration of solution with an initial concentration of 51 g/m3 of HCl and 51 g/m3 H2SO4 at the feed temperature 333K the permeate flux decreased from 225 to 158 dm3/m2d. An increase in the initial concentration of sulphuric acid to a value of 180 g/m3 in the feed decreased the permeate flux from 202 to 135 dm3/m2d.