THE INFLUENCE OF SALT IN SOLUTIONS ON HYDROCHLORIC-ACID RECOVERY BY MEMBRANE DISTILLATION

The concentration and recovery of HCl by membrane distillation (MD) wa s performed in a capillary module with polypropylene membranes. The in fluence of acid concentration and salt presence in the feed on HCl mol ar flux through the membrane was systematically studied. The feed temp erature was kept at 333 or 343 K, and the permeate temperature at 293 K. The studies show that for a low HCl content in the feed, the permea te was practically pure water. The increase of temperature and acid co ncentration in the feed caused a substantial increase in HCl molar Aux through the membrane. The presence of FeCl3 in the feed and the incre ase of its concentration in the feed causes a significant increase in HCl molar flux in comparison with the case of pure acid. Because the s alt was retained in the feed, the permeate was pure hydrochloric acid with increasing concentration. The experiments were also performed wit h a real pickle solution. The results show that MD can be applied for the recovery of hydrochloric acid from the acidic industrial effluents . (C) 1998 Elsevier Science B.V. All rights reserved.