Recovery of hydrochloric acid from metal pickling solutions by membrane distillation

Membrane distillation (MD) was applied for the concentration of solutions containing hydrochloric acid and salts. It was found that under MD conditions through pores of a hydrophobic membrane both water vapor and hydrogen chloride are transported. This effect wits utilized for the recovery of HCl from acidic spent solutions. The experiments were performed using model or real metal pickling solutions with different compositions. Two methods of the feed concentration for the acid recovery were proposed. The results of the studies show that MD may be a promising method for HCl recovery from industrial effluent. (C) 2001 Elsevier Science B.V. All rights reserved.