Electrochemical membrane separation of chlorine from gaseous hydrogen chloride waste

Hydrogen chloride is a gas-phase by-product of many manufacturing chlorination processes. Growing environmental concerns have prompted several techniques for converting hydrogen chloride to elemental chlorine for recycling. A novel electrochemical membrane process has been developed for the recovery of chlorine from gaseous hydrogen chloride waste. Hydrogen chloride is reduced at the cell cathode, producing hydrogen gas and chloride ions. The chloride ions migrate across the molten salt electrolyte-saturated membrane to the anode where chlorine is evolved by oxidation. Experiments began with free electrolyte trials in the absence of a membrane separator and were followed by a single membrane cell study. Preliminary studies show that electrochemical membrane separation is a feasible alternative for the removal of chlorine from hydrogen chloride. The results indicate that chlorine can be effectively removed from a hydrogen chloride gas mixture at reasonable voltages, resulting in a high conversion efficiency. The proposed system offers advantages over conventional means such as on-site chlorine recycling in a single-step and on a continuous basis. (C) 1999 Elsevier Science B.V.