Abstract
Alternative chemicals for the regenerant of ion exchangers have been the subject of research for the past sixty years. The advances spanning this time period have been significant and demonstrated at the laboratory, pilot, and commercial scale. The use of carbon dioxide as a regenerant has several significant benefits including cost savings, waste minimization, and carbon dioxide sequestration, with applications including: chemical synthesis, desalination, demineralization, metals removal and hardness removal. Having originally been pursued as a means of reducing costs of regenerant chemicals, regeneration with carbon dioxide has also been described as a non-polluting separation process and has shown significant environmental benefits. Its use as a regenerant circumvents the use of brines, strong acids, or other aggressive chemicals and with the advent of new materials such as ion exchange fibers, the list of potential applications will continue to grow. This review discusses some of the significant advances during the history of this environmentally benign regeneration process.