Desalination, 2nd Edition

Chapter 7Continuous Electrodeionization

Jonathan H. Wood and Joseph D. Gifford

Evoqua Water Technologies, LLC, Lowell, MA, USA

Abstract

Continuous Electrodeionization is a hybrid of two well-known processes, ion-exchange deionization and electrodialysis. It was developed to allow the production of deionized water without the use of the hazardous acid and caustic that is required to regenerate ion exchange resins. An electric field is used as the driving force to transfer ions from a feed stream through a selectively permeable ion-exchange membrane to a reject stream, while simultaneously splitting water to regenerate ion exchange resins and allow the removal of weakly ionized contaminants. This process was first commercialized in 1987 and is now used extensively worldwide in many industries, especially in the production of deionized water for pharmaceutical formulations, power generation and manufacture of microelectronics/semiconductor devices.

Keywords: Electrodeionization, EDI, Continuous Electrodeionization, CEDI, Filled-cell, Ultrapure water

7.1 Introduction

Electrodeionization (EDI) is a process that removes ionizable species from liquids using electrically active media and an electrical potential to effect ion transport. The electrically active media in EDI devices may function to alternately collect and discharge ionizable species, or to facilitate the transport of ions continuously by ionic or electronic substitution mechanisms. EDI devices may comprise media of permanent ...