title: Investigation on removal of hardness ions by capacitive deionization (CDI) for water softening applications.
abstract: Capacitive deionization (CDI) for removal of water hardness was investigated for water softening applications. In order to examine the wettability and pore structure of the activated carbon cloth and composites electrodes, surface morphological and electrochemical characteristics were observed. The highly wettable electrode surface exhibited faster adsorption/desorption of ions in a continuous treatment system. In addition, the stack as well as unit cell operations were performed to investigate preferential removal of the hardness ions, showing higher selectivity of divalent ions rather than that of the monovalent ion. Interestingly, competitive substitution was observed in which the adsorbed Na ions were replaced by more strongly adsorptive Ca and Mg ions. The preferential removal of divalent ions was explained in terms of ion selectivity and pore characteristics in electrodes. Finally, optimal pore size and structure of carbon electrodes for efficient removal of divalent ions were extensively discussed.
authors.affiliation: Department of Environmental Science and Engineering, Gwangju Institute of Science and Technology (GIST), 261 Cheomdan-gwagiro, Buk-gu, Gwangju 500-712, Republic of Korea.
authors.forename: Seok-Jun
authors.initials: SJ
authors.lastname: Seo
authors.forename: Hongrae
authors.initials: H
authors.lastname: Jeon
authors.forename: Jae Kwang
authors.initials: JK
authors.lastname: Lee
authors.forename: Gha-Young
authors.initials: GY
authors.lastname: Kim
authors.forename: Daewook
authors.initials: D
authors.lastname: Park
authors.forename: Hideo
authors.initials: H
authors.lastname: Nojima
authors.forename: Jaeyoung
authors.initials: J
authors.lastname: Lee
authors.forename: Seung-Hyeon
authors.initials: SH
authors.lastname: Moon
mesh_terms: D002244:Carbon / Q000737:chemistry; D002413:Cations, Divalent / Q000302:isolation & purification; D002414:Cations, Monovalent / Q000302:isolation & purification; D002606:Charcoal / Q000737:chemistry; D055664:Electrochemical Techniques / Q000295:instrumentation / Q000379:methods*; D004566:Electrodes; D007477:Ions / Q000302:isolation & purification*; D008855:Microscopy, Electron, Scanning; D016062:Porosity; D013499:Surface Properties; D018508:Water Purification / Q000379:methods*; D014880:Water Softening / Q000379:methods*; D017155:Wettability
chemical_list: D002413:Cations, Divalent; D002414:Cations, Monovalent; D007477:Ions; D002606:Charcoal; D002244:Carbon