title: Individual and competitive removal of heavy metals using capacitive deionization.
abstract: This study presents the viability and preference of capacitive deionization (CDI) for removing different heavy metal ions in various conditions. The removal performance and mechanisms of three ions, cadmium (Cd(2+)), lead (Pb(2+)) and chromium (Cr(3+)) were investigated individually and as a mixture under different applied voltages and ion concentrations. It was found that CDI could effectively remove these metals, and the performance was positively correlated with the applied voltage. When 1.2 V was applied into solution containing 0.5mM individual ions, the Cd(2+), Pb(2+), and Cr(3+) removal was 32%, 43%, and 52%, respectively, and the electrosorption played a bigger role in Cd(2+) removal than for the other two ions. Interestingly, while the removal of Pb(2+) and Cr(3+) remained at a similar level of 46% in the mixture of three ions, the Cd(2+) removal significantly decreased to 14%. Similar patterns were observed when 0.05 mM was used to simulate natural contaminated water condition, but the removal efficiencies were much higher, with the removal of Pb(2+), Cr(3+), and Cd(2+) increased to 81%, 78%, and 42%, respectively. The low valence charge and lack of physical sorption of Cd(2+) were believed to be the reason for the removal behavior, and advanced microscopic analysis showed clear deposits of metal ions on the cathode surface after operation.
authors.affiliation: Department of Civil, Environmental, and Architectural Engineering, University of Colorado Boulder, Boulder, CO 80309, USA.
authors.forename: Zhe
authors.initials: Z
authors.lastname: Huang
authors.affiliation: Department of Civil, Environmental, and Architectural Engineering, University of Colorado Boulder, Boulder, CO 80309, USA.
authors.forename: Lu
authors.initials: L
authors.lastname: Lu
authors.affiliation: Access Business Group LLC, 7575 Fulton Street East, Ada, MI 49301, USA.
authors.forename: Zhenxiao
authors.initials: Z
authors.lastname: Cai
authors.affiliation: Department of Civil, Environmental, and Architectural Engineering, University of Colorado Boulder, Boulder, CO 80309, USA. Electronic address: jason.ren@colorado.edu.
authors.forename: Zhiyong Jason
authors.initials: ZJ
authors.lastname: Ren
keywords: Capacitive deionization; Electrosorption; Heavy metal; Physical sorption