Title: Seawater desalination by over-potential membrane capacitive deionization: Opportunities and hurdles

Abstract

The salt removal capacity (SRC) of the carbon electrodes in membrane capacitive deionization (MCDI) is limited by the applied potential (<1.6 V). Thus, enhancement of the SRC is essential before applying MCDI to seawater desalination. This study aims at developing a novel MCDI system for seawater desalination by applying over-potential (OP) to enhance ion-adsorption capacity and kinetics, and by reversing the polarity (RP) of electrodes to improve ion-desorption kinetics (hereafter named OP-MCDI-RP) for seawater desalination. At 2.4 V, the OP-MCDI system with mesoporous carbon demonstrated a SRC value of 64.7 mg g^–1 when desalting 0.5 M NaCl solution, while the OP-CDI system could only remove 8.2 mg g^–1 under identical conditions. Similarly, an OP-MCDI cell using carbon aerogel demonstrated a greater SRC value of 43.4 mg g^–1 in comparison with 12.5 mg g^–1 achieved in OP-CDI. These results indicate that the OP-MCDI system can directly desalt high salinity water regardless of the electrode material. In contrast to the OP-MCDI system, the OP-MCDI-RP system yields a higher regeneration efficiency by applying a reversed low-voltage. It is shown that, under appropriate operating conditions, the OP-MCDI-RP system reduced the electrical conductivity of a seawater sample of 37 practical salinity units by 99.9%, suggestingmore » that the OP-MCDI-RP system can be employed for seawater desalination. In conclusion, due to the dramatic increase in energy demand and insufficient long-term stability caused by high potential and high salt concentration, however, the OP-MCDI-RP process should be further investigated for potential practical applications.« less

Authors:

Tang, Kexin  ^[1];

• Search DOE PAGES for author "Tang, Kexin"
• Search DOE PAGES for ORCID "0000-0001-9147-7995"

Kim, Yong-ha ^[2]; Chang, Junjun ^[3]; Mayes, Richard T.  ^[4];

• Search DOE PAGES for author "Mayes, Richard T."
• Search DOE PAGES for ORCID "0000-0002-7457-3261"

Gabitto, Jorge ^[5]; Yiacoumi, Sotira Z. ^[6]; Tsouris, Costas  ^[7]

• Search DOE PAGES for author "Tsouris, Costas"
• Search DOE PAGES for ORCID "0000-0002-0522-1027"

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+ Show Author Affiliations

1. Georgia Inst. of Technology, Atlanta, GA (United States); Tianjin Univ., Tianjin (People's Republic of China); Chinese Academy of Sciences (CAS), Beijing (China)
2. Georgia Inst. of Technology, Atlanta, GA (United States); Louisiana State Univ., Baton Rouge, LA (United States)
3. Chinese Academy of Sciences (CAS), Beijing (China)
4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
5. Prairie View A&M Univ., Prairie View, TX (United States)
6. Georgia Inst. of Technology, Atlanta, GA (United States)
7. Georgia Inst. of Technology, Atlanta, GA (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Publication Date:

Mon Sep 17 00:00:00 EDT 2018

Research Org.:

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1488696

Grant/Contract Number:  

AC05-00OR22725

Resource Type:

Accepted Manuscript

Journal Name:

Chemical Engineering Journal

Additional Journal Information:

Journal Volume: 357; Journal Issue: C; Journal ID: ISSN 1385-8947

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; Membrane capacitive deionization; Over-potential; Seawater desalination; Mesoporous carbon; Carbon aerogel