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Title: Using Ultramicroporous Carbon for the Selective Removal of Nitrate with Capacitive Deionization

Journal Article · · Environmental Science and Technology

The contamination of water resources with nitrate is a growing and significant problem. Here we report the use of ultramicroporous carbon as a capacitive deionization (CDI) electrode for selectively removing nitrate from an anion mixture. Through moderate activation, we achieve a micropore-size distribution consisting almost exclusively of narrow (<1 nm) pores that are well suited for adsorbing the planar, weakly hydrated nitrate molecule. Cyclic voltammetry measurements reveal an enhanced capacitance for nitrate when compared to chloride as well as significant ion sieving effects when sulfate is the only anion present. We measure high selectivities (S) of both nitrate over sulfate (SNO3/SO4 = 17.8 ± 3.6 at 0.6 V) and nitrate over chloride (SNO3/Cl = 6.1 ± 0.4 at 0.6 V) when performing a constant voltage CDI separation on 3.33 mM/3.33 mM/1.67 mM Cl/NO3/SO4 feedwater. Furthermore, these results are particularly encouraging considering that a divalent interferant was present in the feed. Using molecular dynamics simulations, we examine the solvation characteristics of these ions to better understand why nitrate is preferentially electrosorbed over sulfate and chloride.

Research Organization:
Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
Sponsoring Organization:
USDOE National Nuclear Security Administration (NNSA)
Grant/Contract Number:
AC52-07NA27344
OSTI ID:
1572601
Report Number(s):
LLNL-JRNL-768579; 959495
Journal Information:
Environmental Science and Technology, Vol. 53, Issue 18; ISSN 0013-936X
Publisher:
American Chemical Society (ACS)Copyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 80 works
Citation information provided by
Web of Science

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Cited By (4)

Specific ion effects at graphitic interfaces journal October 2019
Selective ion separation by capacitive deionization (CDI) based technologies: a state-of-the-art review journal January 2020
Emerging investigator series: capacitive deionization for selective removal of nitrate and perchlorate: impacts of ion selectivity and operating constraints on treatment costs journal January 2020
Similarities and differences between potassium and ammonium ions in liquid water: a first-principles study journal January 2020