Abstract
Natural fluoride-containing waters are characterized by high contents of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC). For the first time, the impact of DIC and DOC on fluoride removal by membrane capacitive deionization (MCDI) was unravelled. A series of MCDI experiments were conducted by mixing NaF solutions with three DIC species (H2CO3, NaHCO3, and Na2CO3) and a DOC representative (humic acid). All three DIC species decrease fluoride removal, among which CO32− causes the greatest reduction. This is because the divalent CO32− is preferably adsorbed by MCDI over monovalent DIC ions. When the initial concentrations of F− and DIC ions are equal, F− is less adsorbed than DIC because the stronger hydration energy of F− makes its interaction with the electrode more difficult. DIC species also act as a buffering agent, reducing pH fluctuations during the adsorption and desorption cycle. On the other hand, DOC at a moderate concentration (10.9 mg/L) has an insignificant impact on fluoride removal. DIC significantly decreases both fluoride and DOC removal in ternary fluoride-rich water. This work highlights the importance of water characteristics in the selective removal of ions and demonstrates the potential applicability of MCDI to treat natural waters.
Original language | English |
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Article number | 115618 |
Journal | Desalination |
Volume | 528 |
Early online date | 11 Feb 2022 |
DOIs | |
Publication status | Published - 15 Apr 2022 |
Acknowledgements
The authors acknowledge the valuable information provided by Joshua Summers (Voltea) and helpful comments from the anonymous reviewers.Keywords
- Dissolved inorganic carbon
- Dissolved organic carbon
- Fluoride
- Humic acid
- Membrane capacitive deionization
- Water treatment
ASJC Scopus subject areas
- General Chemistry
- General Chemical Engineering
- General Materials Science
- Water Science and Technology
- Mechanical Engineering