1. Efficient groundwater defluorination over a wide concentration gradient through capacitive deionization with a three-layer structured membrane coating electrode.
- Author
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Wang, Chengyi, Qiu, Yangbo, Wang, Chao, Xu, Yubo, Ren, Long-Fei, and Shao, Jiahui
- Subjects
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DEIONIZATION of water , *CONCENTRATION gradient , *GROUNDWATER , *GROUNDWATER pollution , *ELECTRODES , *POLYMERIC membranes - Abstract
Fluoride (F−) pollution in groundwater is an important environmental issue and capacitive deionization (CDI) holds promise for defluorination at moderate concentrations (e.g., 200 −1000 mg L−1). However, existing electrodes suffer from the overlap of electrical-double-layer (EDL) and severe co-ion effects at low (e.g., <200 mg L−1) and high sodium fluoride (NaF) concentrations (e.g., >1000 mg L−1), respectively, exhibiting poor salt adsorption capacity (SAC). Hence, a three-layer structured electrode, "membrane/carbon nanotube (CNT)/activated carbon (AC)" (CNT-MCE), was prepared through electrospinning CNT onto AC, followed by a polymer membrane coating. Compared to AC and membrane coated electrode, CNT-MCE with mesopore-dominated structure prevented EDL overlap, achieving a higher SAC of 40.8 mg g−1 at 100 mg L−1 NaF. At 1500 mg L−1 NaF, the positively charged CNT-MCE exhibited an improved SAC of 58.8 mg g−1 by inhibiting co-ion effects. Meanwhile, CNT-MCE consistently demonstrated superb SACs at 200 − 800 mg L−1 NaF and maintained excellent stability over a wide concentration gradient by inhibiting severe oxidation. Notably, CNT-MCE successfully decreased the F− concentration in simulated groundwater from 3.4 to 1.1 mg L−1. Overall, our work provides an efficient strategy of electrode design to broaden the applicability of CDI for groundwater defluorination over a wide concentration gradient. [Display omitted] • Three-layer structured membrane coating electrode was prepared for F- removal. • High F- adsorption capacities were obtained over the wide concentration gradient. • Mesopore-dominated structure overcame the overlapping of electrical double layer. • Positively charged polymer membrane inhibited the serious co-ion repulsion effect. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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