Scalable Approach to Highly Efficient and Rapid Capacitive Deionization with CNT-Thread As Electrodes

Abstract

A scalable route to highly efficient purification of water through capacitive deionization (CDI) is reported using CNT-thread as electrodes. Electro-sorption capacity (q) of 139 mg g and average salt-adsorption rate (ASAR) of 2.78 mg gmin achieved here is the highest among all known electrode materials and nonmembrane techniques, indicating efficient and rapid deionization. Such exceptional performance is achieved with feedstock concentrations (≤1000 ppm) where conventional techniques such as reverse osmosis and electrodialysis prove ineffective. Further, both cations (Na, K, Mg, and Ca) and anions (Cl, SO and NO) are removed with equally high efficiency (∼80%). Synergism between electrical conductivity (∼25 S cm), high specific surface area (∼900 m g), porosity (0.7 nm, 3 nm) and hydrophilicity (contact angle ∼25°) in CNT-thread electrode enable superior contact with water, rapid formation of extensive electrical double layer and consequently efficient deionization. The tunable capacitance of the device (0.4-120 mF) and its high specific capacitance (∼27.2 F g) enable exceptional performance across a wide range of saline concentrations (50-1000 ppm). Facile regeneration of the electrode and reusability of the device is achieved for several cycles. The device demonstrated can desalinate water as it trickles down its surface because of gravity, thereby eliminating the requirement of any water pumping system. Finally, its portable adaptability is demonstrated by operating the device with an AA battery.

Dimensional optimization enables high-performance capacitive deionization

“…82,83 The carbonized puried carbon nanotube electrode shows the highest adsorption ability, with the highest pore specic volume and the largest specic surface area, and the rate of NaCl desorption is close to 90%. 83 Moronshing et al used CNT wire as an electrode to achieve a high-efficiency CDI water purication path (of 139 mg g À1 electrosorption capacity and 2.78 mg g À1 min À1 average salt adsorption rate) 84 (Fig. 4a-h).…”

“…The synergetic effect of the carbon nanotube threaded electrode's physical properties (with the electric conductivity as high as 25 S cm À1 , large specic surface area up to 900 m 2 g À1 , high porosity (0.7 nm, 3 nm) and excellent hydrophilicity with the contact angle of 25 ) increased the good contact between the electrode and water, making the rapid formation of a wide range of electric double layers, thereby being effectively deionized. 84 Electrophoretic deposition (EPD) was introduced by Zhang et al as a new attempt to fabricate carbon nanotube (CNT) electrodes, and a crack-free electrode surface was obtained 85 (Fig. 4i and j).…”

“…Reproduced with permission. 84 Copyright 2017, American Chemical Society. SEM images of the cross-sectional view (i) and top view (j) of the deposited CNT electrode.…”

ELECTROSORPTION OF SALT IONS USING TITANIUM DIOXIDE-DECORATED rGO AS A PROMISING ELECTRODE CANDIDATE

“…Cyclic voltammetry (CV) is used as an efficient method for detecting the performance of electrosorption and examining CDI electrode materials by specific capacitance [35][36][37]. CV tests were performed in a three-electrode scheme to determine the electrochemical efficiency of TiO 2 -deposited rGO as electrodes.…”

Environmental Remediation Applications of Carbon Nanotubes and Graphene Oxide: Adsorption and Catalysis

“…This study revealed that the formation of small organic molecules by ring cleavage reaction and direct mineralization to CO 2 and NO 3 − might be two potential pathways for electrochemical degradation of pyridine. Moronshing et al recently reported a scalable approach to achieve efficient water purification by rapid capacitive deionization (CDI) with CNT-thread as electrodes [81]. Due to the synergism between electrical conductivity (~25 S cm −1 ), high specific surface area (~900 m 2 g −1 ), porosity (0.7 nm, 3 nm) and hydrophilicity (contact angle ~25°) in CNT-thread electrode, the extensive electrical double layer will come to rapid formation after contacting with water, and resulting in consequently efficient deionization.…”