Capacitive deionization of high N-doping carbon nanocages prepared by chemical vapor deposition
Capacitive deionization(CDI)is a novel desalination technology that rapidly removes charged ions from water driven by electric field force.It has great potential in brine pre-concentration and reducing the energy consumption of zero liquid discharge desalination.However,the current CDI technology is limited by the low electro-adsorption active sites and uncontrollable pore structure distribution of porous carbon electrodes,resulting in low desalination capacity and charge efficiency,which hinders its further application.Therefore,highly active surfaces and structurally controllable N-doped carbon nanocages(N-CNC)were constructed by a chemical vapor deposi-tion method using pyridine as a carbon source and alkaline magnesium carbonate as a templating agent to investigate their desalination properties.Through precise control of the carrier gas and pyridine quantities,the resulting N-CNC consists of 3-5 layers of graphi-tized carbon arranged in a hollow rectangular morphology.The average thickness of the outer wall ranges from 1 to 2 nm,with an impres-sive N content reaching up to 4.2%.Benefitting from its exceptional porous structure distribution and rich surface chemistry,N-CNC ex-hibits electrochemical behavior primarily contributed by its pseudo-capacitive properties.The desalination test results of the assembled N-CNC//N-CNC symmetric module using the single-pass desalination mode show that the salt adsorption capacity and charge efficiency are 21.8 mg/g and 82%,respectively,with low energy consumption of 0.71 Wh/g.Further treatment of coal chemical high-salinity water test show excellent anion absorption performance.Electric adsorption desalination capacity of Cl-,SO2-4,NO-3 are 33.4,20.5,8.9 mg/g,of which the selectivity ratio of Cl-/SO2-4 is as high as 5.1.This study provides a simple and controllable preparation method for N-doped carbon nanocage structure,which provides certain theoretical and technical support for the industrialization application of CDI concentrated industrial brine.
pyridinechemical vapor depositioncarbon nano-cagescapacitive desalinationadsorption capacitycoal chemical wastewater
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