Desalination mechanism of modified activated carbon/carbon nanotubes composite electrode

Abstract Modified activated carbon/carbon nanotubes (AC*/CNT*) composite electrode was used as the electrode in a capacitive deionization (CDI) process for desalination in this study. The morphology and electrochemical characteristics of the modified electrode were discussed, and the results showed that after modification, the specific surface area of AC* reached 672.48 m2/g, increased by 29.43%; while the specific surface area of CNT* was 117.39 m2/g, reduced by 9.94% due to the strong oxidation of the mixed acid, the pore volume of CNT* increased by 48.28%. The electrode regeneration test proved that the electrode had good cycling stability. The pseudo-first-order kinetic model could better describe the adsorption rate of the electrodes for ions and the desalination ratio of the AC*/CNT* electrode reached 7.11 mg/g; the Langmuir model could well describe the adsorption mechanism of capacitive deionization, and indicated that the adsorption process of CDI was near to single ion layer adsorption; the change trend of electric mobility with migration time could be well fitted by exponential equations. This study explored a novel composite electrode coating, and initially explored the behavioral characteristics and trends of CDI technology.