| Summary: | 碩士 === 國立交通大學 === 環境工程系所 === 105 === Capacitive deionization (CDI) is an emerging water treatment process with low energy consumption, high recovery rate, easy assemble, and can be operated under normal temperature and pressure, that shows its application on desalination of seawater or industrial wastewater. MnO2, a pseudo-capacitive material is one of the promising electrode material for CDI applications because of its high capacity, low cost and environment friendly.
In this study, nanorod and nanoneedle α-MnO2 were synthesized by hydrothermal method. Afterward, α-MnO2 was assembled with carbon black (CB) to fabricate α-MnO2 nanorod and α-MnO2 nanoneedle composite electrodes. Their desalination performance and ionic selectivity with different ionic valence states and hydrated radius were be investigated.The optimization of CDI operation by adjustment of applied current, cell voltage of test solution was also conducted.The results show that α-MnO2 nanoneedle has relatively larger surface area, porous volume, and higher roughness than α-MnO2 nanorod. In comparison to α-MnO2 nanoneedle, α-MnO2 nanorod exhibits a higher current density, but the specific capacitance of α-MnO2 nanorod and nanoneedle decrease when the solution concentration nears 2000 mg/L. The results also show that, with different cell voltages and current densities, the maximum electrosorption capacity occurres in constant voltage mode. The α-MnO2 nanorod composite electrodes (40 mg/g as KCl) shows higher electrosorptive capacity than α-MnO2 nanoneedle composite electrodes (33.6 mg/g as KCl) in 30 minutes reaction, indicating its applicable for CDI because of its better accessibility and excellent electrochemical properties for ion transportation in aqueous solution. And, the α-MnO2 nanorod composite electrodes precesses higher electrosorptive capacity in potassium chloride solution, because of its the highest mobility and the smallest hydrated radius comparing with other cations.
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