電容去離子(capacitive deionization, CDI)是一種環境友善且低能耗之新興水處理再生技術，而結合離子交換膜(ion exchange membrane, IEM)組成薄膜電容去離子(membrane capacitive deionization, MCDI)系統被認為能提升整體去除性能，極具發展潛力。實際氨氮廢水之組成成分複雜，有效處理以降低污染物濃度對於後續排放或再利用而言極為重要。本研究探討氨氮及廢水中常見四種陰離子(F⁻, Cl⁻, NO3⁻, SO42⁻)分別進行CDI和MCDI程序後的去除效果及其離子競爭吸附行為。使用單鹽溶液進行CDI 後發現四種銨溶液的去除能力優劣與陰離子的水合比有關；在MCDI中，四種銨溶液的去除能力獲得不同程度的提升，且其去除量大小與對應的陰離子價電荷數有關。使用四種銨鹽混合溶液進行的CDI與MCDI程序中也觀察到了相似的結果，此外無論是單鹽或混合溶液，在CDI充電過程中皆觀察到pH值持續上升，這與電極表面之法拉第反應和陰陽離子不對稱去除所導致的氫離子選擇性吸附的非法拉第過程有關；而MCDI充電過程中溶液的pH值變化較小，可能是薄膜能有效避免前述反應的發生。;Capacitive deionization (CDI) is an emerging water regeneration technology because it is environmental friendly and energy-efficient. Combining ion exchange membranes (IEMs), membrane capacitive deionization (MCDI) is believed to enhance overall removal performance and showed great development potential. An effective treatment to reduce pollutant concentrations is crucial for subsequent discharge or reuse. This study investigated the removal and ion competitive adsorption behavior of ammonia-nitrogen and four common anions (F⁻, Cl⁻, NO3⁻, SO42⁻) in CDI and MCDI. In CDI, the removal ability of four ammonium solutions containing only a single salt was related to the hydration ratio of anions. In MCDI, the removal of the four ammonium solutions was improved to varying degrees. The removal efficiency was associated with the valence of anion. Similar results were observed using mixed solutions of the four ammonium salts in both processes. The pH of both single salt and mixed solutions continuously increased during the CDI charging. This was attributed to the non-Faradaic process of selective hydrogen ion adsorption caused by the asymmetrical removal of anions and cations on the electrode surface and the Faradaic reaction. In contrast, the pH of the solution remained relatively stable during the MCDI charging, indicating the membrane effectively prevented the reactions as mentioned above.
