Unveiling the mechanism of comparative cathodic reactions on salt removal and electrochemical behavior in microbial desalination cell for high-strength wastewater

• Published in: Results in engineering Vol. 27; p. 106145
• Main Authors: Liu, Chongtao, Ju, Ran, Liu, Zhuangzhuang, Li, Yangyang, Wang, Ling, Jiang, Xiaomei, Zeng, Bing, Wu, Houkai, Tao, Xiuping
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2025; Elsevier
• Subjects: Bioelectricity; Cathodic reaction; Desalination; Microbial desalination cell; Wastewater treatment; CE; Rct; TDS; OCV; FeMDC; PTFE; Bioelectricity; AcMDC; Cathodic reaction; MFC; Wastewater treatment; MDC; DR; EIS; LSV; ORR; BES; CV; Desalination; Rin; COD; SEM; Microbial desalination cell
• ISSN: 2590-1230; 2590-1230
• DOI: 10.1016/j.rineng.2025.106145

•The comparative cathodic reaction by Fe and O2 was used to enhance MDC performance.•The highest pollutant removal and desalination efficiency were both over 90%.•MDC with chemical catalyst obtained higher bioelectricity density (2.45 W/m2).•The FeMDC was beneficial for electron transfer and electrochemical activity.•The migration order for anion was better than cation. Cathodic reactions govern bioenergy recovery and sustainable desalination in microbial desalination cells (MDCs), yet direct comparative assessment of dominant catholytes (oxygen vs. ferricyanide) under identical operational conditions remains absent. In this study, a controlled side-by-side evaluation using parallel MDCs with oxygen or ferricyanide catholytes under equivalent operational settings was developed. The findings indicated that the ferricyanide-based MDC outperformed the air-cathode, with higher power density (2.45 W/m2), desalination efficiency (over 90%), and remarkable removal rate of chemical oxygen demand (94%) and ammonia nitrogen (99%) for high-load wastewater (2000 mg/L chemical oxygen demand). Electrode potential slope analysis showed higher power was due to larger experimental working potential (314 mV) of ferricyanide versus air-cathode (173 mV). Electrochemical behaviors revealed that ferricyanide not only reduced the charge transfer resistance for MDC, but also augmented the cathodic potential and electron transfer efficiency, possessing favorable cathodic reduction kinetics. Furthermore, anions migrated with greater priority than cations, which was attributed to the interplay of electric field and hydrated ionic radius. These findings elucidate kinetic-thermodynamic trade-offs in catholyte selection, providing actionable principles for scalable, energy-efficient MDC design.