Cadmium recovery by coupling double microbial fuel cells

Area of Science:

• Electrochemistry
• Environmental Science
• Biotechnology

Background:

• Microbial fuel cells (MFCs) show promise for energy recovery and pollutant remediation.
• Cadmium recovery from wastewater using MFCs is limited by insufficient power output.
• Hexavalent chromium (Cr(VI)) can be utilized in MFCs for electrochemical applications.

Purpose of the Study:

• To investigate the potential of a double microbial fuel cell (d-MFC) arrangement for enhanced cadmium recovery.
• To evaluate the synergistic effects of Cr(VI) and Cd(II) in a d-MFC system.
• To optimize power generation and energy recovery in MFC technology.

Main Methods:

• A double microbial fuel cell (d-MFC) was constructed, integrating a Cr(VI)-MFC with a Cd(II)-MFC operating as a redox-flow battery.
• The cathode of the Cr(VI)-MFC was optimized using a sulfate buffer.
• Electrical energy generation was assessed with and without an additional passage in the d-MFC.

Main Results:

• The Cr(VI)-MFC significantly complemented the insufficient voltage and power of the Cd(II)-MFC for cadmium recovery.
• Optimized Cr(VI)-MFC achieved a maximum utilization power density of 22.5 Wm(-2), 11.3 times higher than the Cd(II)-MFC alone.
• The d-MFC with an additional passage generated 3 times higher power and 4.2 times higher current density compared to operation without it.
• The observed power boosting was explained by Le Chatelier's principle, accelerating electron generation through rapid electron removal.

Conclusions:

• The d-MFC configuration effectively enhances power output for metal recovery applications.
• Cr(VI) utilization in MFCs offers a viable strategy to overcome power limitations in electrochemical remediation.
• This approach presents a promising method for simultaneous energy recovery and pollutant removal in wastewater treatment.