Current recovery from sewage wastewater using electrochemically oxidized graphite felt

Area of Science:

• Electrochemistry
• Environmental Science
• Biotechnology

Background:

• Microbial fuel cells (MFCs) offer a promising route for simultaneous wastewater treatment and energy recovery.
• Carbon anode performance is critical for optimizing electricity generation in MFCs.
• Electrochemical oxidation is explored as a method to enhance anode properties.

Purpose of the Study:

• To investigate the efficacy of electrochemically oxidized graphite felt (EOGF) as an anode material in MFCs for sewage wastewater treatment.
• To evaluate the impact of electrochemical oxidation on anode characteristics and electricity recovery.
• To assess the overall energy balance and performance of MFCs utilizing EOGF anodes.

Main Methods:

• Graphite felt (GF) was electrochemically oxidized using 2 V polarization in sulfuric or nitric acid to produce EOGF.
• EOGF anodes were tested in MFCs with sewage sludge, operating at 0.2 V vs. Ag/AgCl.
• Performance metrics including maximum current, current density, chemical oxygen demand (COD) removal, and net energy balance were measured.

Main Results:

• Nitric acid-treated EOGF demonstrated a higher maximum current (110 μA cm⁻³) compared to untreated GF (91 μA cm⁻³) during electrochemical cultivation.
• Electrochemical oxidation reduced charge-transfer resistance and increased anode capacitance.
• MFCs with EOGF anodes achieved electricity generation of 340-560 mW m⁻³-MFC, with current densities of 11-15 μA cm⁻³.
• COD removal rates and microbial community structure remained unaffected by anode electrochemical oxidation.
• MFCs operated for over three days achieved a positive net energy balance when coupled with post-aeration.

Conclusions:

• Electrochemical oxidation, particularly with nitric acid, enhances the electrochemical properties of graphite felt anodes for MFC applications.
• While EOGF improves anode performance, other factors limit overall current production in the MFC system.
• MFCs with EOGF anodes show potential for net energy recovery from sewage wastewater, especially when integrated with post-treatment processes.