Understanding the role of Fe(III)/Fe(II) couple in mediating reductive transformation of 2-nitrophenol in microbial fuel cells

The Fe(III)/Fe(II) couple can play a significant role in the abiotic reduction of 2-nitrophenol (2-NP) at the cathode chamber of a microbial fuel cell (MFC). Experimental results demonstrate that Fe(II) addition to the cathode chamber contributes to a significant increase in the reaction rate of 2-NP removal and the power performance of MFC. Observed pseudo first-order rate constants and power densities are heavily dependent on the identity of the Fe(II)-complexing ligands. The Fe(II) complex coordinated with citrate results in the highest rate constant up to 0.12 h−1 as compared to other organically complexed iron species including Fe(II)–EDTA, Fe(II)–acetate and Fe(II)–oxalate, and iron species uncomplexed with any organic ligands. In addition, the presence of Fe(II)–citrate species leads to a maximum volumetric power density of 1.0 W m−3, which is the highest value among those obtained with other iron species for the similar MFC system.