Many researchers focus on the microbial fuel cells (MFCs) treating wastewater, due to their distinguished advantages of water purification as well as recovering energy or valuable chemicals. In microbial fuel cells, metal ions play an important role in the conductivity of solution, reactor resistance, power density, electricity production and activity of microorganism. Additionally, the metal ions are also involved into the anode or cathode reaction processes directly or indirectly in the MFCs. The mechanism of MFCs process participated with several metal ions and their influence factors are reviewed in this paper. Moreover, we discuss the advantages and development prospects of the MFCs removing heavy metal ions in wastewater or solid waste.

Contents
1 Introduction
2 Effect of inert metal salts on electrolyte conductivity and on internal resistance for MFCs
3 Effect of metal ions on anodic behavior
3.1 Effect of Ca²⁺ on anodic behavior
3.2 Effect of Fe³⁺ on anodic behavior
3.3 Effect of V⁵⁺ on anodic behavior
3.4 Effect of Mn⁴⁺/Mn²⁺ on anodic behavior
3.5 Effect of Pd²⁺,Au³⁺ on anodic behavior
3.6 Modified anode by other metal ions
3.7 Detection of heavy metal toxicity
4 Effect of metal ions on cathode behavior
4.1 Cu²⁺ used as cathode electron acceptor
4.2 Cr⁶⁺ used as cathode electron acceptor
4.3 Ag⁺ used as cathode electron acceptor
4.4 Effect of Fe³⁺/Fe²⁺ on cathodic behavior
4.5 Other metal ions used as cathode electron acceptor
4.6 Various metal ions used as cathode electron acceptor
4.7 Effects of modified cathode by transition metal ions on the cathode behavior
5 Perspectives