Effect of exopolymers on oxidative dissolution of natural rhodochrosite by Pseudomonas putida strain MnB1: An electrochemical study

• The biogeochemical behavior of natural rhodochrosite was investigated by electrochemical methods.
• Bacterial exopolymers contributed to the increasing dissolution of natural rhodochrosite.
• Oxidative dissolution of natural rhodochrosite was well explained by Tafel and EIS analysis.

Oxidative dissolution of natural rhodochrosite by the Mn(II) oxidizing bacterium Pseudomonas putida strain MnB1 was investigated based on batch and electrochemical experiments using natural rhodochrosite as the working electrode. Tafel curves and batch experiments revealed that bacterial exopolymers (EPS) significantly increased dissolution of natural rhodochrosite. The corrosion current significantly increased with reaction time for EPS treatment. However, the corrosion process was blocked in the presence of cells plus extra EPS due to formation of the passivation layer. Moreover, the scanning electron microscopy and the energy dispersive spectroscopy (SEM–EDS) results showed that the surface of the natural rhodochrosite was notably changed in the presence of EPS alone or/and bacterial cells. This study is helpful for understanding the role of EPS in bacterially oxidation of Mn(II). It also indicates that the Mn(II) oxidizing bacteria may exert their effects on Mn(II) cycle and other biological and biogeochemical processes much beyond their local ambient environment because of the catalytically dissolution of solid Mn(II) by EPS and the possible long distance transport of the detached EPS.