The accuracy of oxygen flux measurements using microelectrodes

[摘要] An electrochemical analog of a biofilm was constructed to test the accuracy of oxygen flux measurements using microelectrodes. We used a cathodically polarized graphite felt attached to the bottom of a Bat plate open channel reactor as the reactive surface consuming oxygen. The oxygen flux to the felt was calculated from the polarization current. Microelectrodes were used to measure the oxygen profiles above and within the graphite felt. From the shape of the oxygen profile we evaluated the oxygen Aux to the graphite fell. This provided us with two sets of data, the true oxygen flux, calculated from polarization current, and the oxygen flux estimated from microelectrode measurements. Comparing these two fluxes, for different Bow velocities, showed that the fluxes evaluated from the polarization current were different from those evaluated from the oxygen profiles. The differences were likely caused by the presence of the microelectrode in the mass boundary layer and/or by the simplifying assumptions accepted in computational procedures employed to calculate oxygen fluxes. For low flow velocities, between zero and 1.0 cm s(-1), the differences were velocity sensitive; the higher the Bow velocity, the bigger the difference. For higher flow velocities, between 1 cm s(-1) and 3 cm s(-1) the flux of oxygen estimated from the microelectrode measurements was consistently approximately 80% higher than the true oxygen flux estimated from the polarization current. (C) 1998 Elsevier Science Ltd. All rights reserved.

[发布日期] 1998-12-01

[关键词] microelectrodes;biofilms;concentration gradients