In-situ Measurement of Oxidation Ability of Thiobacillus ferrooxidans by QCM
Naoki Washizu, Hiroyuki Masuda, Saburo Matsuoka
It is essential to evaluate the activity of bacteria for the prediction of bacterial corrosion rate. Thiobacillus ferrooxidans is a kind of iron oxidizing bacteria and oxidizes Fe2+ to Fe3+ in acid water. T. ferrooxidans plays an important role in microbiologically influenced corrosion. The object of this work is to evaluate the activity of T. ferrooxidans, that is, the oxidation rate of Fe2+. Fe3+ is an oxidizer and can ionize solid Cu. It is, therefore, possible to calculate the oxidation rate by measuring the mass loss of solid Cu. Quartz Crystal Micro balance method (QCM) was used to measure the mass loss of Cu in this experiment. L-ascorbic acid or elemental Fe was necessary to be dosed into bacterial solution in order to reduce excessive Fe3+. As a result of these procedures, it became possible to fix the oxidation rate of Fe2+ by T. ferrooxidans. The oxidation rates were 0.5×10-7, 1.7×10-7 and 4.1×10-7mol Fe·dm-3·s-1 after 90, 120 and 150h from the inoculation, respectively.