Abstract
Metal ion reducing bacteria “Shewanella algae” were used in this experiment to directly reduce copper oxide powder to Cu(0) powder. The liquid medium used for culturing Shewanella algae contained sodium lactate as the electron donor and iron(III) citrate as the electron acceptor.
Results obtained are as follows:
(1)When Cu2O powder was added in the liquid medium, the population of Shewanella algae grew exponentially in two stages. The first exponential growth occurred about 20 hours after the experiment began, and the second growth occurred about 200 hours after the experiment began. No growth of bacteria occurred when CuO powder was added in the liquid medium.
(2)When Cu2O powder was added in the liquid medium, Cu concentration in the liquid medium maintained 0.01 mg/m3 during the first inductive phase and maintained 7 mg/m3 during the second inductive phase. Cu concentration decreased drastically during the second exponential growth phase. When the bacterial culture reached the stationary phase, Cu concentration still decreased slightly and dropped to approximately 0.07 mg/m3 at the end of the experiment.
(3) Three different types of reduced Cu(0) particles were observed: ultra fine particles on the surface of Shewanella algae cells; spherical, triangular and hexagonal particles of sub-micron size obtained from the liquid medium; and many particles which are similar in shape and size to raw Cu2O powder.
