Oxidative dissolution of chalcopyrite by Acidithiobacillus ferrooxidans analyzed by electrochemical impedance spectroscopy and atomic force microscopy.

The microbiological leaching of chalcopyrite (CuFeS(2)) is of great interest because of its potential application to many CuFeS(2)-rich ore materials. However, the efficiency of the microbiological process is very limited because this mineral is one of the most refractory to bacterial attack. Knowledge of bacterial role during chalcopyrite oxidation is very important in order to improve the efficiency of bioleaching operation. The oxidative dissolution of a massive chalcopyrite electrode by Acidithiobacillus ferrooxidans was evaluated by electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM). A massive chalcopyrite electrode was utilized in a Tait-type electrochemical cell in acid medium for different immersion times in the presence or absence of bacterium. The differences observed in the impedance diagrams were correlated with the adhesion process of bacteria on the mineral surface.

Concentrations of mercury, copper, cadmium and lead in fruiting bodies of edible mushrooms in the vicinity of a mercury smelter and a copper smelter.

Four elements were determined in wild growing mushrooms collected in the vicinity of two metal smelters up to a distance of 6 km between 1990 and 1993. The smelters in eastern Slovakia are 15 km apart. Elements were determined by atomic absorption spectrometry in 113 samples of 34 species. The values observed in mushrooms from different parts of Bohemia were used as the background levels. Concentrations of mercury were extremely high in mushrooms grown in the mercury smelter area, especially those in Lepiota procera with mean and maximal values of 119 and 200 mg kg-1 dry matter, respectively. Considerably elevated mercury concentrations were also found in the copper smelter area, especially in Lepista nuda with a mean value 84.7 mg kg-1 dry matter. In both species there were also increased copper concentrations exceeding 200 mg kg-1 dry matter and in the copper smelter area there were high lead values in Lepiota procera and Lepista nuda at 26.4 and 15.3 mg kg-1 dry matter, respectively. Mean cadmium concentrations were also increased in the copper smelter area, but with values < 7 mg kg-1 dry matter. Thus, the mushrooms from both areas should not be consumed at all.