A kinetic approach to study cobalt, copper and arsenic bioleaching has been proposed and discussed. Two flotation by-products from the Lubin mine have been used. Acidithiobacillus ferrooxidans bacteria isolated from water from the “colour” lakes of Boguszow (Lower Silesia), was adopted to metal leaching. Semi-empirical model has been proposed to describe the metal extraction from collected samples. This model originated from the shrinking core and it was able to fit the experimental data. This model is an useful tool to investigate and compare ore bioleaching process for different size fractions.