| Bioleaching is an interdisciplinary of microbiology and hydrometallurgy. Recently, more attention was paid to bioleaching, especially to bioleaching of valuble metals from low grade ores, as bioleaching has economical, environmental and technical advantages over traditional technology. Leptospirillum ferrooxidans is one of the main bacterium used in microbial leaching. L. ferrooxidans is obligate autotrophy iron oxidizing bacterium, spirilla-shaped, motile, flagellate, Gram-negative. L. ferrooxidans grows best in pH 2.0 and at 37℃. It can grow well in pH 1.0 and has an up-limit growth temperature around 45 °C. L. ferrooxidans plays an important role in bioleaching because it bears low pH and high oxidation-reduction potential (ORP) and high temperature. In the course of pyrite-bioleaching, the rate of metal-dissolving is partially correlated with the amount of biomass. It is important to study the effects of irons and the process operating parameters on the dynamics of cell growth and on ore oxidation.Recent work on bioleaching of pyrite has provided strong evidence that it occurs via a two-step mechanism. According to the direct mechanism, the bacteria possess a specific biological mechanism to degrade the mineral and thereby gain energy directly from the sulfide mineral. On the other hand, according to the indirect mechanism, the ferric ions in solution dissolves the mineral, and the bacteria gain their energy from regenerating the ferric ions. The adsorption of bacteria is a necessary condition for direct contact mechanism. Rojas-Chapana considered that direct and indirect bioleaching worked cooperatively, which was benefit for the growth of bacteria.In this study, the kinetics of the growth of L. ferrooxidans and the dynamic changes of the irons were studied and moddled in liquid mudium. The inhibition effects of ferrous-and ferric-irons on cell growth and oxidation rate of ferrous-iron were studied and moddled. The effects of pH on cell growth and oxidation rate were also studied and modled.Genetic algorithm and tabu search were used in optimization of the model parameters based on the experimental data. The model developed can predict the cell growth and ferrous-iron oxidation very well.The oxidizing ability of L. ferrooxidans on the bioleaching of pyrite was studied and moddled. The dynamics of cell adsorption to the pyrite and the chemical oxidation of ferric-iron were investigated. The mathematical model describing the above dynamic process was established and the model parameters were optimized.Based on the above models, a generalized model of L. ferrooxidans bioleaching wasmade. The simulation results showed that it predicted the bioleaching process well, and was useful for practical application.On-line monitoring and control system was developed and the optimal control of fed-batch culture of L. ferrooxidans in bioleach reactor was made. The biomass of bacteria increased six times high in 9K liquid media under on-line optimal control. The communication modules of 1-7000 series were used for the communications between control computer and the sensors and controllers.Immobilization of L. ferrooxidans on fibre materials were studied and used in converting ferrous-iron into ferric-iron in bioreactor in continuous operating mode. This process was also monitored and controlled automatically by computer.Genetic algorithm and tabu search were studied and used in the optimization of the model parameters. The Runge-Kutta method was used in calculation of the mathematical model. The results show that the model predictions fitted with the experimental data reasonably well.The source code of genetic algorithm, mathematical model, process simulation, online data record and presentation, and on-line monitoring and feedback control were developed using the software Visual Basic (Microsoft Co., USA).
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