Juan Carlos Gentina

Bioleaching of minerals — a valid alternative for developing countries

Abstract The feasibility of applying bacterial leaching of minerals in developing countries is analyzed. There are several examples that show the economic viability of this technology. The Chilean experience in this area is presented as a case study. The concerted effort that was made during the last decade, allowed a technology transfer from experimental stage to commercial exploitation of copper ores.

Process engineering aspects of the bioleaching of copper ores

The bioleaching of minerals is a complex process that is affected by a number of biological, mineralogical, electrochemical and engineering factors. This work presents and discusses the most significant process engineering aspects involved in the bacterial leaching of copper ores, i.e. bacterial population, type of mineral and particle size, nutrients and inhibitors, oxygen and carbon dioxide, temperature and pH, leaching kinetics and operation mode.It is concluded that more work is needed in this area in order to gain a deeper insight in the many factors that govern this process. This would allow to significantly improve its overall productivity.

Microbial ore leaching in developing countries

Abstract Microbial leaching processes are being considered as an economical and technically viable alternative for processing low-grade ores and wastes in developing countries. The research and development programs in developing countries aim to design appropriate technologies for the large scale exploitation of local mines. In most cases mining companies, universities, research institutes and governmental and international agencies are all involved, demonstrating a widespread confidence in the application of this technology.

Attachment behaviour of Thiobacillus ferrooxidans cells to refractory gold concentrate particles

In the biooxidation of minerals, cells of Thiobacillus are distributed between the surface of the particles and the liquid. This work quantifies the kinetics of attachment, the equilibrium between attached and suspended cells, and the influence of ferric ion and particle size on this phenomenon. The attachment kinetics were fast, the equilibrium was reached in 10 to 30 minutes, depending on the initial population. The equilibrium curves showed three distinct phases, and the first two could be modelled by Langmuir equations. The maximum concentration of attached cells increases with the addition of ferric ions and decreases with particle size.

Biooxidation of an enargite-pyrite gold concentrate in aerated columns

The performance of 5-L laboratory bubbling columns in the biooxidation of a Chilean gold concentrate by Thiobacillus ferrooxidans was evaluated at pulp densities in the range of 6 to 24 % w/v and aeration rates of 3.0 to 4.5 vvm at pH 2.4 and 33°C. The concentrate contained 42 g gold/t, 41% enargite and 43% pyrite. Cell growth in the liquid and solid phases was observed only during the first days of operation. Growth was accompanied by a sustained solubilisation of Cu, Fe and As, and by a rapid increase in Eh from 400 to 610 mV. After this period, growth on the mineral surface stopped for reasons that are not apparent at this time. From then on, only a slight increase in the suspended population occurred. Nevertheless, the oxidative activity persisted throughout the 24-day period of each rtm. The highest rates of leaching were at 3.0 vvm and 24% solids. The results show a good performance of the columns and confirm the refractory nature of the enargite-pyrite concentrate.

Continuous biooxidation of a refractory gold concentrate

Biooxidation of a refractory gold concentrate in a continuous culture operation utilising a Thiobacillus ferrooxidans strain was studied. The experiments were conducted in a 5 L bioreactor using a 6% (w/v) pulp density in the feed stream, dilution rate of solids between 0.088 and 0.92 d -1 , pH 1.5 and 33°C. Main sulphur compounds of the concentrate were 41% enargite and 43% pyrite. Cell, ferric ion and sulphate productivity present a maximum at a solids dilution rate in the range of 0.6 – 0.8 d -1 . The presence of iron and negligible amounts of arsenic in solution are indicative that cells utilises pyrite as energy source rather than enargite. Specific growth rate and cell yield associated to solids present a saturation type curve as a function of solids dilution rate. The increment of cell growth and mineral dissolution as consequence of step changes, either lowering particle size or air enrichment with CO 2 , reflect a condition of a double limitation of the continuous culture, energy and carbon sources respectively.

A semi-structured model for the growth and β-Galactosidase production by fed-batch fermentation of Kluyveromyces marxianus

Abstract A model is proposed to describe the growth and β-Galactosidase production by Kluyveromyces marxianus. It shows good agreement with the experimental data over a range of conditions. It also reliably predicts the effect of growth rate on the productivity of the protein. The simplicity and accuracy of the model make it suitable for designing and implementing control and optimization strategies for the production of protein at large scale.