Estudio de procesos para la solubilización y precipitación de iones metálicos contaminantes mediante bacterias azufre-oxidantes y sulfatoreductoras

Abstract

In recent years, the heavy metal contamination in the environment, due to the high industrial and mining activities, have produced the development of several technologies with the aim of reducing or removing heavy metals from contaminated media in a simple and economical way, among them the bioprocess are relevant.Techniques as bioleaching, biosorption and bioprecipitation apply the microorganism capacities to modify the solubility of heavy metals.Bioleaching consists of the solubilization of heavy metal ions from insoluble compounds. Among the microorganisms that have this capacity, acidophilic bacteria are the most important, in particular, the genus Acidithiobacillus . Besides, these bacteria can reduce Cr(VI) to Cr(III) a more stable and less toxic heavy metal ion.The bioprecipitation allows the transformation of soluble metallic compounds in other insoluble and more stable compounds. Sulphate-reducing bacteria, the genus Desulfovibrio, are able to carry out this kind of processes.The integration of both processes allows the solubilization of heavy metal from insoluble compounds of contaminated media and then can be precipitated as insoluble compounds again which can be deposited or reused out of the original position.The present work concerns: (1) the study of solubilization processes of insoluble compounds of Cr(III), Ni(II) and Zn(II), in discontinue and continue operation mode, by sulphur-oxidizing bacteria Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans. (2) the study of reduction of Cr(VI) to Cr(III) by sulphur-oxidizing bacteria in discontinue and continue operation mode. (3) the study of precipitation of Cr(III), Ni(II) and Zn(II) with sulphate-reducing bacteria, Desulfovibrio vulgaris and Desulfovibrio sp., in discontinue and continue systems. (4) the integration of studied process in an unique system in continue operation mode.