Estudio de la acumulación microbiana de metales y formación de nanopartículas con aplicación potencial en la industria minera

Abstract

The mining industry is an economic activity of great importance and tradition in Mexico. In the particular case of the metals of transition cobalt and copper, his extraction and separation is a complicated process. Since the sources of cobalt are mixed by other metals as the copper. Some bacteria have developed mechanisms that allow them to survive high concentrations of cobalt and copper, using processes that they include from the diffusion of ions in membrane, the use of proteins of transport and quelation (siderophores production) as well as redox enzymes. Some of these processes can derive in the formation of metallic nanoparticles. In this work were evaluated processes of siderophores production of accumulation and adsorption of cobalt and copper. As well as the capacity of formation of nanoparticles of cobalt and copper. Using two bacterial strains named ZnZac and OC4, isolated of mining residues (tailings). There were obtained the values of minimal inhibitory concentration (CMI) for cobalt and copper, locating both strains as moderately resistant. In the results of the tests of bioaccumulation of the strains ZnZac it was capable of accumulating cobalt and not copper, which suggests a selective accumulation. The strains OC4 produced siderophores of the carboxylates type in solid cultures. To analyze the formation of nanoparticles were used two types of electron microscopy, confocal scanning laser (LSCM) and electronic transmission (TEM). The images of LSCM show the presence of copper and cobalt in samples from biomass, from both strains, subject to periods of incubation in solutions with each metal. However it was not observed the formation of nanoparticles by TEM, in this test was evaluated a metal witness (silver). Both strains were capable of forming nanoparticles of silver. The adsorption kinetics behaved pseudo-second-order. With values of adsorptive capacity (qe) of 83.33mgCu/g and 61.34mgCo/g for OC4 strain and ZnZac strain 119mgCu/g y 81.96mgCo/g. Values higher than those reported with other bioadsorbentes. Freudlich model was presented a better fit with the values of adsorption OC4 strain obtained maximum adsorption capacity (qmax) of 155.9 mg/g for copper and 129. 54mg/g for cobalt, Freudlich constant values (k) higher for copper than for cobalt 2.74 and 0.46 respectively, this values that match the affinity. The ZnZac strain reached a maximum adsorption capacity (qmax) calculated, most cobalt than copper 537.55 mg/g and 174.29 mg/g. The ZnZac strain was identified comparing the sequence of 16S, 99% homology with Delftia tsuruhantensis.