E. Donati

Microbial Processing of Metal Sulfides

Preface Section I - Fundamentals, microorganisms and mechanisms Microorganisms involved in bioleaching and nucleic acid-based molecular methods for their identification and quantification Axel Schippers Mechanisms and biochemical fundamentals of bacterial metal sulfide oxidation Thore Rodwerder and Wolfgang Sand Electrochemical techniques used to study bacterial-metal sulfides interactions Denise Bevilaqua, Heloisa A. Acciari, Assis V. Benedetti and Oswaldo Garcia Jr Electrochemical mechanism of leaching. Influence of the presence of catalytic ions and bacteria Antonio Ballester, Maria Luisa Blazquez, Felisa Gonzalez and Jesus A. Munoz Recovery of zinc, nickel, cobalt and other metals by bioleaching Marisa R. Viera, Cristina M. Pogliani and Edgardo R. Donati Bioleaching of metals in neutral and slightly alkaline environment Aleksandra Sklodowska and Renata Matlakowska Section II - Bioreactors and Bioheaps Bioleaching of sulfide minerals in continuous stirred tanks Dominique Henri Roger Morin Bioreactor design fundamentals and their application to gold mining Fernando Acevedo and Juan Carlos Gentina Air-lift reactors: characterization and applications in biohydrometallurgy Alejandra Giaveno, Laura Lavalle, Patricia Chiacchiarini and Edgardo R. Donati Principles, mechanisms and dynamics of chalcocite heap bioleaching Jochen Petersen and David G. Dixon Section III - Genetics and Molecular Biology The use of bioinformatics and genome biology to advance our understanding of bioleaching microorganisms Raquel Quatrini, Jorge Valdes, Eugenia Jedlicki and David S. Holmes Proteomics and metaproteomics applied to biomining microorganisms Carlos A. Jerez Cell-cell communication in bacteria: A promising new approach to improve bioleaching efficiency? Susana Valenzuela,Alvaro Banderas, Carlos A. Jerez and Nicolas Guiliani Section IV - Other Applications Bioflotation and bioflocculation of relevance to minerals Bioprocessing K. Hanumantha Rao and S. Subramanian Desulphurization of gaseous emissions containing hydrogen sulfide Jose Manuel Gomez and Domingo Cantero Index

Bio-dissolution of spent nickel-cadmium batteries using Thiobacillus ferrooxidans.

In this study, the production of sulphuric acid in bioreactors with Thiobacillus ferrooxidans attached on elemental sulphur was investigated. These bioreactors reached a maximum H+ productivity of 80 mmol kg-1 d-1 of support. This medium was used for the indirect dissolution of spent nickel-cadmium batteries recovering after 93 days 100% of cadmium, 96.5% of nickel and 95.0% of iron. Moreover, recoveries higher than 90.0% were reached when anodic and cathodic materials were directly added to Thiobacillus ferrooxidans cultures with sulphur as the sole energy source. The results presented show an economic and effective method which could be considered the first step to recycle spent and and discarded batteries preventing one of the many problems of environmental pollution.

Immobilisation of Thiobacillus ferrooxidans: importance of jarosite precipitation

Abstract A direct relationship between jarosite precipitation and the number of attached cells were found in Thiobacillus ferrooxidans cultures in the presence of glass beads. Low cell immobilisation was observed on the glass beads; these cells were probably attached to the jarosite deposits on the glass. The presence of glass beads only contributed to biofilm formation increasing jarosite precipitation especially at higher pH values. At a pH value lower than 1.6, a biofilm was not produced due to negligible iron precipitation. Cultures with an initial pH value of 1.8 reached an iron(III) productivity as high as 15 mM h −1 after five successive cultures obtained by transferring previous solid residues to new media.

Factors affecting chromium(VI) reduction by Thiobacillus ferrooxidans

Abstract The ability of Thiobacillus ferrooxidans cultures to reduce chromium(VI) to chromium(III) was evaluated under different conditions. In T. ferrooxidans cultures with sulphur as energy source, the capacity for chromium(VI) reduction was related to the generation of sulphur compounds (sulphite, thiosulphate and polythionates) with high reducing power. In contrast with other chromium(VI)-reducing microorganisms, T. ferrooxidans showed higher chromium(VI) reduction at low pH. The reduction of chromium(VI) also increased with the age of the culture. A T. ferrooxidans cells were capable of growing under anaerobic conditions with chromium(VI) as the terminal-electron acceptor.

A comparison of bioleaching of covellite using pure cultures of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans or a mixed culture of Leptospirillum ferrooxidans and Acidithiobacillus thiooxidans

The aim of this investigation was to determine the efficacy of covellite bioleaching using pure cultures of Acidithiobacillus ferrooxidans or Acidithiobacillus thiooxidans and a mixed culture composed of At. thiooxidans and Leptospirillum ferrooxidans. The experiments were carried out in shake flasks with or without iron(II) (1 g/L as ferrous sulphate) at pH 2.0. Inocula of both iron-oxidising bacteria were obtained from cultures with iron(II) as the sole energy source, whereas At. thiooxidans inoculum was taken from a culture growing on sulphur. The solubilisation of copper in flasks inoculated with At. thiooxidans was greatly enhanced in the presence of additional iron(II) achieving 62% copper extraction in 30 days. This result agrees with a mechanism proposed recently. On the other hand, the effect of supplemental iron was not so important for covellite leaching by the At. ferrooxidans culture and the mixed culture. Copper solubilisation by the At. ferrooxidans culture was nearly the same as that for the mixed culture (51% versus 55%).

Bioleaching of covellite using pure and mixed cultures of Thiobacillus ferrooxidans and Thiobacillus thiooxidans

Abstract A high level of covellite (CuS) dissolution was observed in systems containing Thiobacillus thiooxidans and iron. This activity was higher than with Thiobacillus ferrooxidans in the same medium and lower than that with T. ferrooxidans in the absence of iron. In mixed cultures, covellite dissolution appeared to be associated with T. ferrooxidans in the presence of iron and sulphur but with T. thiooxidans when these were absent.

BACTERIAL ATTACHMENT : ITS ROLE IN BIOLEACHING PROCESSES

Abstract A clear relationship was observed between the adhesion of Thiobacillus ferrooxidans and Thiobacillus thiooxidans to different substrates and the nutrient composition of the culture medium used for growth. However, a linear relationship between the percentage of attachment and the efficiency of bioleaching by these microorganisms was not found. The direct attack mechanism on insoluble sulphides by Thiobacillus ferrooxidans was confirmed in the absence of iron.

Effect of iron (III) and its hydrolysis products (jarosites) onThiobacillus ferrooxidans growth and on bacterial leaching

SummaryThere is a significant inhibition of the growth ofThiobacillus ferrooxidans in the presence of iron (III), but this does not affect bacterial leaching. Moreover, the insoluble hydrolytic products (jarosites) have no influence, except from a mechanical point of view when they are generated ‘in situ’.

Mechanisms involved in bioleaching of an aluminosilicate by heterotrophic microorganisms

Mechanisms involved in bioleaching of an aluminosilicate (95% of spodumene) by heterotrophic microorganisms were investigated. Two moulds (Aspergillus niger and Penicillium purpurogenum) and a yeast (Rhodotorula rubra), all isolated from the mineral, were assayed. The mineral was put into the bioleaching medium under two different conditions: free or into a dialysis tube. The bioleaching mechanism for A. niger or P. purpurogenum was related to the production of low molecular weight metabolites, mainly organic acids. In contrast, bioleaching by R. rubra was related to its metabolic activity and to structural macromolecules of the capsule and the cell wall.

Zinc and cadmium biosorption by untreated and calcium-treated Macrocystis pyrifera in a batch system.

Zinc and cadmium can be efficiently removed from solutions using the brown algae, Macrocystis pyrifera. Treatment with CaCl(2) allowed stabilization of the biosorbent. The maximum biosorption capacities in mono-component systems were 0.91 mmol g(-1) and 0.89 mmol g(-1) and the Langmuir affinity coefficients were 1.76 L mmol(-1) and 1.25 L mmol(-1) for Zn(II) and Cd(II), respectively. In two-component systems, Zn(II) and Cd(II) adsorption capacities were reduced by 50% and 40%, respectively and the biosorbent showed a preference for Cd(II) over Zn(II). HNO(3) (0.1M) and EDTA (0.1M) achieved 90-100% desorption of both ions from the loaded biomass. While HNO(3) preserved the biomass structure, EDTA destroyed it completely. Fourier transform infrared spectra identified the contribution of carboxylic, amine and sulfonate groups on Zn(II) and Cd(II) biosorption. These results showed that biosorption using M. pyrifera-treated biomass could be an affordable and simple process for cadmium and zinc removal from wastewaters.