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Study of the Adhesion Mechanism of Acidithiobacillus ferrooxidans to Pyrite in Fresh and Saline Water

Department of Metallurgical Engineering and Materials, Universidad Técnica Federico Santa María, Valparaíso 2340000, Chile
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Minerals 2019, 9(5), 306; https://doi.org/10.3390/min9050306
Received: 11 March 2019 / Revised: 5 May 2019 / Accepted: 10 May 2019 / Published: 17 May 2019
(This article belongs to the Special Issue Microorganisms–Minerals Interactions in Aquatic Environments)
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Abstract

In the present work, the streaming potential of A. ferrooxidans and pyrite was measured in two environments: fresh and saline water (water with 35 g/L of NaCl) at different pH values. Also, attachment kinetics of A. ferrooxidans to pyrite was studied in fresh and saline water at pH 4. The results show that A. ferrooxidans and pyrite had lower streaming potentials (comparing absolute values) in saline water than in fresh water, indicating the compression in the electrical double layer caused by Cl- and Na+ ions. It was also determined that the bacteria had a higher level of attachment to pyrite in fresh water than in saline water. The high ionic strength of saline water reduced the attractive force between A. ferrooxidans and pyrite, which in turn reduced bacterial attachment. Electrostatic interactions were determined to be mainly repulsive, since the bacteria and mineral had the same charge at pH 4. Despite this, the bacteria adhered to pyrite, indicating that hydrophobic attraction forces and Lifshitz–van der Waals interactions were stronger than electrostatic interactions, which caused the adhesion of A. ferrooxidans to pyrite.
Keywords: streaming potential; Acidithiobacillus ferrooxidans; pyrite streaming potential; Acidithiobacillus ferrooxidans; pyrite
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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San Martín, F.; Aguilar, C. Study of the Adhesion Mechanism of Acidithiobacillus ferrooxidans to Pyrite in Fresh and Saline Water. Minerals 2019, 9, 306.

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