Mechanism of microbial flotation using Thiobacillus ferrooxidans for pyrite suppression

Abstract

Microbial desulfurization might be developed as a new process for the removal of pyritic sulfur from coal slurries such as coal-water mixture (CWM). An application of iron-oxidizing bacterium Thiobacillus ferrooxidans to flotation would shorten the periods of the microbial removal of pyrite from some weeks by leaching methods to a few minutes. The floatability of pyrite in flotation was mainly reduced by T. ferrooxidans itself rather than by other microbial substances in bacterial culture as additive of flotation liquor. Floatability was suppressed within a few seconds by bacterial contact. The suppression was proportional to increasing the number of cells adhering to the pyrite surface. A linear relationship was observed between bacterial adhesion and the suppression of floatability. If 25% of the total pyrite surface area were covered with the bacteria, pyrite floatability would be completely depressed. Bacteria that lost their iron-oxidizing activities by sodium cyanide treatment were also able to adhere to pyrite and reduced pyrite floatability as much as normal bacteria did. Thiobacillus ferrooxidans ATCC 23270, T-1, 9, and 11, which had different iron-oxidizing abilities, suppressed floatability to similar-levels. The oxidizing ability of bacteria did not influence the suppressing effect. These results showed the mechanism of the suppression of pyrite floatability by bacteria. Quick bacterial adhesion to pyrite induced floatability suppression by changing the surface property from hydrophobic to hydrophilic. The quick adhesion of the bacterium was the novel function which worked to change the surface property of pyrite to remove it from Coal. 0 1993 John Wiley & Sons, Inc.

Selective Adhesion of Thiobacillus ferrooxidans to Pyrite

“…Bacterial adhesion also contributes to microbial flotation for coal desulfurization. Bacterial adhesion changes the surface properties of pyrite in crushed fine coal from hydrophobic to hydrophilic (19). This surface change makes it possible to remove pyrite from coal in flotation systems (2,9).…”

Selective Attachment of Leptospirillum ferrooxidans for Separation of Chalcopyrite and Pyrite through Bio-Flotation

“…The growth and activity of the L.f culture is limited by the availability of ferrous iron for the cell [32]. The change in availability of the ferrous iron between the cultures grown on mineral has a significant decrease in total cell concentration for chalcopyrite growth.…”

Attachment of Acidithiobacillus ferrooxidans to pyrite in fresh and saline water and its fitting to Langmuir and Freundlich isotherms

“…Due to its ability to oxidize ferrous and reduced sulfur compunds, A. ferrooxidans has been widely used in leaching when processing 5 copper oxides and copper sulfides (Donati et al, 2007;Rawlings, 2005). Moreover, A. ferrooxidans has been studied as pyrite depressant in the flotation process (Chandraprabha et al, 2004(Chandraprabha et al, , 2005Hosseini et al, 2005;Mehrabani et al, 2011;Misra et al, 1996;Nagaoka et al, 1999;Ohmura et al, 1993;San Martín et al, 2018). In general, bacteria tend to adhere to solid surfaces forming biofilms rather than remain free in solution as planktonic cells because they find protection against hostile environments and a high concentration of nutrient (Flemming and Wingender, 2010;Schaechter, 2009;Chandraprabha and Natarajan, 2006).…”

“…Microorganisms, including bacterium Acidithiobacillus ferrooxidans, have been used in the flotation and leaching processes (Chandraprabha et al, 2004(Chandraprabha et al, , 2005Hosseini et al, 2005;Mehrabani et al, 2011;Misra et al, 1996;Nagaoka et al, 1999;Ohmura et al, 1993;San Martín et al, 2018;Donati et al, 2007;Rawlings, 2005). In both processes, the adherence of microorganisms 20 to minerals is an important step.…”

“…In both processes, the adherence of microorganisms 20 to minerals is an important step. For example, bacterium A. ferrooxidans must adhere to the mineral before leaching it in the direct bio-oxidation mechanism (Schaechter, 2009); in bioflotation it has been shown that adhesion is part of the pyrite bio-depression mechanism (Donati et al, 2007;Ohmura et al, 1993).…”