Bioflotation of malachite using different growth phases of Rhodococcus opacus: Effect of bacterial shape on detachment by shear flow

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We study the effects of the growth phase of Rhodococcus opacus on the floatability of malachite. We find that bacteria in stationary phase show more than two-fold higher floatability than bacteria in mid-exponential phase. To understand the mechanism of this higher floatability for the stationary phase, we examine bacteria surface properties such as zeta potential and contact angle. Surprisingly, all bacteria surface properties are nearly the same; moreover, the amounts of bacteria adsorbed onto malachite are also identical. Despite bacteria's similar surface properties, we discover that the amount of bacteria detached from malachite during the mixing process in flotation is larger for the mid-exponential phase than for the stationary phase. We attribute this to hydrodynamic shear stress due to the fluid flow established in mineral mixing. Furthermore, we observe that bacteria-bacteria interactions are far more significant for the mid-exponential phase, leading to end-to-end aggregation and thus allowing unique loosely-packed structures on the malachite surface to form. Such loose structures of bacteria on the mineral are highly susceptible to fluid flow and can be easily detached from the mineral surface. Our findings suggest that due to the relatively large size of the bacteria, it is crucial to consider the detachment of adhered bacteria on the mineral surface due to fluid flow during mixing, which is easily ignored in typical flotation processes.
Publisher
ELSEVIER SCIENCE BV
Issue Date
2015-10
Language
English
Article Type
Article
Keywords

THIOBACILLUS-FERROOXIDANS; BACILLUS-SUBTILIS; ESCHERICHIA-COLI; AQUEOUS-SOLUTION; FLOTATION; ADHESION; MINERALS; FLOCCULATION; INDUSTRIAL; SULFIDE

Citation

INTERNATIONAL JOURNAL OF MINERAL PROCESSING, v.143, pp.98 - 104

ISSN
0301-7516
DOI
10.1016/j.minpro.2015.09.012
URI
http://hdl.handle.net/10203/205246
Appears in Collection
CBE-Journal Papers(저널논문)
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