Kim, Hyunjung 1,* ; Kim, Gahee 1 ; Choi, Junhyun 1 ; Choi, Siyoung Q.
2 ; Song, Youngsoo 1 ;
1 Department of Mineral Resources and Energy Engineering, Chonbuk National University, 567, Baekjedaero, Deokjin-gu, Jeonju, Jeonbuk 556-756, Republic of Korea
2 Department of Chemical and Biomolecular Engineering, KAIST, Daejeon, 305-701, Republic of Korea
* Corresponding author. Tel.: +82 (63) 270-2370; fax: +82 (63) 270-2366
E-mail address: kshjkim@jbnu.ac.kr
ABSTRACT
The effects of the bacterial growth phase on the malachite flotation were investigated in a wellcontrolled Hallimond tube system. Rhodococcus opacus , which is one of representative hydrophobic bacteria, was employed for this study. The test results showed that the bacteria in the stationary phase exhibit two-fold greater floatability than those in mid-exponential phase. To understand the observed flotation behavior, complementary cell characterization tests (e.g., zeta potential and contact angle measurements) and cell attachment/detachment tests were conducted. Interestingly, cell detachment tests revealed that the amount of cells detached from the malachite surface is greater for the mid-exponential phase than the stationary phase due to the higher fluid drag applied to the cells at the mid-exponential phase, which was explained by the differences in the size and shape of attached bacteria onto the malachite surface. Specifically, the bacteria in the mid-exponential phase had a larger size and formed loosely-packed structures like an end-to end on the malachite surface.
To investigate the malachite grade and recovery from the complex system which is malachitesilica mixture on scale-up bioflotation using cells for stationary phase. The concentration of malachite was fixed to 10, 20, 30 and 40 wt%. The flotation test results showed that the malachite was selectively floated from malachite-silica mixture. These findings from this study suggest that an ability of selective bioflotation in scale-up system.
Figure 1. The recovery of malachite using mid-exponential and stationary cells with varying cell concentrations (a) and malachite grade and recovery from complex system with 1×10 8 cells/mL of R. opacus cells (b).
KEYWORDS
Bioflotation, Rhodococcus opacus , Bacterial growth phase, Detachment, Malachite-silica system