ARPHA Conference Abstracts : Conference Abstract
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Conference Abstract
Microbial reduction of synthetic Biogenic Iron Oxides containing various amounts of Organic Carbon and Silica
expand article infoDaniela Quintero‡, Danielle Fortin‡
‡ University of Ottawa, Department of Earth and Environmental Sciences, Faculty of Science, Ottawa, Canada
Corresponding author: Daniela Quintero (dquin020@uottawa.ca)
Received: 12 Jul 2023 | Published: 17 Oct 2023
© 2023 Daniela Quintero, Danielle Fortin
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation: Quintero D, Fortin D (2023) Microbial reduction of synthetic Biogenic Iron Oxides containing various amounts of Organic Carbon and Silica. ARPHA Conference Abstracts 6: e109448. https://doi.org/10.3897/aca.6.e109448
 Open Access

Abstract

Iron oxides formed in close association with bacteria are referred to as biogenic minerals (BIOS). Both the organic part of BIOS and the iron oxide particles affect the net surface charge of those iron-organic carbon aggregates and offer reactive sites that can immobilize many soluble contaminants (Warren and Haack 2001) making BIOS a contender in bioremediation technologies. However, before using BIOS in bioremediation, it is essential to understand the interactions of impurities such as organic matter and other minor components (including silica) (Dyer et al. 2010). This project involves the synthesis of Biogenic Iron Oxides (BIOS) using various silica contents and different soluble alginate concentrations (as an analogue for bacterial exopolysaccharides) close to natural environmental conditions. The mineralogical, chemical and physical composition of the synthesized samples was determined by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Field Emission Scanning Electron Microscopy (FESEM), Fourier-transform Infrared Spectroscopy (FTIR), and with a Malvern Zetasizer Nano instrument. The various samples (mainly ferrihydrite) were then reduced in the presence of Shewanella putrefaciens CN32, a well-known iron reducing bacterium. All microbial reduction experiments (see Table 1) with different types of BIOS were performed under anoxic conditions.

Table 1.
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Percentage of the reduced Fe and linear reduction rates for BIOS containing different molar ratios of organic matter and silica to Fe(III) in hydrous Fe oxides (HFO).

Sample

Maximum Fe Reduced (%) /day

Reduction Rate (day-1)

R2

HFO

1.9

0.026±0.005

0.998

Alginate HFO 0.03

2.29

0.027±0.001

0.953

Alginate HFO 0.04

4.18

0.037 ±0.005

0.953

Alginate HFO 0.05

2.14

0.016±0.001

0.970

Alginate HFO 0.06

1.26

0.016±0.002

0.967

Silicate HFO 0.001

2.2

0.028±0.003

0.963

Silicate HFO 0.005

2.9

0.021±0.002

0.950

Silicate HFO 0.01

1.2

0.014±0.001

0.985

Silicate HFO 0.05

2.8

0.047±0.006

0.949

Silicate HFO 0.1

4.5

0.026±0.003

0.946

Alginate 0.03 + Silica 0.05 HFO

3.95

0.048 ±0.005

0.977

Alginate 0.03+ Silica 0.001 HFO

3.8

0.030±0.002

0.982

Alginate 0.03+ Silica 0.005 HFO

4.5

0.028 ± 0.003

0.951

Alginate 0.03+ Silica 0.1 HFO

4.7

0.047±0.001

0.998

Results indicate that the ratio of organic matter and silica to Fe (III) in BIOS affects the reduction rate. It is proposed that alginate binds to iron oxide particles and protects them from reduction. However, samples in presence of high concentration of silica (i.e.,> 0.05) showed structural disorder which likely prevented nucleation of well ordered ferrihydrite, which in return increased their rate of reduction. In addition, higher reduction rates of ferrihydrite were reported at higher concentrations of silica in BIOS, even in the presence of alginate.

Keywords

Ferrihydrite, Alginate, Silicate, coprecipitation, Reduction, Shewanella CN32

Presenting author

Daniela Quintero

Presented at

Oral Presentation, Part 4: Emerging Tools & Areas of Scientific Inquiry. Theme: Microbial geochemistry and geomicrobiology. Microbe-mineral interactions

Hosting institution

University of Ottawa

Conflicts of interest

The authors have declared that no competing interests exist.

References

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