Presentation Information
[P02-251]Sponge-Based Immobilization of Acidithiobacillus ferrooxidans for Localized Iron Compound Synthesis and Selenate Removal
○Upasana Jhariya1, Mei-Fang CHIEN1, Masaki UMETSU1, Masanobu KAMITAKAHARA1 (1. Graduate School of Environmental Studies, Tohoku University (Japan))
Keywords:
Immobilization,Iron-based compounds,Acidithiobacillus ferrooxidans,Selenate,Wastewater
Microbial synthesis of iron compounds using Acidithiobacillus ferrooxidans offers a sustainable alternative to chemical methods. These biogenic iron compounds act as reactive adsorbent for heavy metals (HMs) contaminated wastewater. However, conventional synthesis presents challenges in separating the adsorbents after treatment.
When iron compounds were synthesized directly from solid iron plates, the precipitates dispersed throughout the solution. This uncontrolled dispersion complicates recovery. It may also cause the release of bacteria and heavy metal–adsorbed particles into the treated effluent. Therefore, a localized and easy to filter iron compound synthesis system is needed.
To address this limitation, we explored a localized synthesis strategy using bacterial immobilization. Three immobilization methods were tested: alginate, polyvinyl alcohol (PVA), and sponge matrices. Alginate and PVA were applied around the iron plate to prevent mineral release. Initial iron oxidation was observed. However, both polymers partially dissolved under acidic conditions. As a result, the synthesized iron compounds were released into the medium. These systems failed to maintain structural stability.
In contrast, sponge-based immobilization, where bacteria were growing to the sponge matrix, maintained structural integrity throughout the process. The sponge provided stable support for bacterial growth and enabled confined iron compounds deposition without leaking into the surrounding medium. Mineralogical characterization using X-ray diffraction confirmed the formation of jarosite and schwertmannite, while scanning electron microscopy revealed fine acicular particles with high surface area. Selenate removal experiments showed approximately 34% removal at an initial concentration of 0.2 mM within 72 hours, as measured by ICP-MS.
This study demonstrates that sponge immobilization enables stable, localized, and recoverable iron compounds synthesis. It provides a practical solution to overcome separation challenges in wastewater treatment systems.
When iron compounds were synthesized directly from solid iron plates, the precipitates dispersed throughout the solution. This uncontrolled dispersion complicates recovery. It may also cause the release of bacteria and heavy metal–adsorbed particles into the treated effluent. Therefore, a localized and easy to filter iron compound synthesis system is needed.
To address this limitation, we explored a localized synthesis strategy using bacterial immobilization. Three immobilization methods were tested: alginate, polyvinyl alcohol (PVA), and sponge matrices. Alginate and PVA were applied around the iron plate to prevent mineral release. Initial iron oxidation was observed. However, both polymers partially dissolved under acidic conditions. As a result, the synthesized iron compounds were released into the medium. These systems failed to maintain structural stability.
In contrast, sponge-based immobilization, where bacteria were growing to the sponge matrix, maintained structural integrity throughout the process. The sponge provided stable support for bacterial growth and enabled confined iron compounds deposition without leaking into the surrounding medium. Mineralogical characterization using X-ray diffraction confirmed the formation of jarosite and schwertmannite, while scanning electron microscopy revealed fine acicular particles with high surface area. Selenate removal experiments showed approximately 34% removal at an initial concentration of 0.2 mM within 72 hours, as measured by ICP-MS.
This study demonstrates that sponge immobilization enables stable, localized, and recoverable iron compounds synthesis. It provides a practical solution to overcome separation challenges in wastewater treatment systems.
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