149-2 The role of microbial biomass, exudates, and hydrous manganese oxide biominerals in critical metal recovery from acid mine drainage passive remediation systems

Session: Research to Accelerate Recovery of Critical Minerals from Primary and Secondary Resources (Posters)

Poster Booth No.: 270

Presenting Author:

Aden Boyd

Authors:

Boyd, Aden andru¹, Dzurko, Keegen², Nguyen, Hanna³, Powers, Aubrey⁴, Boothe-Lorden, Tashane⁵, Capo, Rosemary C.⁶, Stewart, Brian W.⁷, Hedin, Benjamin⁸, Hinkle, Margaret A. G.⁹

(1) washington and lee university, washington and lee university, lexington, virginia, USA, (2) Washington and lee earth and environmental geoscience, lexington, virginia, USA, (3) washington and lee earth and environmental geoscience, lexington, virginia, USA, (4) environmental geoscience, washington and lee university, lexington, virginia, USA, (5) Geology and environmental science, University of pittsburgh, pittsburgh, pennsylvania, USA, (6) geology and environmental science, University of Pittsburgh, Pittsburgh, PA, USA, (7) geology and environmental geoscience, University of Pittsburgh, Pittsburgh, PA, USA, (8) Hedin Environmental, bethel park, PA, USA, (9) earth and environmental geoscience department, WLU Earth & Environmental Geoscience, Lexington, VA, USA,

Abstract:

Identifying potential sources of critical metals, such as rare earth elements (REEs), is crucial to the success of the energy transition. Hydrous manganese oxides (HMOs), with their relatively large surface area to volume ratios and highly reactive surfaces, can concentrate critical metals in economically viable amounts via adsorption and coprecipitation processes. Acid mine drainage (AMD) passive remediation sites, designed to increase pH and remove toxic metals, often contain high concentrations of manganese, REEs, and yttrium in the aqueous phase at low pH conditions. As the treatment system pH increases, the aqueous concentrations of these critical metals decrease but manganese persists, with the last step focused on HMO precipitation, often facilitated by manganese-oxidizing microbes. Deploying these freshly precipitated HMOs upstream in the treatment system to concentrate REEs and yttrium holds promise as a sustainable critical metal extraction method. With this research, we explore REE and yttrium reactions with microbial biomass, exudates, and HMO biominerals to better understand the potential role of manganese-oxidizing microbes in critical metal recovery from AMD. Two manganese-oxidizing fungi with different oxidation behaviors were investigated: Stagonospora sp. SRC1lsM3a and Paraphaeosphaeria sporulosa AP3s5-JAC2a. REE binding during manganese oxidative precipitation in the presence of fungal biomass and in the presence of fungal cell-free filtrates (i.e., fungal exudates) were explored. In addition, experiments tracking REE aqueous concentrations in manganese-free systems consisting of just biomass and of just the cell-free filtrates were conducted to isolate the role of REE binding to biomass and of reactions between REEs and fungal exudates. We find that due to pH constraints on both manganese oxidative precipitation reactions and on REE stability in the aqueous phase, the ideal pH range for such critical mineral extraction via HMO biomineral coprecipitation reactions is 6-7.5. Manganese oxidation was most rapid in the presence of microbial biomass. Throughout the experiment, aliquots of the solutions were filtered and analyzed via inductively coupled plasma-mass spectrometry for REE and manganese concentrations to track both REE removal from the aqueous phase and manganese oxidation over time. This work will determine the different roles of fungal biomass, HMO biominerals, and fungal exudates in critical metal recovery, a potential solution for both remediating AMD and securing metals essential for the energy transition.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10311

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