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Biostimulation as a sustainable solution for acid neutralization and uranium immobilization post acidic in-situ recovery

DOI: 10.1016/j.scitotenv.2022.153597 DOI Help

Authors: Thomas Coral (Ecole Polytechnique Fédérale de Lausanne) , Anne-Laure Placko (Orano Mining) , Daniel Beaufort (Université de Poitiers/CNRS, UMR 7285 IC2MP, Equipe HydrASA) , Emmanuel Tertre (Université de Poitiers/CNRS, UMR 7285 IC2MP, Equipe HydrASA) , Rizlan Bernier-Latmani (Ecole Polytechnique Fédérale de Lausanne) , Michael Descostes (Orano Mining; MINES ParisTech, PSL University) , Hélène De Boissezon (Orano Mining) , Sophie Guillon (MINES ParisTech, PSL University) , Pierre Rossi (Ecole Polytechnique Fédérale de Lausanne)
Co-authored by industrial partner: Yes

Type: Journal Paper
Journal: Science Of The Total Environment

State: Published (Approved)
Published: January 2022
Diamond Proposal Number(s): 13890

Abstract: Major uranium (U) deposits worldwide are exploited by acid leaching, known as ‘in-situ recovery’ (ISR). ISR involves the injection of an acid fluid into ore-bearing aquifers and the pumping of the resulting metal-containing solution through cation exchange columns for the recovery of dissolved U. Rehabilitation of ISR-impacted aquifers could be achieved through natural attenuation, or via biostimulation of autochthonous heterotrophic microorganisms due to the associated acid neutralization and trace metal immobilization. In this study, we analyzed the capacity of pristine aquifer sediments impacted by diluted ISR fluids to buffer pH and immobilize U. The experimental setup consisted of glass columns, filled with sediment from a U ore-bearing aquifer, through which diluted ISR fluids were flowed continuously. The ISR solution was obtained from ISR mining operations at the Muyunkum and Tortkuduk deposits in Kazakhstan. Following this initial phase, columns were biostimulated with a mix of molasses, yeast extract and glycerol to stimulate the growth of autochthonous heterotrophic communities. Experimental results showed that this amendment efficiently promoted the activity of acid-tolerant bacterial guilds, with pH values rising from 4.8 to 6.5–7.0 at the outlet of the stimulated columns. The reduction of sulfate, nitrate, and metals as well as dissimilatory nitrate reduction to ammonia induced the rise in pH values, in agreement with geochemical modelling results. Biostimulation efficiently promoted the complete immobilization of U, with the accumulation of up to 3343 ppm in the first few centimeters of the columns. Synchrotron analysis and SEM-EDS revealed that up to 60% of the injected hexavalent U was immobilized as tetravalent non-crystalline U onto bacterial cell surfaces. 16S rDNA amplicon analysis and qPCR data suggested a predominant role played for members of the Phylum Firmicutes (from the genera Clostridium, Pelosinus and Desulfosporosinus) in biological U reduction and immobilization.

Journal Keywords: Uranium; In-situ recovery; Column experiments; Biostimulation; Microbial communities

Diamond Keywords: Bioremediation; Bacteria

Subject Areas: Earth Science, Chemistry, Environment

Instruments: B18-Core EXAFS

Other Facilities: BL4-1 and BL11-2 at Stanford Synchrotron Radiation Lightsource

Added On: 02/02/2022 09:19

Discipline Tags:

Desertification & Pollution Earth Sciences & Environment Biotech & Biological Systems Biotechnology Radioactive Materials Chemistry Materials Science Engineering & Technology Nuclear Waste Organic Chemistry Geology Life Sciences & Biotech Geochemistry

Technical Tags:

Spectroscopy X-ray Absorption Spectroscopy (XAS) X-ray Absorption Near Edge Structure (XANES)