Geochemical evaluation of uranium sequestration from field-scale infiltration and injection of polyphosphate solutions in contaminated Hanford sediments

From EXAFS of reference compounds to U(VI) speciation in contaminated environments

“…Uranium speciation in contaminated soils, groundwater, vadose zones and bottom sediments of waste storage pools governs the migration behavior in plumes of mine tailings and legacy sites of nuclear weapon production (Zachara et al, 2013;Peterson et al, 2018;Kaplan et al, 2020;Stetten et al, 2020). Decommissioning of closed enterprises and decontamination of territories require knowledge of U species to predict U migration in the environment (Maher et al, 2013;Mehta, 2017;Katsenovich et al, 2018). The complexity of U behavior in the environment due to the presence of carbonates, organic matter, Fe oxides, bacterial activity etc.…”

Phosphate (Bio)mineralization Remediation of 90Sr-Contaminated Groundwaters

“…The polyphosphate experiments were conducted with 10 mM polyphosphate consisting of 90% orthophosphate (mixture of KH 2 PO 4 , K 2 HPO 4 , NaH 2 PO 4 , and Na 2 HPO 4 ) and 10% pyrophosphate (Na 4 P 2 O 4 ), which was added to the PPQ and CR microcosms. 24 Once spiked with the appropriate amendments, flasks (500 mL) were capped with porous foam bungs to maintain an oxic headspace in equilibration with laboratory air and stored under dark conditions at room temperature for 31 days, with gentle swirling at least twice per week to an avoid excessive abrasion consistent with past studies. 8,40 All experiments were run in triplicate and sediment-only controls with 1 mM (88 ppm) Sr 2+ were also prepared.…”

“…For the glycerol phosphate amended system, 10 mM filter sterilized glycerol phosphate was spiked into the PPQ and CR microcosms. The polyphosphate experiments were conducted with 10 mM polyphosphate consisting of 90% orthophosphate (mixture of KH 2 PO 4 , K 2 HPO 4 , NaH 2 PO 4 , and Na 2 HPO 4 ) and 10% pyrophosphate (Na 4 P 2 O 4 ), which was added to the PPQ and CR microcosms …”

“…7,28,29 Abiotic mineralization approaches have also been investigated at the Hanford nuclear site, using polyphosphate amendment solutions to remediate U-contaminated land. 24 Here, a mix of readily available orthophosphate (PO 4 ) was injected into the subsurface to promote Ca-phosphate mineral precipitation. 24,30,31 When injected, the reaction between groundwater Ca 2+ (aq) and orthophosphates formed low solubility U-bearing calcium phosphate phases.…”

“…Abiotic mineralization approaches have also been investigated at the Hanford nuclear site, using polyphosphate amendment solutions to remediate U-contaminated land . Here, a mix of readily available orthophosphate (PO 4 3– ) and less available pyrophosphate (P 2 O 7 4– ) was injected into the subsurface to promote Ca-phosphate mineral precipitation. ,, When injected, the reaction between groundwater Ca 2+ (aq) and orthophosphates formed low solubility U-bearing calcium phosphate phases. Ongoing precipitation of Ca-phosphates was then thought to be sustained by slow hydrolysis of the pyrophosphate, liberating additional orthophosphate which further reacted with aqueous Ca 2+ enabling Ca-phosphate precipitation within a wider area of the subsurface…”