The mechanism of the sodalite-to-cancrinite phase transformation in synthetic spent Bayer liquor

Barnes, Mark C.; Addai‐Mensah, Jonas; Gerson, Andrea R.

doi:10.1016/s1387-1811(99)00079-7

Cited by 132 publications

(100 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The x-ray diffraction (XRD) results confirmed that two of the most common phyllosilicates in the sediment, smectite and biotite, underwent dissolution, while clinochlore was resistant to weathering under these conditions (Qafoku et al 2003c). The XRD, scanning electron microscope (SEM), and energy-dispersive x-ray spectroscopy (EDS) analyses and measurements demonstrated the formation of aluminosilicate, such as NO 3 -cancrinite with a yarn-like morphology (Anthony et al 1995;Bickmore et al 2001), sodalite with a cotton-ball like morphology (Barnes et al 1999b), and zeophyllite (with a platy morphology). Zeophyllite was formed in the presence of high aluminum concentrations.…”

Section: 7mentioning

confidence: 99%

Remediation of Uranium in the Hanford Vadose Zone Using Ammonia Gas: FY 2010 Laboratory-Scale Experiments

Szecsody¹,

Truex²,

Zhong³

et al. 2010

View full text Add to dashboard Cite

Executive SummaryThis investigation is focused on refining an in situ technology for vadose zone remediation of uranium by the addition of ammonia (NH 3 ) gas with no addition of water. The objectives were to: a) refine the technique of ammonia gas treatment, b) identify the geochemical changes in uranium surface phases, c) identify broader geochemical changes that occur, and d) predict and test injection of ammonia gas for intermediate-scale systems to identify process interactions that could impact field-scale implementation. For ammonia gas injection into vadose zone sediments to be successful as a uranium remediation technology, it needs to show decreased U mobility of the most mobile U phases (aqueous, adsorbed) in a variety of field conditions. Uranium is present in Hanford sediment include in multiple phases including aqueous U(VI)-carbonate complexes, adsorbed, uranium coprecipitated with carbonates, and U-bearing minerals Na-boltwoodite and uranophane. Ammonia treatment of sediments raises the pH in Hanford sediments from 8.0 to 11-13, which has resulted in a decrease in uranium mobility, as evidenced by decrease in aqueous and adsorbed uranium in 85% of the different sediments tested (different U surface phase distributions or NH 3 treatments) and an increase in 8M HNO 3 extracted U (hard to extract U phases, silicates/phosphates/oxides) for 79% of sediments tested. There were also inconsistent changes in two acetate extractions, likely the result of dissolution of multiple surface U phases (U-carbonates, Na-boltwoodite, uranophane). Surface phase analysis by laser induced fluorescence spectroscopy and extended x-ray absorption structure has showed essentially no U surface mineral change in sediments initially containing Na-boltwoodite, but some U surface phase changes in U-calcite coprecipitates to uranyl oxyhydroxide, Na-boltwoodite, and uranyl tricarbonate. Therefore, the ammonia gas treatment appears most effective for U present in the most mobile phases: aqueous U, adsorbed U, and carbonate associated U. NH 3 -treated sediments containing Na-boltwoodite and uranophane showed decreased leaching even though solid phase analysis showed little changes in the U mineralogy. The decreased leaching may be the result of other mineral precipitates coating these phases. Minerals that leached the most significant mass of ions were montmorillonite, muscovite, and kaolinite. A greater understanding of these dissolution/precipitation/coating processes is needed to predict the long-term impact on uranium mobility.Ammonia gas injection experiments conducted in 20-to 30-ft long 1-D systems and a layered 2-D radial flow system were used to characterize the physicochemical changes at the NH 3 reaction front and treatment coverage in heterogeneous sediments. For 5% NH 3 (95%N 2 ) injection, an average of 234 pore volumes were needed to achieve the elevated pH (10.2 to 11.4) of the reaction front observed, with 465 pore volumes needed to achieve pH equilibrium (pH = 11.88), at 4% water content and 35% porosity. The des...

show abstract

Section: 7mentioning

confidence: 99%

Remediation of Uranium in the Hanford Vadose Zone Using Ammonia Gas: FY 2010 Laboratory-Scale Experiments

Szecsody¹,

Truex²,

Zhong³

et al. 2010

View full text Add to dashboard Cite

show abstract

“…The aging of zeolites to their structurally related feldspathoid minerals, the sodalites and cancrinites, is also a well known and well-understood phenomena. 21,22 Ostwald's rule of successive transformation demonstrates that the products found at the longest times represent phases which are thermodynamically more stable under the synthesis conditions than their predecessors. 20 This is in agreement with the known fact that zeolites of the chabzite type (Al 2 O 3 :8SiO 2 ) are the stable phase in ~200% excess NaOH while the denser dewatered sodalites (Al 2 O 3 :2SiO 2 ) are the stable phase in ≥300% excess NaOH at temperatures ≤100°C.…”

Section: Zeolite Aging Mechanismsmentioning

confidence: 99%

Impact of Zeolite Transferred from Tank 19F to Tank 18F on DWPF Vitrification of Sludge Batch 3

Jantzen¹

2004

View full text Add to dashboard Cite

“…This is independent of the route of formation of the gel. Whether the NAS gel forms from solution via a hydrogel process or whether it forms from a sol (solid particles in liquid) 16 via a sol-gel process, the aging sequence of the NAS gel to denser sodalite and still denser cancrinite type species will typically follow an aging path such as that shown in Figure 2 according to Barnes, Mensah and Gerson 17 and Gerson and Zheng. 18 Note that the densification of the phases agrees with the following literature:…”

Section: The Role Of Kinetics In Thermodynamic Modelingmentioning

confidence: 99%

Thermodynamic Modeling of the SRS Evaporators: Part III. Temperature, Evaporation, and Composition Effects on Process Control Strategy

Jantzen¹

2002

View full text Add to dashboard Cite

The mechanism of the sodalite-to-cancrinite phase transformation in synthetic spent Bayer liquor

Cited by 132 publications

References 15 publications

Remediation of Uranium in the Hanford Vadose Zone Using Ammonia Gas: FY 2010 Laboratory-Scale Experiments

Remediation of Uranium in the Hanford Vadose Zone Using Ammonia Gas: FY 2010 Laboratory-Scale Experiments

Impact of Zeolite Transferred from Tank 19F to Tank 18F on DWPF Vitrification of Sludge Batch 3

Thermodynamic Modeling of the SRS Evaporators: Part III. Temperature, Evaporation, and Composition Effects on Process Control Strategy

Contact Info

Product

Resources

About