Transmission Electron Microscopy and Nuclear Magnetic Resonance Studies of Geopolymers for Radioactive Waste Immobilization

Blackford, Mark G.; Hanna, John V.; Pike, Kevin J.; Vance, E. R.; Perera, D. S.

doi:10.1111/j.1551-2916.2007.01532.x

Cited by 87 publications

(57 citation statements)

References 33 publications

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“…observations of Blackford et al (2007). It is of interest that no crystalline zeolites are observed in any samples, even for these samples with relatively high water content after 100 days' moist curing; this correlates with the observations of Provis et al (2005) that zeolite formation is notable only at low soluble silicate content for samples cured at moderate temperatures.…”

Section: Degrees 2θsupporting

confidence: 75%

“…Fig. 2b shows that the Sr-containing samples display somewhat more complex behaviour; in particular, insoluble SrCO 3 forms in all Sr-containing samples as previously noted for the nitrate case (Blackford et al, 2007). Even the sample where Sr was added as the relatively insoluble SrSO 4 (K sp = 2.…”

Section: Instrumental Analysismentioning

confidence: 72%

“…Initial work over a decade ago showed some potentially promising results (Davidovits and Comrie, 1988;Khalil and Merz, 1994), and research since that time has resulted in the development of geopolymer formulations with enhanced performance in caesium and strontium immobilisation (Bao et al, 2005;Fernández-Jiménez et al, 2005;Perera et al, 2006;Vance et al, 2006;Berger et al, 2007). The physicochemical and structural roles played by Cs + and Sr 2+ within the geopolymer binder structure were also recently studied in detail by Blackford et al (2007). Cs + was observed to participate to a significant extent in the process of geopolymerisation, acting as a charge-balancing cation within the aluminosilicate network, while Sr 2+ showed a tendency instead to precipitate as insoluble salts.…”

Section: Introductionmentioning

confidence: 95%

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Geopolymerisation kinetics. 3. Effects of Cs and Sr salts

Provis

Walls

Deventer

2008

Chemical Engineering Science

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Section: Degrees 2θsupporting

confidence: 75%

Section: Instrumental Analysismentioning

confidence: 72%

Section: Introductionmentioning

confidence: 95%

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Geopolymerisation kinetics. 3. Effects of Cs and Sr salts

Provis

Walls

Deventer

2008

Chemical Engineering Science

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“…Immobilization of lead by geopolymers has attracted much study, and has been suggested to occur by the chemical formation of an insoluble lead silicate rather than by physical entrapment within the geopolymer pore structure (27 (28). Incorporation of radioactive Sr in the amorphous geopolymer matrix does not occur to any great extent, mostly by the formation of crystalline SrCO 3 rather than in a chargebalancing role (29). All these studies suggest that by analogy with flyash-based geopolymers, the present materials prepared by alkali treatment of milled pond ash might result in the retention of the hazardous elements inside the the geopolymer binder paste, as has been found to be the case.…”

Section: Leaching Of Heavy Metals From the Geopolymersmentioning

confidence: 99%

Properties of geopolymer binders prepared from milled pond ash

et al. 2017

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Alkali-activated materials were prepared from pond ash from the Darkhan city (Mongolia) thermal power station. This ash contains about 60 wt % X-ray amorphous material in addition to quartz, mullite, hematite and magnesioferrite, and presents significant storage problems since it is accumulating in large amounts and is a hazardous waste, containing 90-100 ppm of the heavy metals As, Pb and Cr, and about 800 ppm Sr. Alkali-activated materials synthesized from the as-received pond ash achieved compressive strengths of only 3.25 MPa. Reduction of the particle size by mechanical milling for up to 30 min progressively increases the compressive strength of the resulting alkali-activated geopolymer up to 15.4 MPa. Leaching tests indicate that the combination of milling and alkali treatment does not cause the release of the hazardous heavy metals from the product, making it suitable for construction applications. RESUMEN: Propiedades de geopolímeros preparados a partir de cenizas de estanque.Se prepararon materiales activados alcalinamente a partir de cenizas de charca de la central térmica de Darkhan (Mongolia). Esta ceniza contiene alrededor de un 60% en peso de material amorfo además de mullita, hematita, cuarzo y magnesioferrite. Presenta además importantes problemas de almacenamiento ya que se acumula en grandes cantidades y es un desecho peligroso, que contiene entre 90-100 ppm de metales pesados como Pb y Cr, y alrededor de 800 ppm de Sr. Los materiales sintetizados a partir de las cenizas de estanque presentaron resistencias a compresión de tan sólo 3,25 MPa. La reducción del tamaño de partícula por fresado mecánico hasta 30 min aumentó las resistencias mecánicas hasta valores de 15.4 MPa. Las pruebas de lixiviación indican que la combinación de molienda y activación alcalina no causan la liberación de los metales pesados peligrosos del producto, por lo que resulta adecuado para aplicaciones en construcción.PALABRAS CLAVE: Cenizas de estanque; Molienda; Cementos activados alcalinamente; Resistencias a compresión; Microstructura ORCID ID: J. Temuujin

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“…The soil mineral dissolution followed the order of quartz fi kaolinite fi illite, and although cancrinite, sodalite, and zeolite were formed, the zeolite was not detected after 25 days of reaction time (Mashal et al 2005a), indicating that this mineral underwent either dissolution or phase transformation. Other relevant references follow: Gerson and Zheng 1997;Hassan 1997;Zheng et al 1997;Barnes et al 1999a;Green-Pedersen and Korshin 1999;Park and Englezos 1999;Buhl et al 2000;Buck and McNamara 2004;Zhao et al 2004;Bao et al 2005;Blackford et al 2007;Chorover et al 2008;and Leyva-Ramos et al 2008. 3.1…”

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

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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...

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Transmission Electron Microscopy and Nuclear Magnetic Resonance Studies of Geopolymers for Radioactive Waste Immobilization

Cited by 87 publications

References 33 publications

Geopolymerisation kinetics. 3. Effects of Cs and Sr salts

Geopolymerisation kinetics. 3. Effects of Cs and Sr salts

Properties of geopolymer binders prepared from milled pond ash

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

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