Incorporation of Chromate into Calcium Carbonate Structure During Coprecipitation

Hua, Bin; Deng, Baolin; Thornton, Edward C.; Yang, John; Amonette, James E.

doi:10.1007/s11270-006-9242-7

Cited by 64 publications

(59 citation statements)

References 20 publications

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“…Chen, Okudan & Riley (2010) found that CaCO 3 produced by Proteus mirabilis had an unusual morphology and structure, mainly formed by vaterite spheres. CaCO 3 precipitation by a mixture of Ca 2+ and CO 3 -2 involves three steps as follows: 1) amorphous calcium carbonate formation with low stability and solubility, 2) their transformation into vaterite, and 3) obtaining calcite which is the most stable solid state of CaCO 3 (Hua, Deng, Thornton, Yang & Amonette, 2007;Shen et al, 2006;Spanos & Koutsoukos, 1998;Wei, Shen, Zhao, Wang & Xu, 2003).…”

Section: Calcium Carbonate Crystalsmentioning

confidence: 99%

Soil bacteria that precipitate calcium carbonate: mechanism and applications of the process

Acuña¹,

Becerra²,

Martínez³

et al. 2018

Acta Agron.

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Bacteria with ureasic activity are microorganisms found in soil that in presence of urea and calcium, they can produce calcium carbonate, a process known as microbiologically induced calcium carbonate precipitation (MICP). This article discusses this process and its mechanism, as well as bacterial urease, calcium carbonate crystals formed, and factors that affect the efficiency of MICP, as type of bacteria, bacterial cell concentrations, pH, temperature and calcium and urea concentrations. In addition, applications as removal of heavy metals in water, bioconsolidation, biocement and CO 2 sequestration are also discussed.Keywords: Biomineralization; Bacillus; urease; carbonates; heavy metals; bioconsolidation; biocementation. ResumenLas bacterias con actividad ureásica son microorganismos que se encuentran en el suelo, y que en presencia de urea y calcio, pueden producir carbonato de calcio, proceso conocido como precipitación de calcio inducida microbiológicamente (PCIM). Este artículo trata este proceso y su mecanismo, además de las ureasas de origen bacteriano, los cristales de carbonato de calcio formado, los factores que afectan la eficiencia la PCIM, como el tipo de bacteria, las concentraciones de células bacterianas, el pH, la temperatura y las concentraciones de calcio y urea. Además, se incluye las aplicaciones como la remoción de metales pesados en aguas, la bioconsolidación, biocemento y secuestro de CO 2 .

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Section: Calcium Carbonate Crystalsmentioning

confidence: 99%

Soil bacteria that precipitate calcium carbonate: mechanism and applications of the process

Acuña¹,

Becerra²,

Martínez³

et al. 2018

Acta Agron.

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“…In contrast, the reductive capacity of Portland cement measured by the Cr(VI) method was an order of magnitude higher than that measured by the Ce(IV) method. This result could be attributed to the precipitation of Cr-bearing phases or coprecipitation of Cr(VI) with CaCO 3 formed at alkaline pH during the reaction with Portland cement powder with the bicarbonate buffer solution used in the Cr(VI) method (Hua et al 2007;Tang et al 2007). The removal of Cr(VI) by such precipitation mechanism, rather than the "pure" reduction of Cr(VI) to Cr(III), results in overestimated reductive capacity.…”

Section: Discussionmentioning

confidence: 99%

“…On the other hand, the reductive capacity of Portland cement measured by the Cr(VI) method was 0.349 meq/g, which was an order of magnitude higher than the reductive capacity measured by the Ce(IV) method. This high reductive capacity of Portland cement determined by the Cr(VI) method could result from the coprecipitation of Cr(VI) with CaCO 3 formed at alkaline pH during the 7-day reaction with Portland cement powder (Hua et al 2007;Tang et al 2007), not from the reduction of Cr(VI) to Cr(III) only. A previous study also reported that Cr-bearing phases such as CaCrO 4 and CaCrO 4 •2H 2 O were formed at alkaline pH (10.5-12.2) during the reaction of Portland cement with high-Cr-concentration solution (15,000-50,000 mg/L) (Laforest and Duchesne 2005), suggesting that the high reductive capacity of Portland cement determined by the Cr(VI) method could be overestimated by the precipitation of Cr-bearing phases.…”

Section: Reductive Capacity Of Dry Ingredientsmentioning

confidence: 95%

Characterization of Technetium Speciation in Cast Stone

Um¹,

Jung²,

Wang³

et al. 2013

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Executive SummaryThis report describes the results from laboratory tests performed at Pacific Northwest National Laboratory (PNNL) for the U.S. Department of Energy (DOE) EM-31 Support Program (EMSP) subtask, "Production and Long-Term Performance of Low Temperature Waste Forms" to provide additional information on technetium (Tc) speciation characterization in the Cast Stone waste form. To support the use of Cast Stone as an alternative to vitrification for solidifying low-activity waste (LAW) and as the current baseline waste form for secondary waste streams at the Hanford Site, additional understanding of Tc speciation in Cast Stone is needed to predict the long-term Tc leachability from Cast Stone and to meet the regulatory disposal-facility performance requirements for the Integrated Disposal Facility (IDF). Characterizations of the Tc speciation within the Cast Stone after leaching under various conditions provide insights into how the Tc is retained and released. The data generated by the laboratory tests described in this report provide both empirical and more scientific information to increase our understanding of Tc speciation in Cast Stone and its release mechanism under relevant leaching processes for the purpose of filling data gaps and to support the long-term risk and performance assessments of Cast Stone in the IDF at the Hanford Site.Various formulations of Cast Stone that include secondary waste simulants and different LAW simulants have been characterized previously. For this report, smaller Cast Stone monoliths were prepared with high Tc concentrations spiked into the 7.8 M Na overall average LAW simulant using dry ingredients from two different sources (referred to as NW and SE). These small Cast Stone monoliths were used for this Tc speciation characterization. The following subtasks are included within the Tc speciation characterization task:1. Measure the reductive capacity of different types of dry ingredients, the 8 LAW simulants used in Westsik et al. (2013), and short-term cured Cast Stone before and after leaching with different leaching conditions. The reductive capacities of dry ingredients from NW and SE sources, various LAW simulants, and final Cast Stone before and after leaching tests were measured using two different methods, the Ce(IV) and Cr(VI) methods. One type of blast furnace slag (BFS) and the high-Ca fly ash were obtained from LaFarge North America Inc. in Pasco, Washington, and these materials are referred to as the NW slag and fly ash. The second BFS and the low-Ca fly ash are the same materials used in the Saltstone processing facility at the Savannah River Site in South Carolina and are referred to as the SE materials. Much more of the solids dissolve in the strong acid (pH ~1-2) environment created by the Ce(IV) method compared to circumneutral pH (~7.0) condition created by the Cr(VII) method. Among the dry ingredients, the reductive capacity measured by the Ce(IV) method was the highest for BFS (0.793 meq/g for NW slag and 0.800 meq/g for SE slag). The reductive ...

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“…The formation of CaCO3 templates with embedded Tinuvin 1130 and Tinuvin 292 was obtained by the coprecipitation (Figure 3) of CaCl2 and Na2CO3 salts [20]. CaCO3 templates were prepared by mixing equal volume of Na2CO3 (1 M) and CaCl2 (1 M) solutions under magnetic stirring for 1 h. 0.1 g of concentrated commercial solution of Tinuvin 1130 or Tinuvin 292 was added to the CaCl2 solution prior to the mixing with the Na2CO3 solution.…”

Section: Synthesis Of Caco3 Templates With Tinuvin 1130 and Tinuvin 292mentioning

confidence: 99%

Effect of Adding UV Absorbers Embedded in Carbonate Calcium Templates Covered with Light Responsive Polymer into a Clear Wood Coating

et al. 2018

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Abstract:The limited durability of clear coatings is a major issue for the coating and wood industry. The addition of organic UV absorbers improves coating resistance by the absorption and the conversion of the UV radiation into harmless heat. Organic UVAs are prone to degradation and can migrate in the binder of coatings. In this study, commercial UVAs and HALS have been entrapped into CaCO 3 templates coated with stimuli responsive polymers. Microspheres were incorporated into a clear acrylic water-based coating formulation. The formulation was applied on glass and wood panels and was placed into an artificial UV chamber. This study presents a comparison between the aesthetic behavior of coating formulations with free and encapsulated commercial UVAs and HALS during the accelerated ageing test. Encapsulation of UVAs was confirmed by XPS and TGA analysis. Results have shown that the coating's aesthetic was slightly improved when using the encapsulated products.

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Incorporation of Chromate into Calcium Carbonate Structure During Coprecipitation

Cited by 64 publications

References 20 publications

Soil bacteria that precipitate calcium carbonate: mechanism and applications of the process

Soil bacteria that precipitate calcium carbonate: mechanism and applications of the process

Characterization of Technetium Speciation in Cast Stone

Effect of Adding UV Absorbers Embedded in Carbonate Calcium Templates Covered with Light Responsive Polymer into a Clear Wood Coating

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