Influence of the alkalinity and /Cl− anionic composition on the synthesis of the cancrinite–sodalite system

Ocanto, Freddy; Álvarez, Ruth; Navarro, Caribay Urbina de; Friedrich, Alexandra; Linares, Carlos F.

doi:10.1016/j.micromeso.2008.04.019

Cited by 23 publications

(22 citation statements)

References 12 publications

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“…Literature data on cancrinites and sodalites were gathered, which pointed to sodalite as a more natural fit for the Cl -anion. [31][32][33] Good examples of synthesized cancrinite with Cl -anion were not found in this literature survey; instead, cancrinite was the preferred structure when at least some amount of NO 3 -, CO 3 -, or OH -anion was present.…”

Section: Mineral Literature Surveymentioning

confidence: 86%

“…Many variations of this basic approach were found in the literature. [31][32][33] Leachability data were available in the literature for natural sodalite and iodine sodalite. Sodalite was studied as a waste form for immobilizing the long lived 129 I isotope by Nakazawa et al, who measured a normalized release rate of ~ 10 -4 g/m 2 /d for the synthesized iodine sodalite and ~ 10 -5 g/m 2 /d for the natural sodalite.…”

Section: Mineral Literature Surveymentioning

confidence: 99%

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Alternative Waste Forms for Electro-Chemical Salt Waste

Crum¹,

Sundaram²,

Riley³

et al. 2009

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SUMMARYThis study was undertaken to examine alternative crystalline (ceramic/mineral) and glass waste forms for immobilizing spent salt from the Advanced Fuel Cycle Initiative (AFCI) electrochemical separations process (Echem). The AFCI is a program sponsored by U.S. Department of Energy (DOE) to develop and demonstrate a process for recycling used nuclear fuel (UNF). Echem is a molten salt process for the reprocessing of UNF in an electrorefiner and generates spent KCl-LiCl salt that is contaminated with alkali, alkaline earths, halide, and lanthanide fission products (FP) that must either be cleaned of FP and other contaminants or replaced with new salt to maintain separations efficiency. Currently, these spent salts are occluded on zeolite 4A, mixed with a borosilicate binder, and heat treated to form a glass-bonded mineral waste form. The focus of this study was to investigate alternative waste forms to immobilize spent salt. A condensed version of the calculated composition of a spent salt with 20 mass% fission products is given in Table S1.[1] On a mole basis, the spent salt is dominated by alkali chlorides with minor amounts of alkaline earth and lanthanide chlorides. Borosilicate glass is the most widely studied and accepted waste form for immobilizing radioactive waste. [2][3][4][5] However, the limited solubility of chloride in borosilicate glass leads to low waste loading of spent Echem salt. To address this issue, past work with spent electrochemical salt from the electrochemical processing of sodium-bonded nuclear fuel led to the development of a two-step process that resulted in a glass-bonded ceramic waste form consisting of ~ 75 mass% minerals (primarily sodalite) bonded in a borosilicate glass network.[6] The sodalite allows higher loadings of Cl. The glass matrix encapsulates the sodalite and other minerals, supplies silica for the formation of sodalite, and solubilizes some of the FP and impurities.In the study reported here, we explored glass systems that are more compatible with Cl and have not been previously considered for use as waste forms. In addition, alternate methods were explored with the hope of finding a way to produce a sodalite that is more accepting of as many FP present in the spent salt as possible.This study investigated two different options:1. alternate glass families that incorporate increased concentrations of Cl 2. alternate methods to produce a mineral waste form.A literature survey was conducted for each option to identify high halide-containing glasses and minerals. Available fabrication and characterization methods along with available waste-form performance data were gathered from the available literature and evaluated to determine the best candidate glass systems and mineral structures for scoping studies. Scoping studies were conducted based on the conclusions from the literature surveys. [7] glass standard for high-level waste. However, they show promise and should be further developed by investigating other compositions to achieve optimized glass with improved...

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Section: Mineral Literature Surveymentioning

confidence: 86%

Section: Mineral Literature Surveymentioning

confidence: 99%

Alternative Waste Forms for Electro-Chemical Salt Waste

Crum¹,

Sundaram²,

Riley³

et al. 2009

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“…Based on the literature, sodalite is more likely to form when the only anion present is Cl -are present then cancrinite can become the preferred structure. [4][5][6] Chemistry changes were made in an attempt to form cancrinite in place of sodalite. The additions of NO 3 -, CO 3 2-, and OH -were examined to determine which if any would form cancrinite instead of sodalite, since cancrinite has a higher theoretical waste loading (23 mass%) than sodalite (13 mass%).…”

Section: Tablesmentioning

confidence: 99%

Alternative Electrochemical Salt Waste Forms, Summary of FY2010 Results

Riley¹,

Rieck²,

Crum³

et al. 2010

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SUMMARYIn FY2009, the Pacific Northwest National Laboratory (PNNL) performed scoping studies to down-select two candidate waste forms for spent electrochemical salt, tellurite (TeO 2 -based) glasses and high-halide minerals. Both candidates showed promise with acceptable Product Consistency Test (PCT) responses (i.e., an assessment of chemical durability) and immobilization of at least 10 mass% fission product waste stream. These candidates were investigated in FY2010.Sodalite was successfully synthesized by the sol-gel method. The vast majority of the dried sol-gel consisted of sodalite with small amounts of alumino-silicates and unreacted salt. Upon firing the powders made by sol-gel, the primary phase observed was sodalite with the addition of various amounts of nepheline, carnegieite, lithium silicate, and lanthanide oxides. The amounts of sodalite, nepheline, and carnegieite varied with firing temperature, as did the bulk density of the fired pellets, sol-gel process chemistry, and the amount of glass sintering aid added to the batch. As the firing temperature was increased from 850°C to 950°C, chloride volatility increased, the fraction of sodalite decreased, and the fractions of nepheline and carnegieite increased. This indicates that the sodalite structure is not stable and begins to convert to nepheline and carnegieite under these conditions at 950°C. Density has an inverse relationship with firing temperature. The addition of NBS-1, a borosilicate glass sintering aid, had a positive effect on bulk density and increased the stability of the sodalite structure. A summary data table for FY2010 halide mineral investigations is presented in Table S1.1. Table S1.1. Summary data for FY2010 halide mineral investigations. "WL" denotes the waste loading (in mass%); "Firing T" denotes the firing temperature (in °C); For the Phase Assemblage, "S" denotes sodalite, "N" denotes nepheline + carnegieite, and "L" denotes lithium silicate phases determined by Xray diffraction. NL Na and NL Cl denote the sodium and chlorine normalized release, respectively, from the PCT. At the beginning of FY2010, an in-depth literature review kicked off the tellurite glasses study. The review was aimed at compiling data for chemical durability and mixed chloride incorporation for tellurite glasses. The literature review led the authors to four binary and one ternary systems for further investigation, which include TeO 2 plus the following: PbO, Al 2 O 3 -B 2 O 3 , WO 3 , P 2 O 5 , or ZnO. Each system was studied with and without a mixed-chloride simulated electrochemical salt waste stream, and the literature review provided the starting points for the baseline compositions as well as starting points for melting temperature, compatible crucible types, etc. The most promising glasses in each system were scaled up from 5 g scoping study batches to 20 g batches which were analyzed using the PCT. Both asfabricated samples and samples exposed to PCT were analyzed for phase separation or undissolved materials. Table S1.2 summarizes the result...

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“…22 Com o desenvolvimento de diferentes métodos de síntese, tem-se chegado a sodalitas com uma vasta variedade na composição. [23][24][25][26][27] Com base nas interações entre átomos hospedeiros e átomos hóspedes, sodalitas com diferentes características químicas são descritas, as quais podem pertencer à categoria de feldspatoides, zeólitas ou clatratos. 23 Para os mineralogistas, a sodalita natural com composição típica descrita anteriormente é um feldspatoide, em vez de zeólita, porque não contém água nas cavidades, ocupadas somente por ânions de cloro.…”

Section: Introductionunclassified

“…[23][24][25][26][27] Com base nas interações entre átomos hospedeiros e átomos hóspedes, sodalitas com diferentes características químicas são descritas, as quais podem pertencer à categoria de feldspatoides, zeólitas ou clatratos.…”

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Síntese hidrotermal de sodalita básica a partir de um rejeito de caulim termicamente ativado

Paz¹,

Angélica²,

Neves³

2010

Quím. Nova

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Recebido em 8/3/09; aceito em 1/9/09; publicado na web em 23/2/10 HYDROTHERMAL SYNTHESIS OF BASIC SODALITE FROM A THERMICALLY ACTIVATED KAOLIN WASTE. Basic sodalite was successfully synthesized by hydrothermal method using kaolin waste as source of Aluminum and Silicon. This waste is mainly composed by kaolinite and is produced in large amount by kaolin processing industries for paper coating from the Amazon region. Initially, the waste has been calcined at 700 ºC for 2 h and then reacted with the following solutions: Na 2 CO 3 and mixture of Na 2 CO 3 + NaOH to 150 ºC with autogenous pressure for 24 h. The raw materials and transformed materials were characterized by XRD, FTIR and SEM. In both studied media, well-crystallized, basic sodalite was the only phase synthesized, while in the literature usually a mixture of zeolites is obtained.Keywords: synthesis; basic sodalite; kaolin waste. INTRODUÇÃOA região amazônica dispõe de grandes e valiosos depósitos de caulim que, por sua natureza geológica, são adequados ao seu uso mais nobre, a cobertura de papel. Só no Estado do Pará estão localizadas três grandes indústrias de beneficiamento de caulim do País, que geram de rejeito, somente nas etapas de separação granulométrica e branqueamento, mais de 1 milhão de toneladas por ano e, em função deste elevado volume, faz-se necessária a construção de onerosas lagoas de sedimentação para sua deposição.1-3 O rejeito depositado nas lagoas não apresenta consistência adequada que permita o recobrimento convencional para a recuperação da área, o que o torna um problema ambiental. No entanto, a utilização desse rejeito como matéria-prima na síntese de zeólitas tem-se mostrado bastante viável, 4,5 isso porque tal material é composto essencialmente por caulinita, argilomineral mais empregado como fonte de Si e Al em síntese de zeólita e de material com estrutura relacionada. [6][7][8][9] A caulinita é o principal constituinte do caulim, quimicamente é um silicato de alumínio hidratado, que normalmente se encontra associada a outros minerais sob a forma de impurezas, de modo geral, quartzo, mica, feldspato, óxidos de ferro e titânio. É formada pelo empilhamento regular de camadas 1:1, isto é, cada camada é constituída de uma folha de tetraedros SiO 4 e uma folha de octaedros de Al 2 (OH) 6 ligadas entre si por oxigênios comuns, dando uma estrutura fortemente polar. As ligações entre as camadas são feitas por ligações de hidrogênio, OH-O, uma vez que existe um plano de íons hidroxila numa das faces da camada e um plano de íons oxigênio na outra camada adjacente. A energia de ligação costuma variar para cada espécie, mas no geral é preciso temperaturas entre 500 e 700 ºC para que todas as OH -sejam eliminadas. A fórmula estrutural da cela unitária da caulinita é Al 2 Si 4 O 10 (OH) 8 e a composição percentual: SiO 2 -46,54%, Al 2 O 3 -39,50% e H 2 O -13,96%. 10-13As zeólitas são aluminossilicatos hidratados com uma estrutura cristalina de geometria precisa e nanoporos de tamanho uniforme, formando canais de dimensões moleculares, c...

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Influence of the alkalinity and /Cl− anionic composition on the synthesis of the cancrinite–sodalite system

Cited by 23 publications

References 12 publications

Alternative Waste Forms for Electro-Chemical Salt Waste

Alternative Waste Forms for Electro-Chemical Salt Waste

Alternative Electrochemical Salt Waste Forms, Summary of FY2010 Results

Síntese hidrotermal de sodalita básica a partir de um rejeito de caulim termicamente ativado

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