Behavior of iodate substituted ettringite during aqueous leaching
Ettringite [Ca6Al2(SO4)3(OH)12·26H2O] found in cementitious waste forms (CWFs) is known to immobilize iodate (IO3−) via sulfate (SO42-) substitution; however, limited studies have investigated the effects of leaching on the long-term fate and behavior of IO3− retained in ettringites. In this study,...
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| Veröffentlicht in: | Applied geochemistry 2021-02, Vol.125 (C), p.104863, Article 104863 |
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| creator | Avalos, Nancy M. Varga, Tamas Mergelsberg, Sebastian T. Silverstein, Joshua A. Saslow, Sarah A. |
| description | Ettringite [Ca6Al2(SO4)3(OH)12·26H2O] found in cementitious waste forms (CWFs) is known to immobilize iodate (IO3−) via sulfate (SO42-) substitution; however, limited studies have investigated the effects of leaching on the long-term fate and behavior of IO3− retained in ettringites. In this study, ettringite mineral transformation and iodine release from IO3−-incorporated ettringite ((IO3−)-Ett) were investigated using batch experiments to determine the mechanisms likely to drive IO3− release/retention within ettringite in environmentally relevant solutions of varying composition, pH, and alkalinity. (IO3−)-Ett was leached in six simulated solutions relevant to the Hanford Site (Washington State, USA) for a period of 56 days: double deionized water, 24 ppm CO32-, 1400 ppm SO42-, Hanford groundwater, Hanford vadose zone porewater and a cement-equilibrated solution. By monitoring IO3− uptake and removal and characterizing changes in the solid material, incongruent dissolution of ettringite to calcite and oxyanion substitution into the ettringite structure (e.g., SO42- or CO32-) were identified as contributing IO3− release mechanisms. However, the formation of calcium carbonates, e.g., calcite, may re-incorporate IO3− (pH |
| doi_str_mv | 10.1016/j.apgeochem.2020.104863 |
| format | Article |
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•CO32- and SO42- ions mineralogically transform (IO3−)-incorporated ettringite and cause the release of retained IO3−.•(IO3−)-incorporated ettringites formed at the surface of cement will be susceptible to transformation and IO3− release.•The formation of calcite at pH < 10 may re-immobilize IO3−.•(IO3−)-incorporated ettringite carbonation within cement pore spaces may help retain IO3−.</description><identifier>ISSN: 0883-2927</identifier><identifier>EISSN: 1872-9134</identifier><identifier>DOI: 10.1016/j.apgeochem.2020.104863</identifier><language>eng</language><publisher>United Kingdom: Elsevier Ltd</publisher><subject>Dissolution ; Incorporation/retention by secondary mineral formation ; Mobilization ; Oxyanion substitution ; Radionuclide</subject><ispartof>Applied geochemistry, 2021-02, Vol.125 (C), p.104863, Article 104863</ispartof><rights>2021 Elsevier Ltd</rights><lds50>peer_reviewed</lds50><oa>free_for_read</oa><woscitedreferencessubscribed>false</woscitedreferencessubscribed><citedby>FETCH-LOGICAL-a414t-fdd3c864b14146df14c819cbfc8eb42de90a878e6747039f34f8d7966292ce783</citedby><cites>FETCH-LOGICAL-a414t-fdd3c864b14146df14c819cbfc8eb42de90a878e6747039f34f8d7966292ce783</cites><orcidid>0000-0002-5492-866X ; 0000-0002-8385-2676 ; 0000-0001-8073-4642 ; 0000000180734642 ; 000000025492866X ; 0000000283852676</orcidid></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><linktohtml>$$Uhttps://dx.doi.org/10.1016/j.apgeochem.2020.104863$$EHTML$$P50$$Gelsevier$$H</linktohtml><link.rule.ids>230,314,780,784,885,3550,27924,27925,45995</link.rule.ids><backlink>$$Uhttps://www.osti.gov/biblio/1809642$$D View this record in Osti.gov$$Hfree_for_read</backlink></links><search><creatorcontrib>Avalos, Nancy M.</creatorcontrib><creatorcontrib>Varga, Tamas</creatorcontrib><creatorcontrib>Mergelsberg, Sebastian T.</creatorcontrib><creatorcontrib>Silverstein, Joshua A.</creatorcontrib><creatorcontrib>Saslow, Sarah A.</creatorcontrib><title>Behavior of iodate substituted ettringite during aqueous leaching</title><title>Applied geochemistry</title><description>Ettringite [Ca6Al2(SO4)3(OH)12·26H2O] found in cementitious waste forms (CWFs) is known to immobilize iodate (IO3−) via sulfate (SO42-) substitution; however, limited studies have investigated the effects of leaching on the long-term fate and behavior of IO3− retained in ettringites. In this study, ettringite mineral transformation and iodine release from IO3−-incorporated ettringite ((IO3−)-Ett) were investigated using batch experiments to determine the mechanisms likely to drive IO3− release/retention within ettringite in environmentally relevant solutions of varying composition, pH, and alkalinity. (IO3−)-Ett was leached in six simulated solutions relevant to the Hanford Site (Washington State, USA) for a period of 56 days: double deionized water, 24 ppm CO32-, 1400 ppm SO42-, Hanford groundwater, Hanford vadose zone porewater and a cement-equilibrated solution. By monitoring IO3− uptake and removal and characterizing changes in the solid material, incongruent dissolution of ettringite to calcite and oxyanion substitution into the ettringite structure (e.g., SO42- or CO32-) were identified as contributing IO3− release mechanisms. However, the formation of calcium carbonates, e.g., calcite, may re-incorporate IO3− (pH < 10) or prevent the release of IO3− when formed on solution-exposed surfaces of ettringite. These results provide valuable insights into iodine release from CWFs that may be used to improve current CWF formulations for the treatment of iodine-containing nuclear waste.
[Display omitted]
•CO32- and SO42- ions mineralogically transform (IO3−)-incorporated ettringite and cause the release of retained IO3−.•(IO3−)-incorporated ettringites formed at the surface of cement will be susceptible to transformation and IO3− release.•The formation of calcite at pH < 10 may re-immobilize IO3−.•(IO3−)-incorporated ettringite carbonation within cement pore spaces may help retain IO3−.</description><subject>Dissolution</subject><subject>Incorporation/retention by secondary mineral formation</subject><subject>Mobilization</subject><subject>Oxyanion substitution</subject><subject>Radionuclide</subject><issn>0883-2927</issn><issn>1872-9134</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2021</creationdate><recordtype>article</recordtype><recordid>eNqFUE1PAyEQJUYTa_U3uPG-FVgE9lgbv5ImXvRMWBi6NG2pwDbx38tmjVdPM_My782bh9AtwQuCCb_fLvRxA8H0sF9QTEeUSd6coRmRgtYtadg5mmEpm5q2VFyiq5S2GOMHgekMLR-h1ycfYhVc5YPVGao0dCn7PGSwFeQc_WHjC2yHsav01wBhSNUOtOkLcI0unN4luPmtc_T5_PSxeq3X7y9vq-W61oywXDtrGyM560gZuXWEGUla0zkjoWPUQou1FBK4YAI3rWuYk1a0nBfTBoRs5uhu0g3FnEqmWDK9CYcDmKyIxC1ntCyJacnEkFIEp47R73X8VgSrMS61VX9xqTEuNcVVmMuJCeWHk4c4noCDAevjeMEG_6_GDykxd_Q</recordid><startdate>202102</startdate><enddate>202102</enddate><creator>Avalos, Nancy M.</creator><creator>Varga, Tamas</creator><creator>Mergelsberg, Sebastian T.</creator><creator>Silverstein, Joshua A.</creator><creator>Saslow, Sarah A.</creator><general>Elsevier Ltd</general><general>Elsevier</general><scope>AAYXX</scope><scope>CITATION</scope><scope>OTOTI</scope><orcidid>https://orcid.org/0000-0002-5492-866X</orcidid><orcidid>https://orcid.org/0000-0002-8385-2676</orcidid><orcidid>https://orcid.org/0000-0001-8073-4642</orcidid><orcidid>https://orcid.org/0000000180734642</orcidid><orcidid>https://orcid.org/000000025492866X</orcidid><orcidid>https://orcid.org/0000000283852676</orcidid></search><sort><creationdate>202102</creationdate><title>Behavior of iodate substituted ettringite during aqueous leaching</title><author>Avalos, Nancy M. ; Varga, Tamas ; Mergelsberg, Sebastian T. ; Silverstein, Joshua A. ; Saslow, Sarah A.</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-a414t-fdd3c864b14146df14c819cbfc8eb42de90a878e6747039f34f8d7966292ce783</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>2021</creationdate><topic>Dissolution</topic><topic>Incorporation/retention by secondary mineral formation</topic><topic>Mobilization</topic><topic>Oxyanion substitution</topic><topic>Radionuclide</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Avalos, Nancy M.</creatorcontrib><creatorcontrib>Varga, Tamas</creatorcontrib><creatorcontrib>Mergelsberg, Sebastian T.</creatorcontrib><creatorcontrib>Silverstein, Joshua A.</creatorcontrib><creatorcontrib>Saslow, Sarah A.</creatorcontrib><collection>CrossRef</collection><collection>OSTI.GOV</collection><jtitle>Applied geochemistry</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Avalos, Nancy M.</au><au>Varga, Tamas</au><au>Mergelsberg, Sebastian T.</au><au>Silverstein, Joshua A.</au><au>Saslow, Sarah A.</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Behavior of iodate substituted ettringite during aqueous leaching</atitle><jtitle>Applied geochemistry</jtitle><date>2021-02</date><risdate>2021</risdate><volume>125</volume><issue>C</issue><spage>104863</spage><pages>104863-</pages><artnum>104863</artnum><issn>0883-2927</issn><eissn>1872-9134</eissn><abstract>Ettringite [Ca6Al2(SO4)3(OH)12·26H2O] found in cementitious waste forms (CWFs) is known to immobilize iodate (IO3−) via sulfate (SO42-) substitution; however, limited studies have investigated the effects of leaching on the long-term fate and behavior of IO3− retained in ettringites. In this study, ettringite mineral transformation and iodine release from IO3−-incorporated ettringite ((IO3−)-Ett) were investigated using batch experiments to determine the mechanisms likely to drive IO3− release/retention within ettringite in environmentally relevant solutions of varying composition, pH, and alkalinity. (IO3−)-Ett was leached in six simulated solutions relevant to the Hanford Site (Washington State, USA) for a period of 56 days: double deionized water, 24 ppm CO32-, 1400 ppm SO42-, Hanford groundwater, Hanford vadose zone porewater and a cement-equilibrated solution. By monitoring IO3− uptake and removal and characterizing changes in the solid material, incongruent dissolution of ettringite to calcite and oxyanion substitution into the ettringite structure (e.g., SO42- or CO32-) were identified as contributing IO3− release mechanisms. However, the formation of calcium carbonates, e.g., calcite, may re-incorporate IO3− (pH < 10) or prevent the release of IO3− when formed on solution-exposed surfaces of ettringite. These results provide valuable insights into iodine release from CWFs that may be used to improve current CWF formulations for the treatment of iodine-containing nuclear waste.
[Display omitted]
•CO32- and SO42- ions mineralogically transform (IO3−)-incorporated ettringite and cause the release of retained IO3−.•(IO3−)-incorporated ettringites formed at the surface of cement will be susceptible to transformation and IO3− release.•The formation of calcite at pH < 10 may re-immobilize IO3−.•(IO3−)-incorporated ettringite carbonation within cement pore spaces may help retain IO3−.</abstract><cop>United Kingdom</cop><pub>Elsevier Ltd</pub><doi>10.1016/j.apgeochem.2020.104863</doi><orcidid>https://orcid.org/0000-0002-5492-866X</orcidid><orcidid>https://orcid.org/0000-0002-8385-2676</orcidid><orcidid>https://orcid.org/0000-0001-8073-4642</orcidid><orcidid>https://orcid.org/0000000180734642</orcidid><orcidid>https://orcid.org/000000025492866X</orcidid><orcidid>https://orcid.org/0000000283852676</orcidid><oa>free_for_read</oa></addata></record> |
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| subjects | Dissolution Incorporation/retention by secondary mineral formation Mobilization Oxyanion substitution Radionuclide |
| title | Behavior of iodate substituted ettringite during aqueous leaching |
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