title: Chabazite: stable cation-exchanger in hyper alkaline concrete pore water.
abstract: To avoid impact on the environment, facilities for permanent disposal of hazardous waste adopt multibarrier design schemes. As the primary barrier very often consists of cement-based materials, two distinct aspects are essential for the selection of suitable complementary barriers: (1) selective sorption of the contaminants in the repository and (2) long-term chemical stability in hyperalkaline concrete-derived media. A multidisciplinary approach combining experimental strategies from environmental chemistry and materials science is therefore essential to provide a reliable assessment of potential candidate materials. Chabazite is typically synthesized in 1 M KOH solutions but also crystallizes in simulated young cement pore water, a pH 13 aqueous solution mainly containing K(+) and Na(+) cations. Its formation and stability in this medium was evaluated as a function of temperature (60 and 85 °C) over a timeframe of more than 2 years and was also asessed from a mechanistic point of view. Chabazite demonstrates excellent cation-exchange properties in simulated young cement pore water. Comparison of its Cs(+) cation exchange properties at pH 8 and pH 13 unexpectedly demonstrated an increase of the KD with increasing pH. The combined results identify chabazite as a valid candidate for inclusion in engineered barriers for concrete-based waste disposal.
authors.affiliation: Centre for Surface Chemistry and Catalysis, KU Leuven , Kasteelpark Arenberg 23 - box 2461, 3001 Heverlee, Belgium.
authors.forename: Leen
authors.initials: L
authors.lastname: Van Tendeloo
authors.forename: Wauter
authors.initials: W
authors.lastname: Wangermez
authors.forename: Mert
authors.initials: M
authors.lastname: Kurttepeli
authors.forename: Benny
authors.initials: B
authors.lastname: de Blochouse
authors.forename: Sara
authors.initials: S
authors.lastname: Bals
authors.forename: Gustaaf
authors.initials: G
authors.lastname: Van Tendeloo
authors.forename: Johan A
authors.initials: JA
authors.lastname: Martens
authors.forename: André
authors.initials: A
authors.lastname: Maes
authors.forename: Christine E A
authors.initials: CE
authors.lastname: Kirschhock
authors.forename: Eric
authors.initials: E
authors.lastname: Breynaert
mesh_terms: D002414:Cations, Monovalent / Q000737:chemistry; D002586:Cesium / Q000737:chemistry*; D006256:Hazardous Waste; D006863:Hydrogen-Ion Concentration; D008855:Microscopy, Electron, Scanning; D011188:Potassium / Q000737:chemistry*; D012037:Refuse Disposal / Q000379:methods; D012964:Sodium / Q000737:chemistry*; D012996:Solutions; D013696:Temperature; D014867:Water / Q000737:chemistry; D017641:Zeolites / Q000737:chemistry*
chemical_list: D002414:Cations, Monovalent; D006256:Hazardous Waste; D012996:Solutions; C554923:chabazite; D014867:Water; D017641:Zeolites; D002586:Cesium; D012964:Sodium; D011188:Potassium