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Zeolite P in cements: Its potential for immobilizing toxic and radioactive waste species
Zeolite P, approximately (Na2O, CaO).(Al2O3).(2SiO2).(4H2O), has been shown to develop spontaneously in appropriate cement formulations at > 40 deg C, and to be a stable phase. Suitable composites can be made from mixtures containing Ca(OH)2 or Portland cement, with high proportions of the pozzolans, metakaolin or class F fly ash. Alternatively, zeolite P is easily prepared in phase-pure form using laboratory chemicals. The latter method was used to obtain zeolite P of composition (0.9CaO).(0.1Na2O).(Al2O3).(2.66SiO2).(4H2O), on which characterization studies were performed for its sorption potential in cement-analogue environments. Values of the distribution ratio RD are reported for the 25 deg C and 85 deg C isotherms, for a range of initial sorbate concentrations (10 micromol/l to 10000 micromol/l). The sorbates investigated were: Cs, Sr, Ba, Pb and U(VI). In water media, zeolite P shows good selectivity for Cs, Sr, Ba and Pb, at 25 deg C and 85 deg C. The highest RD recorded was for Pb(2+), at > 800000 ml/g (1000 micromol/l initial concentration). In NaOH media, Ba and Sr sorption values remained high. Cs and Pb show a marked decrease in sorption, also values of RD are still reasonable, at about 750 ml/g and about 400 ml/g, respectively. On account of its large ion size, UO2(2+) uptake into zeolite P is negligible, remaining in solution or precipitating as soddyite or Na uranate. Cements conditioned to form stable zeolites offer great potential in the treatment of hazardous waste streams.
Zeolite P in cements: Its potential for immobilizing toxic and radioactive waste species
Zeolite P, approximately (Na2O, CaO).(Al2O3).(2SiO2).(4H2O), has been shown to develop spontaneously in appropriate cement formulations at > 40 deg C, and to be a stable phase. Suitable composites can be made from mixtures containing Ca(OH)2 or Portland cement, with high proportions of the pozzolans, metakaolin or class F fly ash. Alternatively, zeolite P is easily prepared in phase-pure form using laboratory chemicals. The latter method was used to obtain zeolite P of composition (0.9CaO).(0.1Na2O).(Al2O3).(2.66SiO2).(4H2O), on which characterization studies were performed for its sorption potential in cement-analogue environments. Values of the distribution ratio RD are reported for the 25 deg C and 85 deg C isotherms, for a range of initial sorbate concentrations (10 micromol/l to 10000 micromol/l). The sorbates investigated were: Cs, Sr, Ba, Pb and U(VI). In water media, zeolite P shows good selectivity for Cs, Sr, Ba and Pb, at 25 deg C and 85 deg C. The highest RD recorded was for Pb(2+), at > 800000 ml/g (1000 micromol/l initial concentration). In NaOH media, Ba and Sr sorption values remained high. Cs and Pb show a marked decrease in sorption, also values of RD are still reasonable, at about 750 ml/g and about 400 ml/g, respectively. On account of its large ion size, UO2(2+) uptake into zeolite P is negligible, remaining in solution or precipitating as soddyite or Na uranate. Cements conditioned to form stable zeolites offer great potential in the treatment of hazardous waste streams.
Zeolite P in cements: Its potential for immobilizing toxic and radioactive waste species
Die Untersuchung von Möglichkeiten zur Immobilisierung von toxischen und radioaktiven Abprodukten durch eine Adsorption an Zeolith P in zementhaltigen Materialien
Atkins, M. (author) / Glasser, F.P. (author) / Jack, J.J. (author)
Waste Management ; 15 ; 127-135
1995
9 Seiten, 8 Bilder, 6 Tabellen, 23 Quellen
Article (Journal)
English
Abfall (Müll) , gefährlicher Stoff , Abfall (Kerntechnik) , Zeolith , Ionenaustausch , Adsorbieren , Isotherme , Portlandzement , Flugasche , Zustandsdiagramm , ternäres System , Röntgenstrukturanalyse , Elektronenmikroskop , thermische Eigenschaft , Temperaturabhängigkeit , pH-Wert , Atomabsorptionsspektrometrie , Flammenspektroskopie , Massenspektrometrie , Adsorptionsisotherme
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