PMID: 16646464May 2, 2006Paper

Spectroscopic investigation of Ni speciation in hardened cement paste

Environmental Science & Technology
M VespaA M Scheidegger

Abstract

Cement-based materials play an important role in multi-barrier concepts developed worldwide for the safe disposal of hazardous and radioactive wastes. Cement is used to condition and stabilize the waste materials and to construct the engineered barrier systems (container, backfill, and liner materials) of repositories for radioactive waste. In this study, Ni uptake by hardened cement paste has been investigated with the aim of improving our understanding of the immobilization process of heavy metals in cement on the molecular level. X-ray absorption spectroscopy (XAS) coupled with diffuse reflectance spectroscopy (DRS) techniques were used to determine the local environment of Ni in cement systems. The Ni-doped samples were prepared at two different water/cement ratios (0.4, 1.3) and different hydration times (1 hour to 1 year) using a sulfate-resisting Portland cement. The metal loadings and the metal salts added to the system were varied (50 up to 5000 mg/kg; NO3(-), SO4(2-), Cl-). The XAS study showed that for all investigated systems Ni(ll) is predominantly immobilized in a layered double hydroxide (LDH) phase, which was corroborated by DRS measurements. Only a minor extent of Ni(ll) precipitates as Ni-hydroxides (alpha-Ni(...Continue Reading

References

Aug 16, 2000·Journal of Colloid and Interface Science·K G Scheckel, D L Sparks
Aug 22, 2001·Journal of Synchrotron Radiation·A M ScheideggerP Spieler
May 12, 2006·Journal of Synchrotron Radiation·T Ressler

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Citations

Jul 23, 2013·Acta Crystallographica Section B, Structural Science, Crystal Engineering and Materials·Ian G Richardson
Sep 20, 2016·Journal of Hazardous Materials·Amitava Roy, Julia A Stegemann
Nov 26, 2009·Environmental Science & Technology·Edward PeltierDonald L Sparks
Nov 21, 2009·Environmental Science & Technology·Peter MandalievErich Wieland

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