An X-ray diffraction (XRD) and Fourier transform infrared spectroscopic (FT-IR) investigation of the long-term effect on the solidification/stabilization (S/S) of arsenic(V) in Portland cement type-V

Autor: Mollah, Mohammad Y.A.1 myamollah@hotmail.com, Kesmez, Mehmet2, Cocke, David L.2 cockedl@hal.lamar.edu
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Zdroj: Science of the Total Environment. Jun2004, Vol. 325 Issue 1-3, p255-262. 8p.
Abstrakt: The long-term effects on solidification/stabilization (S/S) of As5+-bearing oxyanions (AsO3-4) in Portland cement type-V (OPC) have been investigated by X-ray diffraction (XRD) and Fourier transform infrared spectroscopic (FT-IR) techniques. The results of this study confirm our previous results that the early hydration of cement is inhibited by the presence of AsO3-4, and that the inhibition is mainly caused by the formation of highly insoluble Ca3(AsO4)2 on the surface of hydrating cement particles. Arsenate analog of ettringite [Ca6(Al2O6)(SO4)3·32H2O] was identified in the early stages of hydration of pure Portland cement and As(V)-treated Portland cement [OPC-As(V)], but not in 10-year-old similar samples. The XRD and FT-IR results indicated interactions of oxyanions and cement particles to produce minor quantities of As5+-bearing compounds in fresh as well as in 10-year-old samples. New As5+-bearing phases, NaCaAsO4·7.5H2O and Ca5(AsO4)3OH were identified in the 10-year-old OPC-As(V) samples by XRD analyses. Based on these results it is concluded that Portland cement may be considered as a potential matrix to immobilize As5+-bearing wastes. [Copyright &y& Elsevier]
Databáze: GreenFILE
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