Inmobilization of Zn(II) in Portland cement pastes. Determination of microstructure and leaching performance

The aim of this paper is to study the solidification/ stabilization potential of cementitious matrices on the immobilization of Zn(II) before its disposal into the environment by determining the mechanisms of interaction between the Zn(II) ions and the binder. The results of structural and mineralogical characterization of cement pastes formed with different amounts of immobilized Zn(II) ions are presented and the study includes results from thermogravimetric analysis (TG), scanning electron microscopy, X-ray diffraction, and leaching performance. Zn(II) ions delay the hydration reaction of Portland cement due to the formation of mainly CaZn2(OH)6 2H2O , as well as Zn5(CO3)2(OH)6, Zn(OH)2, and ZnCO3 in minor proportion. Correlations between total mass loss in TG analysis and leached Zn(II) ions in long-term curing pastes have been obtained. This result is important because in a preliminary approach from a TG on an early-aged cement paste containing Zn(II), it could be possible to perform an estimation of the amount of Zn(II) ions that could be leached, thus avoiding costly and time-consuming tests.Mellado Romero, AM.; Borrachero Rosado, MV.; Soriano Martinez, L.; Paya Bernabeu, JJ.; Monzó Balbuena, JM. (2013). Inmobilization of Zn(II) in Portland cement pastes. Determination of microstructure and leaching performance. Journal of Thermal Analysis and Calorimetry. 112(3):1377-1389. doi:10.1007/s10973-012-2705-8S13771389112