Cement-based stabilization/solidification (S/S) is a cost-efficient technology for sustainable waste management. Among various types of cements, magnesium-rich cement (Mg-cement) is one of the most promising materials for sustainable S/S. Its high Mg content promotes the formation of hydrotalcite, which belongs to the family of layered double hydroxide (LDH) with an outstanding scavenger for toxic anions via anion exchange. Moreover, iron, originating from either supplementary cementitious materials (SCMs) or hazardous wastes, can be structurally incorporated into the Mg-Al main octahedral layer of hydrotalcite, forming various FeII/Mg-FeIII/Al hydrotalcites (abbr. Fe-hydrotalcites). The Fe sites could largely affect the thermodynamic stability and contribute to their sorption capacity. Although Fe-hydrotalcites can act as very promising binders for redox-sensitive toxic oxyanions (e.g., AsO43– and CrO42−) and play critical roles in S/S process, fundamental atomic-scale understanding on the redox behaviors of FeII/III sites under alkaline conditions is still lacking. This project will apply cutting-edge experimental characterizations and advanced theoretical simulations on an atomic scale to elucidate the thermodynamic models for Fe-hydrotalcite solid solutions, the transformation pathways between FeII and FeIII sites, and the immobilization mechanisms of the redox-sensitive anions. A large impact in both academic and industry fields can be achieved with respect to the development of both S/S technology and low-carbon Mg-rich cement.

Contact:

Dengquan Wang, Jiaxing Ban, Maciej Delekta, Barbara Lothenbach, John Provis, Sergey Churakov, Bin Ma

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