Chloride and heavy metal binding capacities of hydrotalcite-like phases formed in greener one-part sodium carbonate-activated slag cements

The treatment of industrial solid wastes requires a proper binder that can efficiently solidify and stabilize the harmful containments. Previous studies have shown that the incorporation of calcined dolomite (CD) in the one-part sodium carbonate-activated blast furnace slag binder promotes the formation of hydrotalcite-like phases, which exhibit a potentially high ion-binding capacity. This study investigates the chloride and heavy metals binding capacities of the hydrotalcite-like phases formed in the binder. The results show that this binder has higher resistance to chloride penetration than the Portland cement and other alkali-activated slag pastes. The solidification efficiencies of Pb2+, Cu2+ and Cr3+ ions for the binder with 10% CD dosage are in the range of 66-88%. The hydrotalcite formation mechanism proposed in this work suggests that the carbonate ion-exchange in the interlayer of hydrotalcite reduces the available binding sites, so the binding capacity is mainly attributed to the physical surface adsorption, rather than interlayer ion-exchange. The CO2 emission and energy consumption of this binder are around 80% lower than the PC paste. This study provides a guidance for the production of greener binder for the use in the treatment of industrial solid wastes. (C) 2020 Elsevier Ltd. All rights reserved.