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  1. Abstract

    Synthetic hydrotalcites were produced by a co‐precipitation method. The hydrotalcites are represented by the general formula [MII(1‐x)MIII(x)(OH)2][An−]x/n·zH2O, where MIIis a divalent cation (eg, Mg2+or Ca2+), MIIIis a trivalent cation (eg, Al3+) and An−is the interlayer anion. Herein, MII = Mg, and MIII = Al such that [Mg/Al] = [2, 3] (atomic units) and An−, represents intercalant species including: OH, SO42−and CO32−anions. The thermochemical data of each compound including their solubility constants (Kso), density and molar volume were quantified at T = 25 ± 0.5°C, andP = 1 bar. The solubilities of the synthetic hydrotalcites, irrespective of their divalent‐trivalent cation partitioning ratio, scaled as CO32− < SO42− < OH; in order of decreasing solubility. The type of anion, very slightly, affected the solubility with less than ±1 log unit of variation for [Mg/Al] = 2, and ±2 log units of variation for [Mg/Al] = 3. The solubilities of these phases were strongly correlated with that of gibbsite (Al(OH)3); such that activity of the [AlO2] species wassolubility determiningwith increasing pH. The tabulated thermodynamic data were used to construct solid‐solution models for phases encompassing both cation distribution ratios and to calculate stable phase equilibria relevant to alkali‐activated slag (AAS) systems for diverse activator compositions.

     
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