Surface modification and dissolution behavior of Mg–Al hydrotalcite particles

The dissolution behavior of Mg–Al–CO32– hydrotalcite (AHT) in aqueous solution was studied. The AHT dissolution strongly depended on pH and temperature, and the dissolution of AHT fitted the surface chemical reaction model well. The apparent activation energy during the dissolution process was 34.11 kJ/mol, which further confirmed that the dissolution was controlled by the surface chemical reaction. During the SO42– modification, the exchange process between SO42– and CO32– in interlayer spaces of the AHT took place along with Mg2+ partial dissolution from edges of the brucite sheets. On the other hand, the modification mechanism of the AHT was discussed based on the dissolution–reprecipitation (D–R) mechanism. The modification process was suggested to occur on the solid/water interface, i.e., dissolution of Al-ions and Mg2+, adsorption and reprecipitation of the Al aqua ions on the surface of the solids.