Modification mechanism of Mg-Al hydrotalcites and adsorption performance

The modified Mg-Al hydrotalcite was prepared by using (NH4)2SO4 and characterized by XRD, FT-IR, SEM and EDS. The aqueous solubility and modified mechanism of Mg-Al hydrotalcite have been investigated. The results show that the solubility of Mg-Al hydrotalcite can be divided mainly into three dissolution behaviors: no solubility, partical and complete solubility. The modification of Mg-Al hydrotalcite is the partical dissolution process. In the corrosion of the Mg-Al hydrotalcite, Mg ions were dissoved from the brucite-like sheets and led Al ions into the reaction solution. Aquated ions Al(OH)63- in the solution aggregated to form Keggin structure Al13 cluster. The Al13 cluster was adsorbed rapidly on the surface of the sheets, and then formed amorphous Al(OH)3 which prevented the further solution of Mg ions from the sheet. The absorption performation on Pb2+ was improved, and Pb2+ removal rate of the modified products is raised by 18.3%. The improved adsoption property is mainly due to the increase of specific surface erea, chemical bonding and electrostatic adsorption ability. © right.