Sorption characteristics of fluoride on to magnesium oxide-rich phases calcined at different temperatures

The effect of calcination temperature during production of magnesium oxide-rich phases from MgCO3 on the sorption of F- ions in the aqueous phase has been investigated. Magnesium oxide-rich phases were formed by calcination at over 873 K for 1 h. Higher calcination temperatures produced more crystalline MgO with smaller specific surface area and provided larger values of the total basicity per unit surface area. The higher calcination temperatures lead to slower F- removal rate, and lower equilibrium F- concentrations, when the equilibrium F- concentrations are less than 1 mmol dm(-3). Larger total basicity per unit surface area made the reactivity with F- ions in aqueous phase more feasible, resulting in a greater degree of F- sorption. For equilibrium F- concentrations more than 1 mmol dm(-3), lower calcination temperatures favored the co-precipitation of F- with Mg(OH)(2), probably leading to the formation of Mg(OH)(2-x)F-x, and the achievement of larger sorption density. This is the first paper which describes the relationship between the solid base characteristics obtained by CO2-TPD for MgO with different calcination temperatures as a function of the reactivity of F- sorption in the aqueous phase. (C) 2011 Elsevier B.V. All rights reserved.