Blast furnace slags as sorbents of phosphate from water solutions

The paper is focused on the sorption of phosphorus from aqueous solutions by crystalline and amorphous blast furnace slags. Slag sorption kinetics were measured, adsorption tests were carried out and the effect of acidification on the sorption properties of slags was studied. The kinetic measurements confirmed that the sorption of phosphorus on crystalline as well as amorphous slags can be described by a model involving pseudo-second-order reactions. For all slag types, phosphorus sorption follows the Langmuir adsorption isotherm. The acid neutralizing capacities of crystalline and amorphous slags were determined. In the case of the crystalline slags, buffering intervals were found to exist during which the slag minerals dissolve in the sequence bredigite-gehlenite-diaspor. There is a high correlation (R2=0.9989) between ANC3.8 and the saturation capacities of crystalline and amorphous slags.