Alkali-Activation of Blast Furnace Slag as Possible Modification for Improving Sorption Properties of Heavy Metals

New direction of research uses the alkali-activated slags as sorbents for removing metals cations from the solution. Slag materials mo - dified by alkali-activation were prepared by interaction of blast furnace slag (BFS Basic) with water glass. The prepared alkali-activa - ted slags were dried under different conditions to form new structure in slag. The slag dried at room temperature for 7 days (AA BFS) and in a dryer at 105°C for 8 hours (AA BFS 105) were prepared and characterized with the aim to study their sorption properties. Characterization of the prepared slags by means of infrared spectrometry (with diffuse reflectance method) demonstrates that the alkaline activation forms a new structure. The new structures are products of hydration processes and structural changes after contact with water glass. Changes are significant in the comparison with original blast furnace slag. The influence of this new structure on the sorption properties was studied for the copper Cu(II) and lead Pb(II) cations. The sorption experiments were performed by batch method in the aqueous solutions without pH treatment for the concentration range 2–140 mmol/L. The maximum removal amounts of Cu(II) on the alkali-activated slags were almost three times higher and the maximum removal amounts of Pb(II) were at least twice higher in comparison to the BFS Basic. Removal efficiency achieved almost 100% to initial concentration 20 mmol/L for Cu(II) and Pb(II). The removal efficiency for both cations decreases with increasing concentration of metals cations. The removal efficiency is higher for both alkali-activated blast furnace slags in the comparison with BFS Basic. A mechanism of the metal cations removing is influenced by self-alkalization and the removing is mainly due to precipitation and complexation of copper and lead cations on the surface of slags. The alkaline activated slags can be possibly used for remediation of wastewater containing metals ions.