Removal of lead(II) from aqueous solutions by blast-furnace metallurgical slags

The possibility for Pb(II) removal from aqueous solutions by ungranulated and granulated blast-furnace slags from the ferrous metallurgy is studied. The sorpion capacities for Pb(II) of both slags (size 0.25-0.50 mm) in solutions with initial metal ion concentration of 50 mg/L are compared. The effect of contact time (5-240 min), the dose of slags (0.25-15 g/L) and pH (3-10) are studied. The data obtained from the kinetic experiments show that the process of Pb(LI) removal by metallurgical slags is mainly controlled by the internal diffusion. The values of rate constants and internal diffusion constants are determined. The maximum capacities of these two materials are determined from the sorption isotherms, obtained for various doses of the slags. When the pH is 5, these maximum capacities are respectively 75 mg/g for ungranulated slag and 71 mg/L for granulated slag. The efficiency of Pb(II) removal from the solution increases with the rise of pH and for both materials the maximum removal (95-97 %) is observed at pH 5.9-6.0. The comparative study for the sorption capacity of the blast-furnace slags shows that the ungranulated slag is almost two times more effective than granulated slag.