Adsorption Study of Pb(II) Ions on the Blast Furnace Slag (BFS) from Aqueous Solution

In this work, blast furnace slag (BFS) was used as an adsorbent material for the removal of Pb (II) ions in solution in batch mode. The physico-chemical analysis used indicated that the BFS is essentially composed of silica, lime, and alumina. Its specific surface area was 275.8 m²/g and its PZC was around 3.8. The adsorption study indicated that the maximum amount of Pb (II) adsorbed under optimum conditions (agitation speed (Vag): 150 rpm; pH: 5.4; particle size (Øs): 300µm, T: 20°C) was 34.26 mg/g after 50 minutes of agitation, and adsorption yield was best for feeble initial concentrations. The most appropriate isothermal model was that of Langmuir, and the adsorption speed was better characterized by the pseudo-second order kinetic model. The adsorption mechanism study revealed that internal diffusion is not the only mechanism that controls the adsorption process and there is also an external diffusion, which contributes enormously in the transfer of Pb (II) from solution to adsorbent. Thermodynamic study indicated that the Pb (II) adsorption on the blast furnace slag (BFS) was spontaneous, exothermic, and that the adsorbed Pb (II) is more ordered at the surface of the adsorbent.