Abstract
Slags, sludges, and dust from steelmaking industries have been probed as adsorbents for Pb(II) removal from synthetic water solutions, and these residues have showed good potential in the treatment of industrial effluents contaminated with this heavy metal. Adsorption and precipitation of Pb(II) have been postulated as the main mechanisms to remove Pb(II) from aqueous solutions by using steelmaking residues. The significant effect of pH on Pb(II) removal has been well studied but few studies explicitly address the effect of chemical and mineralogical composition of steelmaking residues and a better understanding of this key parameter is still needed for full elucidation and optimization of the Pb(II) removal process. In this study, samples obtained from different sections of a dust collector system (BFD) in a steelmaking factory, were used to evaluate the effect of BFD sample’s chemical composition on the removal of Pb(II) from synthetic aqueous solution. BFD samples were characterized to determine their chemical composition, particle size distribution and isoionic point. Equilibrium and transient experiments of Pb(II) removal from aqueous solutions were conducted a 25 °C and initial pH = 5.0. Results showed that CaO and MgO, as well as metallic Fe and FeO had a positive linear effect BDF samples Pb(II) adsorption capacity. Pb(II) removal process may take place by ion exchange with CaO and MgO, and by precipitation on the surface of metallic Fe and FeO. MgO and FeO promoted the Pb(II) removal in lesser extend that CaO and metallic Fe, respectively, because the surface ion exchange with MgO and FeO are less thermodynamic favourable and their lower composition in the sample. Bimolecular ion exchange process between Pb(II) ions and Ca and Fe species was supported by results from equilibrium and transient adsorption studies. Results of this work clearly showed that removal of Pb(II) from aqueous solutions is a strong function of the chemical composition of BFD samples and it provided further insight to promote the valorisation and optimization of steelmaking residues as heavy-metal adsorbents.
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