Nano-hematite bagasse composite (n-HBC) for the removal of Pb(II) from dilute aqueous solutions

Abstract

Nano-hematite bagasse composite (n-HBC) was synthesized, characterized and tested for the removal of Pb(II) from dilute aqueous solutions. The particle size of ferric oxide was in the range of 100–300nm. The composite surface, both internal and external, was occupied by abundant oxygen-containing functional groups. The optimum Pb(II) adsorption density occurred in the pH range from 4.0 to 5.5. Adsorption reached equilibrium rapidly in 480, 600, 720min at initial Pb(II) concentration of 20, 30, and 40mg/L, respectively, at 25°C and pH 5.0. The maximum Pb(II) adsorption capacity, calculated from the Langmuir adsorption isotherm, was 16.57mg/g at 25°C. Furthermore, surface complexation model was also applied to describe the adsorption reaction between aqueous Pb(II) and n-HBC. The Gibbs free energy of adsorption, ΔGads0, was −39.49kJ/mol (9.44kcal/mol) at 25°C, which indicated spontaneous Pb(II) ion adsorption on n-HBC. Results of XPS studies demonstrated the presence of surface oxygen-containing functional groups, which were involved in the adsorption of Pb(II) and that hematite played a key role in Pb (II) uptake.