Investigation of selective and effective recovery of noble metal osmium by adsorption onto nano-Al2O3 particles

Abstract

A simple method for the rapid separation and recovery of osmium (Os(IV)) was developed. It was found that Os(IV) ions could be adsorbed quantitatively (above 99%) in the pH range 3.0–7.0, suggesting that γ-nano-Al₂O₃ was an excellent adsorbent for Os(IV) ions. The adsorbed Os(IV) ions could then be rapidly eluted with 0.1 mol L⁻¹ HCl. The Os(IV) adsorption reaction was found to be fast, and equilibrium was attained within 5.0 min following a pseudo-second-order model with an observed rate constant (k₂) of 0.16 g mg⁻¹ min⁻¹ (298 K). The adsorption data could be interpreted by the Langmuir model with a maximum adsorption capacity of 21.71 mg g⁻¹ (298 K). Moreover, the thermodynamic parameters showed the endothermic and spontaneous nature of the adsorption process. Investigation of the adsorption selectivity showed that γ-nano-Al₂O₃ displayed strong affinity for osmium and exhibited good selectivity for osmium in the presence of Cu(II), Ni(II), Cd(II), Zn(II), Co(II), Fe(III) and Pb(II).