Towards sustainable battery recycling: selective dynamic adsorption of nickel(II) and cobalt(II) in an adsorbent fixed-bed reactor at elevated temperature

Caused by the scarce resources of critical heavy metals which are in high demand, e.g., for lithium-ion batteries, processes for the recovery of such materials for recycling are of high interest. Adsorption is an effective method in order to selectively separate metal ions from aqueous solutions. Unfortunately, the prerequisites in battery recycling, like acidic pH-value and high temperature, are in general impairing the adsorption process. In this study, the competitive dynamic adsorption of nickel(II) (Ni(II)) and cobalt(II) (Co(II)) by a silica adsorbent functionalized with amino-polycarboxylate derivative ligands (designated as HSU331) under recycling process conditions, (pH = 3.5, T = 20 °C, and T = 50 °C, respectively) and varying concentrations (Ni(II):Co(II) 1:1 (5.0, and 10 mmol·L⁻¹, respectively), Ni(II):Co(II) 3:1 and 1:3 (3.0 mmol·L⁻¹ and 1.0 mmol·L⁻¹ vice versa)) were investigated. A displacement desorption of Co(II) in favor of the binding of Ni(II) was observed, achieving maximum loadings of 0.95 µmol_Ni(II)·µmol_Ligand⁻¹ (28.3 mg_Ni(II)·g_Adsorbent⁻¹), and 0.48 µmol_Co(II)·µmol_Ligand⁻¹ (14.3 mg_Co(II)·g_Adsorbent⁻¹) at T = 20 °C and 1.0 µmol_Ni(II)·µmol_Ligand⁻¹ (29.9 mg_Ni(II)·g_Adsorbent⁻¹) and 0.18 µmol_Co(II)·µmol_Ligand⁻¹ (5.38 mg_Co(II)·g_Adsorbent⁻¹) at T = 50 °C, respectively. These results demonstrate a distinctly selective separation of Ni(II) in the presence of Co(II) by HSU331, achieving an even higher efficiency at elevated temperatures.