Neodymium recovery from aqueous solution through adsorption/desorption onto expanded vermiculite

The noble application of the neodymium on the technological field provides its high aggregate value. However, the future supply depends on the recycle, which still needs the improvement of the classical separation methods. In this study, expanded vermiculite was employed as an adsorbent to neodymium recovery from aqueous solution in batch mode. The specific properties of this phyllosilicate such as the lamellar structure were confirmed by different analytical techniques. The equilibrium of adsorption was well explained by Langmuir achieving the maximum adsorption capacity of 0.48 mmol/g at 283 K. The process was exothermic, spontaneous, and classified as physical adsorption. Desorption experimental conditions were optimized using the response surface methodology. The calcium chloride (0.3 mol/L) as eluent guaranteed a high recovery of neodymium and great reusability to the adsorbent material, achieving an uptake efficiency of 94% and a neodymium recovery of 95% in the fifth cycle. Thus, this commercial clay mineral demonstrated a great potential to recover neodymium from aqueous solution, due to the high adsorption and desorption efficiency after successive cycles of reuse.