Sorption of Rare Earth Elements onto Iron oxides – Nil Cedacers Pla

Abstract:

The adsorption experiments of rare-earth elements (REEs) onto Ferrihydrite and Goethite were performed to understand the behaviour of the REEs when they enter in contact with the Fe oxides in different environments. Batch experiments were performed at pH 3 , 4, 5, 6, 7 to see the interaction between the REEs with this Fe oxides. The solutions were prepared with 20mg of Fe oxide and a 50μg/L REEs concentration. The solutions were exposed in to different pH conditions and after 36h of pH control were filtrated in order to obtain the solution without Fe oxides and particles. The solutions were analysed with the Inductively Coupled Plasma Mass Spectrometer (ICP MS) to know the concentration of the REEs that weren’t absorbed into the Fe oxides. The results revealed that at high pH (pH 7) barely all the REEs were absorbed while at low pH (pH 3) they weren’t. At acid environments sorption sites are protonated but if we increase the pH, the sorption sites are deprotonated and disponible for REEs in solution. Cerium anomalies were found in the Ferrihydrite (Fh) due to his oxidation from Ce (III) to Ce (IV) giving one electron to the Fe (III) and reducing it at Fe (II). Also we found some anomalies with europium (Eu) in the Goethite results. The results revealed too that in pH 4,5,6 the Light REEs were easily more absorbed than the Heavy REEs. Finally, due the situation, we couldn’t use the Ultraviolet-visible spectroscopy to find the Fe (II) / Fe (III) ratio in the final solution. …víceméně