Processes developed for the separation of europium (Eu) from various resources

Recovery of europium from E-waste using redox active tetrathiotungstate ligands

Rare-earth elements (REEs) are critical to our modern economy, yet their mining from natural ores bears a profound environmental impact. Traditional separation techniques are chemical and energy-intensive because their chemical similarities make REEs very challenging to purify, requiring multiple extraction steps to achieve high purity products. This emphasizes the need for sustainable and straightforward separation methods. Here we introduce a strategy for the direct separation of europium (Eu) from complex mixtures under ambient conditions, leveraging on the redox non innocence of purely inorganic tungsten tetrathiolate (WS42-) ligands. The recovery of Eu is achieved upon reduction of Eu(III) to a Eu(II) coordination polymer, driven by an induced internal electron transfer from the tetrathiotungstate ligand. Applying this strategy to unconventional feedstock such as spent energy-saving lamps allows selective europium recovery with separation factors over 1000 and recovery efficiency as high as 99% without pre-treatment of the waste.

Continuous Extraction of Europium(III) by Ionic Liquid in the Rotating Disk Column with an Asymmetrical Structure Aimed at the Evaluation of Reactive Mass Transfer

In this study, the features of the solvent extraction technique were investigated to explore the potential of ionic liquid for extracting Eu(III) from aqueous solution. The transport process between the aqueous and organic phase was carried out in the rotating disk column with an asymmetrical structure and a continuous mode of operation. The utilization of Cyphos IL 104 as an ionic liquid in comparison with Cyanex272 extractant was evaluated for the extraction abilities in the recovering of Eu(III) under different conditions, including agitation speed, inlet aqueous, and solvent phase velocities. The degree of extraction and the mass-transfer rate were best when the agitation speed and the superficial velocities of aqueous and solvent phases were adjusted to 690 rpm, 0.831 mm/s, and 1.385 mm/s, respectively. The better efficiency was achieved using the ionic liquid with 0.02 mol/L concentration, 96.52% Eu(III) extraction in comparison to the same condition without the presence of ionic liquids with Cyanex272 (0.5 mol/L, 99.66%). With the analysis of the data, it was noted that the increase in the operating parameters has a positive influence on the holdup, degree of extraction, and mass-transfer rates. The percentage increase equal to 33.57% for overall mass-transfer coefficients was obtained with the increment of mixing in the column. The results showed that the mass transfer is associated with reactive resistance. The previous correlation did not explain the behavior of the system correctly in the reactive mode. Finally, the empirical models using the Sherwood number were developed to correlate the mass-transfer coefficient.