Tetradentate amide extraction agents for trivalent lanthanides

Doctoral thesis, 2018

Lanthanides are valuable materials. They are used in catalysts, permanent magnets, batteries, optical devices, and in many other products. Lanthanides are mainly supplied by mining industry, which generates large volumes of waste due to relatively low concentrations of these elements in geological deposits. Recovery of lanthanides from end-of-life items could contribute to the supply of these elements and thus decrease waste generation from mining.

Solvent extraction is the dominant method for separation of lanthanides on commercial scale. It can also be used in hydrometallurgical recovery of lanthanides from waste streams. One disadvantage of current extraction processes is the need to use a large number of separation stages and, accordingly, large amount of chemicals. The extractants with the enhanced affinity for lanthanides could remedy this problem.

In this work novel tetradentate amide extractants, designed and synthesized for extraction of lanthanides, are reported. The distribution ratios of lanthanides were found to be higher in the reactions with these amides than with the bidentate malonamides. This is due to a difference in the entropic effects, associated with the extraction of the metals by the malonamides and the new reagents. Solvent extraction, X-ray crystallography and mass spectroscopy have been used to investigate the interactions of f-block elements with the new extractants.