Doctoral defence: Silvester Jürjo „Separation of rare earth elements from Estonian phosphorite ore using liquid extraction followed by electrochemical reduction“

On December 20th Silvester Jürjo will defend his thesis „Separation of rare earth elements from Estonian phosphorite ore using liquid extraction followed by electrochemical reduction“. 

Supervisors: 
Professor Enn Lust, Institute of Chemistry, University of Tartu
Research fellow Ove Oll, Institute of Chemistry, University of Tartu

Oponent: 
Professor Pawel J. Kulesza, University of Warsaw, Poland

Summary
Rare earth elements (REEs) are strategic critical materials as the REEs, its alloys and compounds possess important technological properties and therefore REEs are applicable in many areas of modern energy technology. Since the demand for some REE can be estimated, there might be a supply risk. This thesis focuses on development of novel recovery method of REE from Estonian phosphorite ore using liquid extraction followed by electrochemical separation.  
Liquid extraction is a chemical separation method when two immixible liquid phases are brought into the contact and some elements transfer from one phase to another. By changing the extraction conditions, extraction results can be tuned in a desirable way.  
Electrodeposition is a method of gathering different elements into a working electrode during electrochemical reduction. Electrodeposition results can mainly be tuned by electrolyte composition and applied voltage.  
The different combined processes were characterized by inductive coupled plasma spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy, chronoamperometry, energy-dispersive X-ray spectroscopy, atomic emission spectrometry  and scanning electron microscopy.  

Two novel methods has been developed as a result:
•    Two-step liquid extraction method for separation of radioactive and  rare earth elements
•    Electrochemical method for yttrium seperation from phosphorite ore