Basics on REE
Rare Earth Elements (REE) are 17 elements including 15 lanthanides (La to Lu), scandium and yttrium. They share many of their properties, both chemical and physical and they naturally occur together in various types of mineral deposits. Rare earth elements are relatively abundant in the Earth’s crust, however they are usually not concentrated in economically exploitable ores.
Current estimates of available reserves exceed annual world production by three orders of magnitude.
REE are subdivided according to their atomic weight into light rare earths (LREE), which include La to Sm and scandium, and heavy rare earths (HREE) including Eu to Lu and yttrium. HREE are significantly less abundant in REE ores than LREE. According to the 2011 Critical Materials Report issued from the U.S. Department of Energy there are 5 critical rare earths (neodymium, praseodymium, dysprosium, terbium and europium) having the highest importance in the rapidly developing clean energy applications and with the highest risk of supply, neodymium being the largest by value and volume.
REE extraction is a technically complicated process requiring intensive processing. Mining and processing of REE-bearing materials may have serious environmental impacts. Both the leaching processes as well as the subsequent separation of the REE from other material require considerable amounts of hazardous and in some cases expensive chemicals and sometimes lead to discharge of radioactive material like e.g. uranium and thorium. Thus, in order to be able to meet the challenge and demands put on Europe in the future, it is necessary to develop clean and efficient technologies for the leaching and separation of REE in an economical way.