Phytoextraction of rare earth elements

Rare earth elements (REE) are a group of 17 elements with similar physicochemical properties. Most of the world’s REE extraction belongs to China. Due to the growing demand for REE and limited resources, the European Commission has identified REE as critical materials. On the other hand, little is known so far about the possible effects of long-term exposure of living organisms and the ecosystem to REE. Therefore, potential solutions for the recovery of distributed REE are being sought. Phytoextraction is a method that allows the recovery of elements from the environment. For this purpose, two strategies are gener- ally used: the use of plants with the natural ability to accumulate REE (hyperaccumulators) and the support of the process through the use of chelators. Twenty two species have been identified as REE hyperaccumulators, e.g. Phytolacca americana, Dicranop- teris linearis, Blechnum niponicum or Carya tomentosa. For the total REE, an accumulation limit of 100 mg kg-1 dry weight was established. Natural chelators are used as additives, e.g. humic acids or low molecular weight acids, as well as synthetic ones: EDTA or EGTA. In addition, the efficiency of the process is also influenced by other factors, such as the sorption capacity of the soil, the content of organic matter in the soil or soil pH. The aim of this article is to present the plant species useful in REE phy- toextraction and the potential for enhancing the method with the use of chelators.