Extraction of rare earth elements from waste products of phosphate industry

Rare earths are critical elements in our modern societies and the ever-increasing demand raises fears of supply risks in the coming years. This work dealt with the feasibility of extracting rare earth elements (REEs) from an industrial waste product from the exploitation of phosphate ores of Djebel Onk in Te & acute;bessa eastern region of Algeria. The solid residue was first leached at room temperature with three different inorganic acids (HNO3, H2SO4 and H3PO4) at various concentrations and leaching times. It was possible to recover almost 100% of La, Ce, Eu, Gd and Y with HNO3 3 N in 24 h. However, only about 10% of Yb were leached. The leachates were further treated with two organophosphorous extractants, trioctylphosphine oxide (TOPO) and di-(2-ethylhexyl) phosphoric acid (D2EHPA) at various concentrations in chloroform. A virtually total extraction of Eu, Gd, Y and Yb was achieved with TOPO at 0.3 M. The extraction efficiency of light rare earth elements (LREEs), La and Ce, was only 38 and 55%, respectively. Very good selectivities between heavy rare earth elements (HREEs), and LREEs as well as between medium rare earth elements (MREEs) and LREEs were obtained but TOPO was unable to selectively separate HREEs from MREEs. Although D2EHPA led to lower REEs extraction efficiency than TOPO, it showed interesting performance for the selective separation of REEs into three fractions corresponding to LREEs (La and Ce), MREEs (Eu and Gd) and HREEs (Y and Yb).

Automated summary

This study experimentally validated the feasibility of extracting rare earth elements from industrial waste, identified optimal extraction conditions and methods, and investigated the effects of two organic phosphorous extractants in the separation process of rare earth elements.