Tracing rare earth elements in oil shale ash

Abstract

Oil shale ash generated from different locations in Jordan was investigated for rare earth elements (REE). The oil shale samples were combusted at 950 °C, and then milled to less than 74 μm. The resulting fine oil shale ash samples were acid-digested to remove minerals. The acid-digested residues were analyzed using inductively coupled plasma mass spectrometry. Fifteen REEs, along with yttrium and scandium, were detected, except for promethium. Among the detected metals, the highest concentrations were found for lanthanum and cerium, at 16.3 and 10.5 ppm, respectively, in the El-Lajjun deposits. The maximum concentration of REEs was 74.4 ppm in the Al-Shalaleh region, with a combined total of 47.06 ppm for light rare earth elements (LREE) and 29.31 ppm for heavy rare earth elements (HREE). The maximum calculated LREE/HREE ratio was 2.42 ppm in the Sultani region. The yttrium and scandium concentrations were 21.3 and 2.51 ppm in the El-Lajjun and Al-Shalaleh regions, respectively.

Keywords

• rare earth elements
• oil shale ash
• icp–ms
• acid digestion.