The potency of rare earth elements and yttrium in Konawe coal ashes, Indonesia

Fly ash and bottom ash (FABA), which not utilized is considered waste, has been regarded as the promising source of rare earth elements and yttrium (REY). REY has been recognized as critical raw materials to several modern high-technology applications. This research aims to identify the potential resource of REY in FABA, by investigating FABA samples from two different coal-fired power plant (KNW-1 and KNW-2) in Konawe, Southeast Sulawesi Province, Indonesia. The geochemical compositions of coal and FABA include major elements and REY determined by ICP-MS and ICP-AES. The major elements in coal and FABA samples showed the highest concentration in SiO2, Al2O3, Fe2O3, CaO, and MgO. The individual REY contents in FABA from KNW-1 are about 17-21 times higher than in coal samples while FABA from KNW-2 are about 57-73 times higher than in coal. The total REY concentration in FABA KNW-1 ranged from 227.34-276.41 ppm while the concentration in FABA KNW-2 ranged from 278.49-356.45 ppm. The total REO content of KNW-1 FABA samples ranged from 274.08-333.45 ppm. These values are lower than the REO content of the KNW-2 FABA (335.67-429.80 ppm). The percentage critical REY (30 ≤ REYdef ≤ 51) and coefficient outlook (0.7 ≤ Cou tl ≤ 1.9), showed all FABA samples are potential for promising raw material REY.