Ecological and Health Risks Attributed to Rare Earth Elements in Coal Fly Ash

Abstract

The occurrence and distribution of yttrium and rare earth elements (REYs), along with major elements and heavy metal(loid)s (HMs) in coal fly ash (CFA) from five coal-fired power plants (CFPPs), were analyzed, and the REY-associated ecological and health risks were assessed. The individual REYs in CFA were abundant in the following order: Ce > La > Nd > Y > Pr > Gd > Sm > Dy > Er > Yb > Eu > Ho > Tb > Tm > Lu. The total REY content ranged from 135 to 362 mg/kg, averaging 302 mg/kg. The mean light-to-heavy REY ratio was 4.1, indicating prevalent light REY enrichment in CFA. Significantly positive correlations between the REYs suggested that they coexist and share similar origins in CFA. REYs were estimated to pose low to moderate ecological risks, with risk index (RI) values ranging from 66 to 245. The hazard index (HI) and target cancer risk (TCR) of REYs from CFA, estimated to be higher for children (HIc = 0.15, TCRc = 8.4 × 10−16) than for adults (HIa = 0.017, TCRa = 3.6 × 10−16), were well below the safety limits (HI = 1, TCR = 1.0 × 10−6). However, the danger to human health posed by HMs in the same CFA samples (HIc = 5.74, TCRc = 2.6 × 10−4, TCRa = 1.1 × 10−4) exceeded the safe thresholds (excl. HIa = 0.63). The mean RI and HI attributed to REYs in CFA were 14% and 2.6%, respectively, of the total risks that include HMs.

Recovery of Rare Earth Elements from Coal Fly and Bottom Ashes by Ultrasonic Roasting Followed by Microwave Leaching

“…CFA is a waste stream generated during combustion in thermal power plants (TPPs). Through its disposal, a harmful environmental impact is manifested by the potential release of contaminants (dominantly heavy metals) into the water, air, and soil [15][16][17]. The disposal of this waste stream does not adhere to the waste management hierarchy because it contains valuable materials [18].…”

“…Fly and bottom ashes were screened using XRF spectrometry, whereas major and REE elements were quantitatively determined using inductivity-coupled plasma and optical emission spectrometry (ICP-OES) and inductivity-coupled plasma and mass spectrometry (ICP-MS), as detailed elsewhere [16]. The morphology and particle size distribution were determined using an optical microscope.…”

Extraction of Coal Concentrate From Coal Processing Waste as a Preparation Step for Separation of Rare and Rare Earth Elements

“…Одновременно отмечается рост потребности в углях и угольных концентратах с зольностью до 20% [3]. Помимо этого, данные отходы можно рассматривать как комплексные руды из-за наличия в них рассеянных, ред ких и редкоземельных элементов в промышленно значи мых концентрациях [8,9,10,11,12].…”