Estimation of rare earth elements in Indian coal fly ashes for recovery feasibility as a secondary source

Abstract

Huge amount of coal fly ash is being generated in India and the management of unutilized ash became an environmental issue due to its hazardous nature. Identification of new applications will increase its consumption which in turn reduces the environmental burden. Recently, fly ash was identified as potential secondary source to recover valuable rare earth elements. Considering this, the current study was initiated to quantify the rare earths in Indian coal fly ashes and the generated data was assessed for identifying suitable coal fly ash to recover rare earth elements. Accordingly, eight coal fly ash samples and two Indian coals were collected, acid digested and quantified for rare earths using Triple Quadruple-Inductively Coupled Plasma Mass Spectrometry. Chemical analysis results show that, Ce has highest abundance with concentration values ranging from 88±1.5 – 218±5.8 µg/g and the least concentration was observed for Lu with typical values ranging from 0.5 ± 0.02 – 0.8 ± 0.01 µg/g. Sum of all rare earth's content in analyzed samples was found in the range 234 µg/g to 533 µg/g. Coal fly ash samples, had critical REY content ≥30% (except few samples) and an outlook coefficient ≥0.7 which indicates that some samples can be used as secondary resource for rare earth elements extraction.