A Wyodak coal (WD coal) and an Illinois No.6 (IL coal) were thermally extracted with N-methy-2-pyrrolidone (NMP) and 1-methynaphthalene (1-MN) to produce clean coal extract. This study has focused on the behaviors of major and trace metals with various extraction processes. It was found that the extraction with 1-MN achieved 60-100% reductions in the concentration of Li, Be, V, Ga, As, Sr, Cd, Ba, Hg, and Pb. The extraction with NMP yielded more extract than with 1-MN, but it retained more organically associated major and trace metals in the extracts. The acid pretreatment not only substantially increased the extraction yield in the extraction of WD coal with NMP but also significantly reduced the concentrations of alkaline earth elements such as Ca, Mg, Be, Sr, and Ba.
