Modes of occurrence of beryllium in the Ge-rich coal deposit, Lincang, SW China: Theoretical insight into organic association and distribution.

The coal-hosted germanium (Ge) deposit in Lincang, China, contains an abnormally high concentration of beryllium (Be), which is of significant organic affinity. However, the specific species of Be at the atomic scale remain unclear. In this study, thirteen model compounds representing O/S/N-containing functional groups in coal were calculated to probe the local environment of Be. The results indicate that hydroxyl and carboxyl groups are the primary acceptors of Be. Various Be-O complexes with a saturated four coordination of Be can achieve best stabilization. In contrast, the heteroatoms S and N are less likely to act as the acceptors for Be. In addition, the calculation results provide theoretical insights into the vertical distribution of Be. Unlike the upper coal seam, a fraction of Be in the middle and lower seams occurs in a mineral phase, which can be attributed to the limited capacity of organic matter to bond with all available Be. Furthermore, competition from other organically-associated metals, such as Ge and W, for bonding sites affects the local distribution of Be. This study reveals the molecular mechanism for Be enrichment in the organic matter of the Lincang Ge deposit, and suggests potential strategies for the removal of organically bonded Be in coal through the destruction of O-bridged complexes.