• 标题：Organic-association of Ge in the coal-hosted ore deposits: An experimental and theoretical approach
• 关键词：High-Ge coal,Coal structure,Ge-O complex,Phenolic hydroxyl,Wulantuga,Lincang
• 作者：Qiang Wei,Chaonan Cui,Shifeng Dai

 The Wulantuga and Lincang germanium deposits in China are both giant coal-hosted Ge deposits. It is a consensus that the enriched Ge in the high-Ge coals is predominantly associated with the organics, but the specific bonding sites for Ge still remain unclear. In the present study, conventional spectral analyses (13C NMR and KBrFTIR) and the density functional theory (DFT) calculations were used to investigate the functional groups responsible for Ge accumulation in the Wulantuga and Lincang deposits.

The analytical results of the semi-quantitative NMR and FTIR suggest that the phenolic hydroxyls suffered alteration by HCl-HF treatment and are most likely the bonding sites for Ge by comparing the structures of the micronized and acid demineralized huminites from two high-Ge coals. Five acidic hydroxyl containing model compounds (catechol, phenol, ethanol, acetic acid, and benzoic acid) were selected to investigate the binding nature of Ge-O complexes, and the results indicate that phenolic hydroxyls have higher reactivity relative to other groups due to the easier exposure of oxygen by hydrogen dissociation, which is the key step for the formation of Ge-O complexes. Both the experiment and calculation results support the significance of phenolic hydroxyls for Ge fixation in the two deposits, but the present study does not exclude the possible contribution of other O-containing groups.

This study facilitates understanding the mode of occurrence of Ge in the high-Ge coals and revealing the mechanism of the organic association of Ge in the coal-hosted Ge ore deposits from the perspective of coal structure.