Characterization of eluent by hot water extraction of coals in terms of total organic carbon and environmental impacts

Powdered coal samples were extracted by a hot water extraction (HWE) process, and the determination of total organic carbon (TOC) in the HWE eluent was performed by a TOC analyzer. The degree of TOC in the eluent greatly varied with kind of coals, and it tended to increase as the O/C value of coal increased. By use of heat-treated coals, which had somewhat smaller specific surface areas compared to the raw coals, it was shown that the degree of TOC in the eluent was also affected by specific surface area of coal. Almost no leaching was observed for hazardous heavy metals. The environmental impacts of the extract from the HWE eluent were evaluated by the Ames Salmonella mutagenicity assay and the estrogen receptor binding assay. The extracts from the HWE eluent did not show any notable mutagenicity. However, the extract from the HWE eluent for a lignite provided an appreciable affinity to estrogen receptor.