The use of sequential extraction to determine the distribution and modes of occurrence of mercury in Permian Huaibei coal, Anhui Province, China

Trace Elements in Coal Gangue: A Review

“…Similar to ion-exchangeable mercury, carbonate-bound mercury is also nearly negligible and accounts for 0.38-1.76% of the total mercury in coal gangue; this result is consistent with the other reports on coals [43,46]. Organic-bound mercury accounts for approximately 2-4% in ED and TX and less than 0.3% in GD and PL, whereas the content of organic-bound mercury almost exceeded 40% in coal [43]. This result indicates that a small portion of organic-bound mercury exists in coal gangue because of the high content of minerals and low content of organic matter in coal gangue.…”

“…Moreover, the content of ionexchangeable mercury for ED, GD, PL, and TX are calculated to be 0.91, 0.67, 0.98, and 0.27%, respectively, being almost negligible at less than 1%. Similar to ion-exchangeable mercury, carbonate-bound mercury is also nearly negligible and accounts for 0.38-1.76% of the total mercury in coal gangue; this result is consistent with the other reports on coals [43,46]. Organic-bound mercury accounts for approximately 2-4% in ED and TX and less than 0.3% in GD and PL, whereas the content of organic-bound mercury almost exceeded 40% in coal [43].…”

“…It can be seen from Table 2 that the sulfide-bound mercury is the dominant form of mercury in the four coal gangues; the levels of sulfide-bound mercury are 74.22, 51.49, 78.88, and 74.70% for ED, GD, PL, and TX, respectively; this result is similar to the results of other reports on coal [43,46]. The result also shows that the second most abundant mercury form is the silicate-bound mercury, accounting for 10.32, 20.81, 18.55, and 21.96% of the total mercury in the coal gangues of ED, GD, PL, and TX, respectively.…”

“…This method identifies trace elements species on the basis of the chemical leaching of the complex substrate, which have been proved to be an effective method in determining the modes of occurrence of trace element in the solids [43,44]. Based on sequential extraction procedures, the mode of occurrence of trace element in coal can be classified into five fractions (exchangeable, carbon bound, Fe-Mn oxides bound, organic matter bound, and residual) or six fractions (water-leachable, ion-exchangeable, organic-bound, carbonate-bound, silicate-bound, and sulfide-bound) [38,43]. Because coal gangue is similar to coal, the sequential extraction method was also preformed to determine the modes of occurrence of trace elements in coal gangue [12,38,43].…”

“…Based on sequential extraction procedures, the mode of occurrence of trace element in coal can be classified into five fractions (exchangeable, carbon bound, Fe-Mn oxides bound, organic matter bound, and residual) or six fractions (water-leachable, ion-exchangeable, organic-bound, carbonate-bound, silicate-bound, and sulfide-bound) [38,43]. Because coal gangue is similar to coal, the sequential extraction method was also preformed to determine the modes of occurrence of trace elements in coal gangue [12,38,43]. For example, the six-step sequential extraction procedure was adopted by Zhou to study the modes of occurrence of trace element in coal gangue [15].…”