Review on adsorbents in elemental mercury removal in coal combustion flue gas, smelting flue gas and natural gas

•The discrepancy of the application environment demands different characteristics of adsorbents.•The demercuration barriers, stabilization of mercury-containing compounds and regeneration are summarized.•Structure, hydrophobic groups and modification could purposefully overcome the bottleneck of H2O and SO2.•The thermal treatment accompanied by different components has been widely adopted as an efficient approach for regeneration.