Mercury Capture and Control in Coal-Fired Power Plants

Coal combustion in power generation remains a principal source of anthropogenic mercury emissions, with elemental mercury (Hg0) constituting the majority of releases due to its volatility and low chemical reactivity. Upon cooling of flue gas, Hg0 can be oxidised to divalent mercury (Hg2+), which is more soluble and amenable to capture. Contemporary control strategies combine combustion optimisation with post-combustion measures, including selective catalytic reduction (SCR) for mercury oxidation, electrostatic precipitators (ESP) and fabric filters for particulate-bound mercury removal, and wet flue gas desulfurisation (WFGD) systems to absorb oxidised species. The efficiency of these devices varies widely, particularly for Hg0, prompting the development of advanced sorbents and catalysts. Innovations in material design—ranging from tailored carbonaceous adsorbents to transition metal–based catalysts—have driven considerable improvements in uptake capacity, reaction kinetics and tolerance to competing flue-gas constituents. Scaling such technologies presents both technical and economic challenges but carries significant potential for global emissions abatement.

Research from Nature Portfolio

Recent studies have demonstrated that in situ acid etching of transition metal sulfides generates defective surface and pore architectures that dramatically enhance Hg0 accommodation capacities by more than two orders of magnitude. The etched materials exhibit abundant active sites that promote surface adsorption and facilitate mercury diffusion throughout the sorbent matrix. Importantly, the etching approach is simple, scalable and applicable to a range of sulfide chemistries, offering a versatile platform for industrial-scale mercury capture.

Mercury Capture and Control in Coal-Fired Power Plants publication trend

The graph below shows the total number of articles in mercury capture and control in coal-fired power plants across all publications each year (not limited to Nature Index journals).

Technical terms

Elemental mercury (Hg0): Mercury in its zero-oxidation state, existing as a volatile gas that is challenging to remove from flue streams.

Divalent mercury (Hg2+): Oxidised mercury species, typically water-soluble, which can be captured efficiently in wet scrubbing systems.

Sorbent: A solid material engineered to adsorb or absorb pollutants, such as mercury, from flue gases.

Biochar: Porous, carbon-rich material produced by thermal decomposition of biomass under limited oxygen, used as an economical sorbent.

Flue gas: The exhaust emitted from coal combustion, containing a mixture of gaseous pollutants (mercury, SO2, NOx) and particulate matter.

References

1. In situ acid etching boosts mercury accommodation capacities of transition metal sulfides. Nature Communications (2023).
2. Regulated adsorption sites using atomically single cluster over biochar for efficient elemental mercury uptake. Biochar (2023).
3. Amorphous Molybdenum Selenide Nanosheet as an Efficient Trap for the Permanent Sequestration of Vapor‐Phase Elemental Mercury. Advanced Science (2019).
4. Influences of Copper(II) Chloride Impregnation on Activated Carbon for Low-Concentration Elemental Mercury Adsorption from Simulated Coal Combustion Flue Gas. Aerosol and Air Quality Research (2017).
5. Mercury transformation and speciation in flue gases from anthropogenic emission sources: a critical review. Atmospheric Chemistry and Physics (2016).