Provided is a process for controlling heavy metal (e.g., mercury) emission in S02-containing flue gas, comprising passing a stream of the flue gas (2) through a wet scrubber (1) where it is brought into contact with a liquid absorbent (8) comprising an ionic liquid, an oxidizer (11) and polar protic organic solvent, wherein the amount of said organic solvent is adjusted such that the SO2 absorption is minimized while operating said wet scrubber at a temperature lower than the normal working temperature that would be used in the absence of said solvent. The process may be preceded by an initial stage where a fluoride-containing liquid is used for reducing the amount of sulfur dioxide in the flue gas stream; the sulfur dioxide can be subsequently desorbed from the fluoride-containing liquid upon the addition of a polar solvent.