A wet gas scrubber liquor and method of using the same to remove mercury from flue gases. The wet gas scrubber liquid is an alkaline liquid suspension of ferrous sulfide particles that can be prepared by combining together a ferrous ion source such as ferrous chloride, a sulfide ion source such as sodium hydrosulfide and an alkalinity source such as sodium hydroxide. When used to scrub flue gases to remove mercury from flue gases the mercury reacts with said alkaline liquid suspension of ferrous sulfide particles and can be removed by at least one of: i) adsorption onto said ferrous sulfide particles; ii) adsorption onto iron (hydr)-oxides that form in said alkaline liquid suspension of ferrous sulfide particles; and iii) absorption by reacting with sulfur formed in alkaline liquid suspension of ferrous sulfide particles and forming mercuric sulfide as a precipitate.