A flue gas purification device comprising a scrubbing liquid sump (16), which comprises: an oxidation device (24) having at least one pipeline (21) and oxygen outlets (22) provided therein for introducing oxygen into said scrubbing liquid sump (16), and circulation means (28) for circulating the scrubbing liquid present in said scrubbing liquid sump (16) inside said scrubbing liquid sump (16), characterized in that said oxygen outlets (22) of the at least one pipeline (21) of said oxidation device (24) have a diameter of least 9 mm.