Abstract: There is disclosed a process for separating iron, zinc and lead from flue dust and/or flue sludge, wherein the three following reaction stages are performed in the aqueous phase:A. Oxidation of the iron and filtration of the resulting first turbid liquid;B. Suspension and acidification of a first filtration residue and subsequent filtration of the resulting second turbid liquid, whereby a second filtration residue containing mainly iron sludge is obtained;C. Neutralization of the filtrate and subsequent filtration of the resulting third turbid liquid, whereby a third filtration residue containing the precipated heavy metals is obtained.