Arsenic and antimony removal by oxidative aqueous leaching of IGCC fly ash during germanium extraction

•The leaching of IGCC fly ash was carried out using oxic conditions.•Oxidative aqueous leaching diminishes the leachability of As, Sb and Ni.•Neoformation of Fe-(oxy)hydroxides proved to be the limiting step of the process.•Adsorption on Fe-(oxy)hydroxide structures have been proposed as the mechanism.•Optimum conditions of leaching allows to remove 97% of As and 50% of Sb.