Abstract: A process for the purification of acid aqueous effluent contaminated with organic material is disclosed herein. The method includes the steps of: a) bringing the aqueous effluent in contact with an iron-containing material in particulate form, wherein the particles of iron are in the metallic state; b) subjecting the material to mechanical processing in contact with the aqueous effluent while dissolving at least part of the metallic iron; c) increasing the pH of the aqueous effluent after the mechanical processing step to an essentially neutral pH; d) causing precipitation of three-valent iron under oxidizing conditions; and e) separating the precipitate from aqueous phase of step d).