Olive mill wastewater treatment by electro-Fenton with heterogeneous iron source

The production of olive oil is an added value for the Mediterranean countries, although it presents a negative impact to the environment, due to olive mill effluents, with recalcitrant properties. In this study, the degradation of olive mill wastewater (OMW) from Portuguese and Tunisian olive mills was performed by utilizing the electro-Fenton (EF) process, using as iron source commercial iron salts and mined pyrite and chalcopyrite. The EF process proved to be suitable to treat OMWs and, utilizing the most favorable experimental conditions, after 8 h assay, a chemical oxygen demand removal of 22.7 g L⁻¹ was attained. Pyrite proved to be a more efficient iron source than chalcopyrite. The use of iron-containing solid catalysts, pyrite and chalcopyrite, when compared with iron sulfate or chloride, showed to promote identical treatment results, with the advantage that they can be recovered and reutilized, since they are kept in suspension.