Partial purification of iron solutions from ripe table olive processing using ozone and electro-coagulation

This study investigates the application of electro-coagulation and ozonation technologies for the partial depuration of ferrous solutions deriving from the color fixation stage of ripe olive processing. Different operational conditions were investigated along with the possibilities of combining the two techniques sequentially. In electro-coagulation the best depuration conditions were obtained using a current density of 25 mA cm−2 for 40 min; COD elimination reached 30%, the phenols and color of the solutions were also considerably reduced and the dissolved Fe was completely removed. On the contrary, the microbial population mainly composed of lactic acid bacteria and yeasts, hardly decreased. The application of ozonation also reduced the total phenols, color and COD of solutions, but did not decrease the iron concentration. However, it considerably affected the microbial population in a higher proportion than electro-coagulation. In light of the results obtained, the best working conditions consist of applying 40 min electro-coagulation with aluminum in the anode and iron in the cathode at 25 mA cm−2 current density, followed by the storage of a partially purified solution bubbling ozone to reduce the microorganism population and even eliminate it completely when 6 g O3 L−1 were added. This would allow for a possible reuse of these solutions for preparing new fixing color solutions or as cover brine in packaging.