Efficient elimination of tyrosol in a zero valent iron-EDTA system at mild conditions

• Zero valent iron, EDTA and air (ZEA) is an efficient system to remove tyrosol.
• Quasi total tyrosol conversion was attained after 2 h.
• Degradation pathway of tyrosol is similar than of the phenol.
• Degradation products of EDTA are also able to catalyse oxidation of tyrosol.
• Langmuir–Hinshelwood model was used to determine kinetics of tyrosol removal.

This study investigates the degradation of tyrosol, a major compound of the polyphenolic fraction present in olive oil mill wastewater (OMW) by means of a zero valent iron/air Fenton like system in presence of EDTA. To the best of our knowledge it is the first time that this process is entirely devoted to tyrosol and in the effect of its experimental conditions. Reaction conditions, i.e., load of iron, concentration of EDTA, temperature and initial pH, are examined. The concentration of EDTA, the load of Fe and the temperature have a great influence on tyrosol degradation. The experimental results show that tyrosol can be removed efficiently. Above 99% of tyrosol conversion was achieved after 2 h with 0.2 mM tyrosol, 0.45 mM EDTA, 90 g/L of zero valent iron at 30 °C, whereas TOC removal was 80% after 3 h at the above reaction conditions. Unlike classical Fenton, Fe-EDTA oxidation system can be used in a broad pH range, from 3 to 8. Kinetic analysis using a Langmuir–Hinshelwood (LH) model shows good fitting to the experimental data. The activation energy estimated, 37.7 kJ/mol, was close to that of other phenolic compounds. In addition, the EDTA rate constant obtained by model, 0.05 min−1 (20 °C), was in accordance with other studies. A simplified mechanism for the degradation of tyrosol is presented, where some reaction intermediates were identified.