Natural chelating agents from olive mill wastewater to enable photo-Fenton-like reactions at natural pH.

Graphical abstract Highlights • Very diluted Olive Mill Wastewater could be used as a natural chelating agent. • Iron (5 mg/L) is kept in solution at circumneutral pH by natural polyphenols. • Solar photo-Fenton using natural chelates could treat microcontaminants. Abstract The potential of polyphenols, present in olive mill wastewater (OMW), to act as iron chelators in photo-Fenton reaction without water acidification for the treatment of different microcontaminants in water has been studied. OMW containing 6.3 g/L of phenols has been dosed from 1:100 to 1:1500 in water containing 200 μg/L of terbutryn, chlorfenvinphos, pentachlorophenol and diclofenac. Experiments were performed in compound parabolic collector (CPC) solar pilot plant installed in Plataforma Solar de Almería using Fe 0.1 mM and H 2 O 2 50 mg L−1. The total irradiated area was 3.08 m2 and the total volume 39 L. Results indicated that iron was forming a stable complex with components of OMW along different pH values. > 90% degradation of the four microcontaminants was achieved with solar photo-Fenton at circumnetutral pH adding OMW 1:1200 for keeping iron in solution, allowing to operate a photo-Fenton process without acidifying wastewater. It leads to an alternative to using artificial-synthetic iron-complexing ligands. [ABSTRACT FROM AUTHOR]