A mild photochemical approach to the degradation of phenols from olive oil mill wastewater

Photooxidation of cathecol ( 1) is carried out in aqueous solution at λ>300 nm using different sensitizers: rose bengal (RB), 9,10-dicyanoanthracene (DCA), 2,4,6-triphenylpyrylium tetrafluoroborate (Pyryl). The highest degradation is observed in the UV/RB-sensitized reaction (66% after 15 h of irradiation), mineralization and formation of dimers are the final events. This procedure has been extended to tyrosol ( 2), caffeic acid ( 3), vanillic acid ( 4), 4-hydroxycinnamic acid ( 5) and 4-hydroxybenzoic acid ( 6) as well as to a mixture of all phenols. A reduced toxicity of the UV/RB-irradiated solutions of cathecol and tyrosol towards alga Ankistrodesmus braunii is also verified.