Kinetics of competitive ozonation of some phenolic compounds present in wastewater from food processing industries

Ozonation of four phenolic compounds found in wastewater effluents from food manufacturing processes: Gallic (G-Ac) and p-hydroxybenzoic (pHB-Ac) acids, (+)-catechin ((+)-Cat) and tyrosol (Ty), has been carried out in ultrapure water. The results showed that the direct reaction between ozone and the organic compound seems to be the exclusive way of phenolic compounds elimination. A kinetic study of these reactions was completed by using a high concentration of phenolic substances (up to 3 g L-1 total phenolic content) to simulate typical amounts of these compounds found in real wastewater. By means of a competitive method, rate constants of the direct reaction with ozone were determined at different pH. The following reactivity was found depending on pH: pHB-Ac < Ty < G-Ac < (+)-Cat in acidic conditions, pHB-Ac Fa Ty < G-Ac < (+)-Cat in neutral conditions and pHB-Ac approximate to Ty for basic conditions. Finally, validation of the calculated rate constants was completed by checking the kinetic regime in which competitive reactions were developed.