Catalytic oxidation of phenol by hydrogen peroxide over a pillared clay containing iron. Active species and pH effect

Abstract

The study of the catalytic behavior of phenol oxidation by hydrogen peroxide in presence of iron has shown that both heterogeneous and homogeneous catalytic systems behave similarly. For both systems, the reaction has been found sensitive to the pH, the highest phenol conversion and TOC abatement being obtained at a pH value close to 3.7. However, the heterogeneous catalytic system appears to be less sensitive to the pH and more efficient in TOC abatement than the homogeneous one. The measurement of OH° (h) production by an ESR spin trapping technique using DMPO as trapping agent strongly suggests that the main active species are hydroxyl (OH°) and/or hydroperoxyl (HO₂°) radicals. The very low amount of iron dissolved by the reaction (less than 2% of the initial content) after more than 350 h of work in a continuous flow reactor is a very promising result to develop a catalytic continuous flow process for industrial wastewater purification.