Photodecomposition of phenol in a tubular-flow reactor

Abstract

The photodecomposition of pollutant-level concentrations of phenol in water was investigated in differential-flow and batch-recycle reactors. Initial rates were correlated in terms of a two-step process: activation to produce free radicals followed by formation of peroxides. Batch-recycle data showed that phenol can be oxidized to carbon dioxide and water and that benzoquinone is a prominent intermediate. Initial rates of decomposition of this intermediate were about four times those for phenol for the same absorption of radiation. For both phenol and p-benzoquinone initial rates were first order in light intensity and varied from first order to zero order in concentrations of reactant. The data indicate that the slow steps in the overall oxidation are the initial photoactivation of phenol and the subsequent ring-opening step. A general sequence of steps is postulated for the whole process.