Photocatalytic degradation of 4-chlorophenol. 1. The hydroquinone pathway

Complete mineralization of 4-chlorophenol in water can be achieved by photo catalytic degradation of oxygenated solutions containing suspended TiO2. Th e chemical pathways of this degradation are complex, and in this paper, tha t which begins with hydroquinone is examined. Hydroxylation to form 1,2,4-b enzenetriol is the first step, though a very small amount of cleavage of th e C1-C2 bond is observed. The first major group of acyclic compounds derive s from oxidative cleavage of either the C1-C2 or C3-C4 bond of 1,2,4-benzen etriol. It is argued that this results from single electron oxidation and c apture by superoxide. Many smaller compounds have also been identified, and routes to various ones of them are proposed. Nearly all of the compounds a re verified by use of authentic samples.