On the photocatalytic degradation of phenol and dichloroacetate by BiVO4: The need of a sacrificial electron acceptor

The photodegradation of phenol and dichloroacetic acid (DCAA) by BiVO4 was studied in the absence as well as presence of selected electron scavengers. The experiments were performed under the visible (vis) irradiation of aqueous solutions over a wide pH range (1–13). Phenol was photocatalytically degraded by BiVO4 into p-benzoquinone below pH 3 and into an open-ring structure at pH 13. Methylene blue (MB) accelerated the reaction below the isoelectric point of BiVO4 and did not undergo significant degradation. In presence of H2O2, phenol was rapidly degraded up to pH 9. The degradation rates are two orders of magnitude higher than in absence of electron scavenger. The degradation of dichloroacetic acid was only possible in presence of H2O2. High initial concentrations of H2O2 inhibit the reaction and its consumption is very fast. Sequential additions of this sacrificial electron acceptor (SEA) enables the total degradation of a 1 mM DCAA solution.