Photo-assisted electrochemical degradation of polychlorinated biphenyls with boron-doped diamond electrodes

The capacity of the photo electro-Fenton (PEF) process to degrade a mixture of seven polychlorinated biphenyl (PCB) congeners was studied. Boron-doped diamond (BDD) sheets were used as anode and cathode in the experimental electrolytic cell that contained Na₂SO₄ 0.05 M at pH 3 as supporting electrolyte for the electro generation of H₂O₂ at the cathode. The effects of UV light intensity (254 and 365 nm), current density (8, 16 and 24 mA cm^-2) and ferrous ion dosage (0.1, 0.2 and 0.3 mM) on PCB (C₀ = 50 μg L^-1) degradation were evaluated. The highest level of PCB degradation (97%) was achieved with 16 mA cm^-2 of current density, 0.1 mM of ferrous ion and UV light at 365 nm as irradiation source after 6 h of reaction. PCB28, PCB52 and PCB101 were not detected after 0.5, 1.5 and 3 h of reaction, respectively. The degradation of PCB138, PCB153, PCB180 and PCB209 was also high (>95%). The PEF system outperformed other oxidation processes (electro-Fenton, anodic oxidation, Fenton, photo-Fenton and UV photolysis) in terms of reaction rate and degradation efficiency. These results demonstrate for the first time the degradation of PCB209, the most highly chlorinated PCB congener, by an advanced electrochemical oxidation process.