Degradation pathways of pentachlorophenol by photo-Fenton systems in the presence of iron(III), humic acid, and hydrogen peroxide.
The degradation characteristics and pathways of pentachlorophenol (PCP) by the photo-Fenton systems were studied in H2O2 aqueous solutions, which contained Fe(III) only [H2O2/Fe(III) system] and Fe(III) + humic acid (HA) [H2O2/Fe(III)/HA system] at pH 5.0. Although 40% of the PCP was degraded after 5 h of irradiation in the H2O2/Fe(III) system, more than 90% was degraded in the H2O2/Fe(III)/HA system. This shows that at pH 5.0 the degradation of PCP is clearly enhanced by the presence of HA in the photo-Fenton system. In the H2O2/Fe(III) system, the production of octachlorodibenzo-p-dioxin (OCDD) was detected, and 2-hydroxy nonachlorodiphenyl ether was also identified as a precursor of OCDD. However, no OCDD production was observed in the H2O2/Fe(III)/HA system. This indicates that the presence of HA represses the production of OCDD during the degradation of PCP by the photo-Fenton system. Such an effect by HA can be attributed to a reaction sequence wherein reaction intermediates derived from PCP, such as PCP., are incorporated into HA. This was verified by 13C NMR and pyrolysis-GC/MS studies.
Fukushima
M
M
National Institute of Advanced Industrial Science and Technology (AIST), 16-1 Onogawa, Tsukuba 305-8569, Japan. m-fukushima@aist.go.jp
Tatsumi
K
K
D001673:Biodegradation, Environmental; D008401:Gas Chromatography-Mass Spectrometry; D006812:Humic Substances / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D007501:Iron / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D010416:Pentachlorophenol / Q000378:metabolism* / Q000528:radiation effects; D010777:Photochemistry; D000072317:Polychlorinated Dibenzodioxins / Q000031:analogs & derivatives* / Q000378:metabolism
C045076:Fenton's reagent; D006812:Humic Substances; D000072317:Polychlorinated Dibenzodioxins; D006861:Hydrogen Peroxide; D010416:Pentachlorophenol; D007501:Iron; C018117:octachlorodibenzo-4-dioxin