Degradation and detoxification of the wood preservatives creosote and pentachlorophenol in water by the photo-Fenton reaction

Pentachlorophenol (PCP) and the organic compounds in creosote often contaminate groundwater at wood preserving facilities. Since many of these compounds are toxic, effective water treatment technologies must be identified. In laboratory scale experiments saturated aqueous solutions of creosote and PCP were treated by the photo-assisted Fenton reaction, Fe3+/H2O2/UV ([Fe3+]=1 mM, [H2O2]=10 mM, 1.4×10−3 M hν min−1 black lamp ultraviolet light (UV), pH=2.75 and 25°C). The disappearance of 37 polycyclic aromatic hydrocarbons (PAHs), O, N and S-heterocyclic aromatic compounds and phenolic compounds and their mineralization products were monitored during a 180 min reaction period. Substantial (>90%) transformation of all compounds except a few 4- and 5-ring PAHs was achieved in 5 min, with more extensive transformation occurring thereafter. The reactivity followed the order: 2 ring PAHs>heterocyclics>phenolics>3 ring PAHs>4–5 ring PAHs. Complete dechlorination of PCP required only 10–20 min. Within 180 min the total organic carbon concentration declined by about 80% and added 9-14C-phenanthrene or 4,5,9,10-14C-pyrene were mineralized by 93% and 35%, respectively. About 33% of the organic nitrogen was converted to a 2:1 mole ratio of NH4+ and HNO3 and trace amounts of HNO2. An undetermined yield of sulfate was also generated. The acute toxicity of the treated solution to fathead minnows (Pimephales promelas) was nearly eliminated and the acute toxicity to daphnia (Daphnia pulex) was reduced. These results demonstrate the efficacy of Fe3+/H2O2/UV for removing creosote and PCP in water.