Degradation and detoxification of the wood preservatives creosote and pentachlorophenol in water by the photofenton reaction

Pentachlorophenol (PCP) and the organic compounds in creosote often contami nate groundwater at wood preserving facilities. Since many of these compoun ds are toxic. effective water treatment technologies must be identified. In laboratory scale experiments saturated aqueous solutions of creosote and P CP were treated by the photo-assisted Fenton reaction, Fe3+/H2O2/UV ([Fe3+] = 1 mM, [H2O2] = 10 mM, 1.4 x 10(-3) M hv min(-1) black lamp ultraviolet l ight (UV), pH = 2.75 and 25 degrees C). The disappearance of 37 polycyclic aromatic hydrocarbons (PAHs), O, N and S-heterocyclic aromatic compounds an d phenolic compounds and their mineralization products were monitored durin g a 180 min reaction period. Substantial (> 90%) transformation of all comp ounds except a few 4- and 5-ring PAHs was achieved in 5 min, with more exte nsive transformation occurring thereafter. The reactivity followed the orde r: 2 ring PAHs > heterocyclics > phenolics > 3 ring PAHs > 4-5 ring PAHs. C omplete dechlorination of PCP required only 10-20 min. Within 180 min the t otal organic carbon concentration declined by about 80% and added 9-C-14-ph enanthrene or 4,5,9,10-C-14-pyrene were mineralized by 93% and 35%, respect ively. 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 sulfat e 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 effi cacy of Fe3+/H2O2/UV for removing creosote and PCP in water. (C) 1999 Elsev ier Science Ltd. All rights reserved.