Effects of peat humic acids on the catalytic oxidation of pentachlorophenol using metalloporphyrins and metallophthalocyanines

Iron(III)-tetra(p-sulfophenyl)porphine (Fe(III)-TPPS), manganese(III)-5,10,15,20-tetra(4-pyridyl)-21H,23H-porphine (Mn(III)-TPyP), iron(III)-phthalocyanine-tetrasulfonic acid (Fe(III)-PcTS) and copper(II)-phthalocyanine-tetrasulfonic acid (Cu(II)-PcTS) were evaluated in terms of the catalytic activity for the oxidation of pentachlorophenol (PCP). Although Cu(II)-PcTS had no activity, 40-70% of the PCP was oxidized in the Fe(III)-TPPS, Fe(III)-PcTS and Mn(III)-TPyP systems. In addition, the effects of the addition of peat humic acids (HAs) on PCP oxidation were also investigated. In the presence of HAs, 65-85% of the PCP was oxidized in the Mn(III)-TPyP system, and approximately 100% of the PCP was oxidized in the Fe(III)-TPPS and Fe(III)-PcTS systems. These results show that the addition of peat HAs is effective in enhancing the PCP oxidation. The effects of peat HAs were investigated using hydroxypropyl-p-cyclodextrin (HP-P-Cl)) as a model for the hydrophobic portions in HAs, because peat HA contains a hydrophobic core similar to that of cyclodextrin. The conversion of PCP increased with increasing concentrations of HP-P-CD. This suggests that structural moieties analogous to cyclodextrins in peat HAs contribute to the enhanced PCP oxidation via the catalytic system with Fe(III)- and Mn(III)-complexes. (C) 2004 Elsevier B.V. All rights reserved.