Effects of Humic Substances on the Pattern of Oxidation Products of Pentachlorophenol Induced by a Biomimetic Catalytic System Using Tetra(p-sulfophenyl)porphineiron(III) and KHSO₅

Abstract

In the presence of humic substances (HSs), the oxidative conversion of pentachlorophenol (PCP) was found to be efficiently catalyzed by tetra(p-sulfophenyl)porphineiron(III) (Fe(III)-TPPS) using KHSO5 as an oxygen donor. Ortho-tetrachloroquinone (o-TeCQ), 2-hydroxyl-nonachlorodiphenyl ether (2H-NCDE), 4-hydroxyl-nonachlorodiphenyl ether (4H-NCDE), and octachlorodibenzo-p-dioxin (OCDD) were identified as the major byproducts of the reaction. Decreased amounts of these byproducts were produced in the presence of HS. In particular, the addition of HSs with a lower degree of humification resulted in a large decrease in the formation of dimers, such as 2H-NCDE, 4H-NCDE, and OCDD. More than 60% of the chlorine, which was released from PCP, was found in the HS fractions after the reaction. This suggests that chlorinated intermediates from PCP were incorporated into the HS. Pyrolysis-GC/MS and 13C NMR studies confirmed that the binding of the chlorinated intermediates was covalent in nature and that the intermediates were copolymerized with HS via oxidative coupling reactions. A Microtox test demonstrated that the toxicity of the HS fraction containing PCP-derived intermediates was much lower than that of the mixture of PCP and HS in the absence of a catalytic reaction.

Degradation of pentachlorophenol in contaminated soil suspensions by potassium monopersulfate catalyzed oxidation by a supramolecular complex between tetra(p-sulfophenyl)porphineiron(III) and hydroxypropyl-β-cyclodextrin

“…Such oxidants can be reduced to Fe(III)-TPPS by the oxidation of PCP to a pentachlorophenoxy radical (PCP • ). The PCP • is further oxidized, giving rise to a variety of by-products are produced [10,11,13]. Prior to applying the Fe(III)-TPPS/KHSO 5 catalytic system to the degradation of PCP in contaminated soil suspensions, the influence of some matrices in the soil suspensions on the disappearance of PCP was examined.…”

“…It is known that iron(III)-porphyrins, which are regarded as biomimetic models for active sites in lignase, are able to catalyze the degradation of chlorophenols [10][11][12][13]. In general, the catalytic activities of iron(III)-porphyrins are much less sensitive to variations in environmental conditions than are microorganisms and even enzymes in vitro.…”

Decolorization of orange II by catalytic oxidation using iron (III) phthalocyanine-tetrasulfonic acid

“…The procedures used in the test have been described in a previous paper [16]. In this test, reaction mixtures were diluted with 0.02 M NaH 2 PO 4 /Na 2 HPO 4 buffer (pH 6) up to 0.17-9.27 mg l -1 of TOC, and the diluted solution was then used in the tests.…”

“…In this experiment, the concentration of toxic compounds in the solution was normalized to TOC, because AO7 could be converted to a variety of compounds via oxidation. According to previous reports [16,17], the EC 50 value was employed to compare the toxicities of the solutions before and after the reaction. All Microtox tests were conducted in triplicate.…”

“…In this test, the EC 50 values that were normalized to TOC in the solutions were employed as an index of toxicity. In general, the toxicity of a sample solution increases with decreasing EC 50 [16,17]. The EC 50 values of the solutions before and after reaction are summarized in Table 2.…”