Effect of Hydroxypropyl-β-cyclo-dextrin on the Degradation of Pentachlorophenol by Potassium Monopersulfate Catalyzed with Iron(Ⅲ)—Porphyrin Complex

摘要

A novel biomimetic catalytic system containing a supramolecular complex between iron(Ⅲ)—tetrakis(p-sulfonatophenyl)porphyrin [Fe(Ⅲ)-TPPS] and hydroxypropyl-β-cyclodextrin (HP-β-CD) was examined for the potassium monopersulfate catalyzed oxidation of pentachlorophenol (PCP). In the absence of HP-β-CD, the percentage of PCP disappearance and the numbers of chlorine atoms released from PCP increased to 50% and 1.5 for a 1-day reaction period, respectively. However, in the presence of HP-β-CD, the PCP completely disappeared and the number of chlorine atoms from PCP was increased to 3.1. o-Tetrachloroquinone, 2- and 4-hydroxyl-nonachlorodiphenyl ethers, and octachlorodibenzo-p-dioxin were detected among the oxidation products. In the absence of HP-β-CD,the percentage of PCP conversion to oxidation products increased and then reached plateau. In the presence of HP-β-CD, the amount of oxidation products produced initially increased for the first 10 min and thereafter decreased gradually. These results suggest that the addition of HP-β-CD results in the further degradation of oxidation products. In addition, the mineralization of PCP to CO_2 was investigated using ~(14)C_6-labeled PCP. After a 1-day reaction period, 24% of the ~(14)C_6-labeled PCP was converted to ~(14)CO_2 in the presence of HP-β-CD, although significant ~(14)CO_2 generation was not observed in its absence. The effect of HP-β-CD on the facilitation of PCP degradation can be attributed to the fact that the self-oxidation of Fe(Ⅲ)—TPPS is prevented by the formstion of a stable supramolecular complex between HP-β-CD and Fe(Ⅲ)-TPPS.