Destruction of 2,4-Dichlorophenol in Aqueous Solution over Salen-Porphyrin Complex

Abstract

In present study, a salen-porphyrin complex ZnPSC6 was utilized for improving destruction and detoxification of 2,4-dichlorophenol (2,4-DCP) as it is a binuclear biomimetic complex and has two active sites within one complex as well as high catalytic selectivity and efficiency owing to the combined property of salen complex, porphyrin complex, and biocatalyst. The objectives of the study were to use ZnPSC6 as a catalyst to degrade 2,4-DCP and to study its impact on the toxicity of 2,4-DCP aqueous solution. The conversion of 2,4-DCP was followed by high-performance liquid chromatography (HPLC), liquid chromatography-time of flight-mass spectrometry (LC-TOF-MS), total carbon content (TCC) determination, and ecotoxicity evaluation. Catalysis with ZnPSC6 for 2,4-DCP oxidation by hydrogen peroxide (H2O2) improved the destruction and detoxification of 2,4-DCP in aqueous solution in comparison to salen complex Zn(salen) and porphyrin complex Zn(Phe-TPP). When ZnPSC6 was incorporated into the catalytic oxidation of 2,4-DCP in an aqueous solution of pH 8 at 30°C for 30 min, the conversion of 2,4-DCP was found to be ~100%, very high in comparison to Zn(salen) and Zn(Phe-TPP). A considerable decrease of TCC in 2,4-DCP aqueous solution was observed on adding the ZnPSC6 catalysis compared to Zn(salen) and Zn(Phe-TPP). The TCC values of the ZnPSC6-, Zn(salen)- and Zn(Phe-TPP)-treated 2,4-DCP aqueous solutions were found to be 0.17, 0.51 and 0.42%, respectively. Also, the ecotoxicity of the 2,4-DCP aqueous solution was reduced significantly with ZnPSC6 catalysis. While the ecotoxicity of the 2,4-DCP aqueous solution was 1.14 T.U. after treatment by ZnPSC6 catalysed oxidation, that was 8.18 and 5.53 T.U. for Zn(salen) and Zn(Phe-TPP), respectively. These promotion effects were confirmed in terms of degradation products as determined with LC-TOF-MS. This could suggest a promising process for chlorophenol mineralization.