Monopersulfate oxidation of tetrabromobisphenol A by biomimetic catalysts supported on cation- and anion-exchange resins

Iron(III)-porphyrin complexes, regarded as biomimetic models for oxidative enzymes, catalyze the degradation of a tetrabromobisphenol A (TBBPA) derivative that is distributed in landfills. To suppress the deactivation of the catalyst via self-degradation and dimerization, iron(III)-tetrakis(1-methylpyridinium-4-yl)porphyrin (FeTMPyP) and iron(III)-tetrakis(4-sulfonatephenyl)porphyrin (FeTPPS) were supported on cation- (FeTMPyP/CER) and anion-exchange (FeTPPS/AER) resins, respectively, and their catalytic activity and durability were examined in the absence and presence of humic acid (HA), which is major component of landfill leachates. The FeTPPS/AER catalyst had a fast reaction rate for TBBPA degradation, but decolorized quickly and had no reusability. In contrast, the FeTMPyP/CER catalyst was highly durable, catalyzing the degradation of over 90% of the TBBPA and no bleaching was observed in the FeTMPyP/CER catalyst after ten recyclings. Thus, the FeTMPyP/CER catalyst can be considered to be a biomimetic model of oxidative enzymes in landfills. 4-(2-Hydroxyisopropyl)-2,6-dibromophenol (2HIP-2,6DBP) was the major oxidation product, both in the absence and presence of HA. In the absence of HA, the coupling compound between a TBBPA radical species and 2,6-dibromophenol, which is more toxic than the parent compound, was detected. However, this formation was suppressed in the presence of HA.