We will be reporting on our continuing efforts to study the formation of environmentally persistent free radical (EPFRs) in pentachlorophenol contaminated soil. The system under study is a composite of predominantly aromatic polyphenylene ring and copper-loaded montmorillonite clay as a model of soil organic matter and clay mineral components. Phenol was employed as a precursor pollutant.  Results from TGA indicated 5% polyphenylene content, while Raman spectroscopy of the composite showed characteristic D, D' and G bands at 1342 cm-1, 1641cm-1 and 1548 cm-1, further confirming the presence of the polymer. The formation of EPFRs in Cu(II)-clay (Cu(II)CaMMT) and Cu(II)clay-polymer(PolyphCu(II)CaMMT) composite at low temperature (40 �C) was examined. The g-factor of the EPFRs formed on Cu(II)CaMMT as monitored by the EPR spectroscopy was observed to be 2.0035 at a radical concentration of 1.15 x 1017 spins/g, while inherent radical in PolyphCu(II)CaMMT showed a g-factor of 2.0024 with concentration of 5.94 x 1016 spins/g. Comparison between EPFRs formed after the phenol exposure to PolyphCu(II)CaMMT showed a shift in g-factor from 2.0024 to 2.0033, with a resultant concentration of 1.88 x 1017 spins/g indicating the presence of phenoxyl radical (EPFRs) formed through the association of phenol with the polymer component. The 1/e lifetimes of EPFRs formed revealed a decay time of ~20 hours for Cu(II)CaMMT and a split decay pattern for PolyphCu(II)CaMMT of ~17 hours for each decay time. The generation of reactive oxygen species (hydroxyl radical) by the clay-polymer composite was also investigated. High concentrations of hydroxyl radical at 2.85 x 1014 spins/mL and 2.73 x 1014 spins/mL were detected for PolyphCu(II)CaMMT and Cu(II)CaMMT respectively, after phenol exposure.

Possible routes in the low temperature formation of environmentally persistent free radicals in polymer modified copper Ccay system: A soil model system

248th National Meeting (2014)

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