Project Summary (2005-2012)

This research concentrates on the development of oxidative processes for remediation of groundwater and soils/sediments contaminated with halogenated and non-halogenated organics with suspected reproductive and developmental consequences. The treatment relies on catalytic iron reagents whose mode of operation is preferably mimicking that of biological oxygenases (P-450, sMMO), and are thus more selective than other advanced oxidative technologies that make use of indiscriminate hydroxyl radicals. Specifically, this work provides new and more robust members of a family of monoiron reagents (P-450 analogs), which are supported by electron-rich tripodal ligands designed to stabilize high-valent iron-oxo oxidants and ligand-centered radicals simultaneously. In addition, a new family of diiron reagents (sMMO analogs) is being introduced to afford highly electrophilic oxidants for use in oxygenations of persistent pollutant substrates. Suitable reagents are being investigated in the degradation of a wide range of substrates, including chlorinated solvents, BTEX, phthalates, MTBE and chlorophenols, as well as against recalcitrant lipophilic substrates such as polychlorinated dibenzo-p-dioxins, dibenzofurans and biphenyls. Mechanistic studies associated with metal, ligand, and substrate-centered events are being pursued to report on the suitability of the reagents at hand and evaluate their biomimetic mode of action. The mechanistic work is also expected to provide insights in relation to the currently debated oxygenation pathways of biological oxygenases (P-450, sMMO). The most successful reagents become the subject of bench-scale, column treatability studies in sequential reductive (Fe(0)) and oxidative treatment zones designed to effect complete degradation of organic contaminants. The oxidative zone is composed of the oxygenation reagents developed in this study, suitably modified to afford heterogerized versions of the catalysts supported on inert matrices. The effectiveness on chemical mixtures is being studied in detail.