Iron Complexes Take On Problematic Pesticides

Iron(III) tetraamido macrocyclic ligand (TAML) complexes developed by Terrence J. Collins and his research group at Carnegie Mellon University increase the oxidizing power of hydrogen peroxide under mild conditions, making the inexpensive catalysts useful for many environmental cleanup processes. Some examples include treating pulp and paper processing by-products; reducing sulfur in fuels; deactivating bacterial spores; and degrading trace amounts of bisphenol A, estrogens, and active pharmaceutical ingredients in wastewater.

In a new application, Collins and his coworkers report, TAML catalysts can completely degrade the thiophosphate triester pesticides fenitrothion, parathion, and chlorpyrifos methyl, which are under scrutiny as hormone-disrupting chemicals (J. Am. Chem. Soc., DOI: 10.1021/ja064017e).

Standard chemical and enzyme-mediated hydrolysis processes used to detoxify pesticide stockpiles or clean up contaminated sites produce hydrosylates that often contain toxic degradation compounds that require further treatment, Collins notes. The low-toxicity TAML catalysts, used at micromolar concentrations, quickly convert the pesticides primarily to low-toxicity small organic acids, dimethyl phosphate, SO₄^2???, NO₂^???, and NO₃^???.

The development is one of the first examples of "deliberately producing a highly effective degradation procedure for an endocrine-disrupting chemical with the hope that it might eventually be used for environmental protection," Collins says.