KINETIC AND MICROSCOPIC STUDIES OF REDUCTIVE TRANSFORMATIONS OF ORGANIC CONTAMINANTS ON SYNTHETIC GOETHITE AND NATURAL SEDIMENTS

摘要

Iron oxide minerals mediate the transformation of many prevalent contaminants in both natural environments and in engineered systems. As such reactions proceed, the size, morphology and even the phase of iron oxide minerals can change, which can result in substantial changes in reactivity. Our previous work demonstrated that degradation of 4-chloronitrobenzene (4-Cl-NB) and trichloronitromethane (TCNM) resulted in goethite growth only along the c-axis as quantified using transmission electron microscopy (TEM) for particle size and distribution analysis. Also, the reactivity decreased with each injection of organic compound and Fe(II) as shown by decreasing first-order rate constants for both the contaminant degradation and Fe(II) consumption in sequential-spike batch experiments. Here, we extend prior work by examining the degradation of five organic contaminants that reductively degrade by different mechanisms: 4-Cl-NB, tribromoacetic acid (TBAA), oxamyl, benzoquinone (BQ) and azo dyes (Orange II). Finally, we compare the results from a natural sediment with those obtained for synthetic goethite.