IRON-OXIDE SURFACE CATALYZED OXIDATION OF QUINOLINE BY HYDROGEN-PEROXIDE

The objective of this research was to examine and compare the surface catalyzed loss of quinoline, a model pollutant, in the presence of thr ee iron oxides: ferrihydrite, goethite, and a semicrystalline iron oxi de. These are ubiquitous in the subsurface environment and have been i mplicated in the possible abiotic loss of contaminants when hydrogen p eroxide is injected for augmenting bioremediation. This suggests the p ossible use of hydrogen peroxide specifically as an oxidant of some co mpounds in the subsurface. A comparison also reveals the best candidat e for use in a supported oxide fixed bed treatment system utilizing hy drogen peroxide as an oxidant. The catalytic activity toward quinoline oxidation was highest for goethite, much less for the semicrystalline material, and negligible in the presence of ferrihydrite. Several wat er constituents affected reaction rates and stoichiometry by adsorptio n or through effects on solution chemistry. The stoichiometric efficie ncy relating quinoline loss to hydrogen peroxide decomposition was not a function of oxide concentration, nor was it affected by the presenc e of carbonate or phosphate that reduced the rate of hydrogen peroxide decomposition. The effect of humic acid on quinoline loss and hydroge n peroxide decomposition rate depended on its concentration, suggestin g that it may act as a radical scavenger, radical chain promoter, and catalytic site inhibitor.