Natural lemenite, after a simple magnetic separation, was investigated as a few-oost analyst in a Fenten-like system. The materials were characterized with temperature-programmed reduction (TPR), infrared spectroscopy, N-2 adsorption/desorption, and Fe-57 Mossbauer spectroscopy. Results showed that the main iron oxide phases in the materials were goethite (alpha FEOOH) and maghemite (gamma Fe2O3) before and after the magnetic separation, respectively. The catalytic tests were carried out using quinoline as a model compound because it simulates the behavior of an important class of pollutants present in the fuel, i.e., nitrogen-containig compounds from contaminated petroleum. Quinoline was found to be oxidized through a successive hydroxylation mechanism. These results strongly suggest that highly reactive hydroxyl radicals, generated during the reaction involving H2O2 on the catalyst surface, are responsible for this oxidation and confirm that the material is an efficient heterogeneous Fenton-Like catalyst.