Kaolinite-rich Cretaceous clay sediment samples from Burgos (Spain) have been analyzed by elemental analysis, X-ray fluorescence, inductively coupled plasma mass spectrometry, X-ray diffraction and different spectroscopic techniques, as Fourier Transform Infrared, ultraviolet–visible and electron paramagnetic resonance. The clay sediment samples mainly contain quartz, muscovite and kaolinite. Different radicals, as A- and B-Centers in kaolinite and organic paramagnetic species, are detected. An illite/kaolinite FTIR band ratio parameter (IKB) is proposed to infer the illite/kaolinite proportion, which can be useful to graphically visualize the iron-substituted Al(III) sites. Studies of the activity as scavengers of DPPH and ABTS radicals show that samples with a larger amount of orthorhombic Fe(III) ions replacing Al(III) ions exhibit a higher antioxidant capacity.
