Role of CoFe2O4 on the reactivity towards H2O2 reactions.

ULISES A. AGÚ; MARIANELA P. ZANNIER; MARCOS I. OLIVA; SANDRA G. CASUSCELLI; MÓNICA E. CRIVELLO

Segovia

Conferencia; 5th Czech-Italian-Spanish Conference on Molecular Sieves and Catalysis; 2013

In this work the effect of incorporation of Co2+ into the modified ferrite structure (MFe2O4) to increase the reactivity towards H2O2 reactions was investigated. The following MFe2O4 were obtained by calcination in air at 550º C of Layered Double Hydroxides (LDH). The LDH were synthesized through co-precitation method[1] with a theoretical molar ratio M2+/Fe3+ of 3/1, being where M2+ is Mg2+ and/or Co2+. The adopted relation ships between Co2+/Fe3+ were 0.0 (0Co), 0.2 (5Co), and 0.4 (10Co), with 0%, 5% and 10% of load of Co employed in the synthesis respectively. Two aging methods was evaluated; at room temperature (rt), (ii) and hydrothermal at 200º C (ht). The calcinated materials obtained were characterized, in order to indentify phases and structures, by X-ray diffraction (XRD), infrared spectroscopy with Fourier transform (FTIR), Diffuse Reflectance UV-visible spectroscopy (DRUVvis), Temperature-programmed reduction with H2, and inductively coupled plasma optical emission spectroscopy (ICP-OES). The physicochemical analysis suggested the presence of MFe2O4 phase dispersed over a matrix of MgO in periclase structure. The catalytic tests consisted in measuring the consumption of H2O2 at room temperature with a ratio of 53 mmol H2O2/50 mg of catalyst in a volume of 100 ml of 500 ppm, 1000 ppm and 5000 ppm of phenol. H2O2 concentration along the reaction was determined by iodometric titration. The obtained results indicated that the Co2+ species at the octahedral and tetrahedral sites in the phase ferrite [CoxMg(1-x)]Fe2O4 dispersed over a matrix of MgO, strongly affects the reactivity towards H2O2 the oxidation of phenol. In the materials without Co+2 the phase obtained was MgFe2O4, and not showed catalytic activity, suggesting that the presence of CoFe2O4 in small particles plays an important role for the activation of H2O2, which can lead to two competitive reactions, i.e. the decomposition of H2O2, or the HO? radicals production in the aqueous medium[2]. In the other hand, the presence of phenol showed a strong inhibition effect over activation of H2O2 as the phenol concentration increased to 500 and 5000 ppm.