Homogeneous and heterogeneous catalysts of Fe3+, Co2+ and Cu2+ for the degradation of methyl parathion in diluted aqueous medium

Abstract

Degradation of pesticides (plaguicides, herbicides, fungicides, among others) in aqueous media is a subject of great importance for ensuring the water quality into numerous hydric sources. This work reports the assessment of homogeneous (metal ion solutions) and heterogeneous (oxides supported on alumina) systems that are based on Fe3+, Co2+ y Cu2+, which were used as catalysts for oxidation (degradation) of methyl parathion (a plaguicide) in aqueous solution. Hydrogen peroxide was herein used as oxidizing molecule under mild condition of reaction (25 ºC and atmospheric pressure). The solids were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Fe3+/H2O2 (Fenton system) was the most active homogeneous catalyst compared to Co2+/H2O2 and Cu2+/H2O2 systems. Solids catalysts such as cobalt, copper or iron oxides as well as mixed oxides supported on alumina were active at pH close to neutrality. Fe-Co-Cu/Al2O3, Co-Cu/Al2O3 and FeCo/Al2O3 mixed systems were solids with the highest catalytic activity. In addition, an important effect of the support (-Al2O3) on the reaction pH was observed, allowing to reach values close to that of the neutrality, and thus increasing the catalytic activity of both cobalt oxide and copper oxide species. These results allow advancing on a new pathway for searching catalysts to remove organophosphorous pesticides from residual waters.

Keywords

• Methyl parathion degradation
• iron oxide
• cobalt oxide
• copper oxide
• heterogeneous catalysts