Mesoporous manganese oxide for the degradation of organophosphates pesticides

Abstract

Manganese(IV) oxide used for degradation of toxic organophosphorus compounds was prepared by homogeneous hydrolysis of potassium permanganate (KMnO4) with 2-chloroacetamide. The prepared sample was characterized by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and nitrogen physisorption. The degradation efficiency was determined with parathion methyl (PM) as representative of organophosphate pesticides using high-performance liquid chromatography. For a comparison, the commercially obtained product and the two synthesized manganese(IV) oxides prepared by direct reaction of manganese(II) sulfate (MnSO4·H2O) and potassium permanganate (KMnO4) and potassium permanganate (KMnO4) with urea in aqueous solution were tested. The sample prepared by homogeneous hydrolysis of KMnO4 with 2-chloroacetamide showed the highest degradation efficacy. The reaction half-time in non-polar organic solvent (n-heptane) was around 0.9 min with the degradation efficiency of about 90 % within 2 h. It was shown that comparative samples of manganese(IV) oxides were variously effective in decomposition of PM by cleavage of the P–O-aryl bond in the pesticide molecule. The degradation mechanism for PM on the MnO2 surfaces was proposed.