Manganese dioxide nanoparticles-silver-Y zeolite as a nanocomposite catalyst for the decontamination reactions of O, S-diethyl methyl phosphonothiolate

The decontamination reactions of O,S-diethyl methyl phosphonothiolate, as an agricultural organophosphorous pesticide onto 20 wt% loaded manganese dioxide nanoparticles-silver-Y zeolite as a nanocomposite catalyst in different solvents, were evaluated and monitored by means of gas chromatography-flame ionization detector and gas chromatography-mass spectrometry. Prior to the reaction, the catalyst was synthesized in three steps: at first, sodium-Y zeolite was prepared by hydrothermal method; then, silver-Y zeolite was prepared from sodium-Y zeolite using ion exchange procedure; and finally, manganese dioxide nanoparticles were synthesized by in situ impregnation method by pouring the pre-prepared silver-Y zeolite into manganese(II) nitrate solution and loaded as 20 wt% onto silver-Y zeolite structure. The formation of the synthesized units and final nanocomposite catalyst was verified through scanning electron microscopy, X-ray diffraction, atomic absorption spectrometry and Fourier transform-infrared spectroscopy techniques. Gas chromatography chromatograms showed that O,S-diethyl methyl phosphonothiolate was decontaminated perfectly by the catalyst in n-heptane solvent after 8 h, at room temperature, while chloroform and isopropanol solvents and other reaction times gave lower decontamination results. Moreover, gas chromatography-mass spectrometry chromatograms confirmed the formation of ethyl methyl phosphonic acid as a major and final product, which exemplifies the role of hydrolysis reaction during the degradation progress.