Synthesis and Characterization of MgO Nanoparticles by Modified Sonochemical Method and their Catalytic Studies against Organophosphates and Pesticides

Abstract

In the present work, magnesium oxide nanoparticles were synthesized successful-ly by sonochemical, microwave assisted sonochemical, sonochemical followed by boiling and simple wet chemical methods. Magnesium nitrate hexahydrate [Mg(NO3)2.6H2O] and NaOH were used as the precursor materials with distilled water as a solvent. Polyvinyl pyrollidone (PVP), polyvinyl alcohol (PVA) and methylcellulose were used as structure directors to prevent agglomeration and control morphology of nanoparticles and also to study the effect of different stabilizers on the size of nanoparticles. Different concentra-tions of precursors were used to check their effect on size and morphology of particles. The Mg(OH)2 nanoparticles obtained from this method were calcined at 500 oC in order to get MgO nanoparticles. All the samples were characterized by Fourier transform infrared spectroscopy (FTIR), UV- visible spectroscopy, X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), BET and TGA-DTA. Results showed that particle size and surface area of MgO nanoparticles were pH sensitive. The XRD spectra indicated that the synthesized nanocrystalline MgO has a cubic structure. SEM images were accorded with the AFM and XRD data showing that the average sizes of the particles were in the range of nanometer. Catalytic activities of MgO nanoparticles were studied in the current research work against organophosphate compounds i.e. hexamethyl phosphoramide (HMPA) and omethoate. Degradation products were studied by GC/MS. Photocatalytic activity of MgO nanoparticles and MgO nanoparticles + Bulk ZnO of E. Merck were also studied. Results showed that nanocrys-talline MgO is an efficient decontamination agent against organophosphorous compounds particularly HMPA and omethoate. Dichloromethane (DCM) and isopropyl- alcohol (IPA) were used as extraction solvents but DCM was found best solvent for extraction of degradation products both for HMPA and omethoate. GC/MS data confirmed that both HMPA and omethoate can be degraded into their non toxic compounds at room temperature as well as in the presence of sunlight. The degradation efficiency of nanocrystalline MgO increases by increasing the exposure time of organophosphate compounds to nanoctalyst i.e. MgO nanoparticles.