monocrotophos and titanium-dioxide

Mg-doped TiO(2) with different Mg concentrations were prepared using sol-gel method and characterized by XRD, UV-visible, XPS, SEM and FT-IR. The XRD results revealed that Mg(2+) goes into the TiO(2) lattice. SEM images of the doped and pure TiO(2) indicated that there is a smaller particle size for the doped catalyst compared to that of the pure TiO(2). UV-visible absorption spectra indicated that upon doping with Mg(2+) ion, the catalyst exhibits absorption in visible region. FT-IR and XPS spectra demonstrated that the presence of Mg(2+) ion in the TiO(2) lattice as substitutional dopant. Photocatalytic activity of doped TiO(2) has been evaluated by degradation of the monocrotophos (MCP) pesticide. The effect of solution pH, catalyst dosage and initial concentration of MCP on the photocatalytic activity of Mg-doped TiO(2) with different loadings was studied. It was observed that the rate of degradation of MCP over Mg-doped TiO(2) is better than Pure TiO(2) and Degussa P-25.

Topics: Catalysis; Endocrine Disruptors; Hydrogen-Ion Concentration; Insecticides; Magnesium; Microscopy, Electron, Scanning; Monocrotophos; Photochemistry; Spectrophotometry, Ultraviolet; Spectroscopy, Fourier Transform Infrared; Titanium; X-Ray Diffraction

Monocrotophos (MCP) is an organophosphate insecticide that has been found as a pollutant in aqueous environments. The sonolytic, photocatalytic and sonophotocatalytic degradation of MCP in the presence of homogeneous (Fe(3+)) and heterogeneous photocatalysts (TiO(2)) were studied. The photocatalytic degradation rate using TiO(2) was found to be lower than that of sonolysis alone due to the interference of phosphate ions formed as an intermediate product. On the other hand, a 15 fold enhancement in the degradation rate was found when photolysis was carried out in the presence of Fe(3+) compared to the rate observed with photolysis alone. The combination of sonolysis and photocatalysis (using either TiO(2) or Fe(3+)) showed a detrimental effect. Synergy indices of 0.62 and 0.87 were found for the sonophotocatalytic degradation of MCP in the presence of TiO(2) and Fe(3+), respectively. Total organic carbon (TOC) analysis was carried out to study the extent of mineralization of MCP. It was found that the mineralization process was additive for both TiO(2) and Fe(3+) sonophotocatalysis. HPLC and electrospray mass spectrometry (ESMS) techniques were employed for the identification of the degradation intermediates. The sonication of MCP led to the formation of dimethyl phosphate, dimethylphosphonate, 3-hydroxy 2-buteneamide and N-methyl 3-oxobutanamide as the intermediate products.

Topics: Catalysis; Ferrous Compounds; Insecticides; Monocrotophos; Photolysis; Sonication; Titanium; Water Pollutants, Chemical; Water Purification

The decomposition of monocrotophos in aqueous solution by UV/TiO2 reduction process was studied under various pH values, TiO2 dosages, light intensities, dissolved oxygen levels and other operating conditions. The presence of dissolved oxygen inhibits the recombination of electrons and holes, and enhance the decomposition of monocrotophos by UV/TiO2 process, but excessive dissolved oxygen posed no further effect on the decomposition of monocrotophos. The decomposition rates of monocrotophos were significantly higher for acidic solutions than those for alkaline solutions. Increasing the light intensity would drastically increase the decomposition rate of monocrotophos, but was ultimately influenced by the amount of TiO2 present in solutions. The quasi-global kinetics based on a simplified consecutive reaction scheme was developed to describe the temporal behavior of monocrotophos decomposition in aqueous solution by UV/TiO2 process.

Topics: Animals; Female; Hydrogen-Ion Concentration; Insecticides; Mice; Monocrotophos; Pregnancy; Solutions; Titanium; Ultraviolet Rays