Gamma-ray treatment in the presence of ozone (O3) and titanium dioxide (TiO2) showed an efficient removal of trichloroethylene (TCE) and perchloroethylene (PCE). Without gamma-irradiation, TCE and PCE were not sufficiently decomposed to comply with the water quality limit of groundwater. However, near 100% of TCE and PCE were removed at a dose of 300 Gy in the presence of O3 and TiO2, where TiO2 showed an explicit enhancement of decomposition. Cytotoxicity test using Chinese hamster V79 cells showed no toxicity of the TCE and PCE decomposition products.
Carbonate ions significantly inhibit the decomposition of TCE (trichloroethylene) and PCE (perchloroethylene) by gamma-rays. The inhibition effect is larger in the case of TCE than PCE due to a greater dependence of TCE decomposition on hydroxyl radicals. The inhibition effect of carbonate ions was characterized by an EPR/spin-trapping technique. The intensity of DMPO-OH adduct signal decreased as the carbonate ion concentration increased and the percent of signal reduction was linearly proportional to the logarithm of carbonate ion concentration. This directly proves that the carbonate ions inhibit the decomposition of TCE and PCE by scavenging hydroxyl radicals.
Radiation treatment in the presence of catalysts such as anatase, P25 and bentonite showed efficient removal of TCE (trichloroethylene) and PCE (perchloroethylene) compared with gamma-irradiation alone. Gamma-ray pretreatment of P25 and bentonite enhanced the decomposition of TCE and PCE, respectively. The change in the catalysts by gamma-rays was characterized by their EPR spectra. For anatase and bentonite, the peaks in the spectra increased significantly, and the pattern of the spectra changed in the case of P25. The relationship between the peaks and pollutant decomposition should be further clarified due to the complexity of the spectra.
Stable and transient products of the -radiolysis of dichloromethane (DCM) and 1,1-dichloroethane (11 DCE) have been investigated in an oxygen-free atmosphere. The stable products were separated by preparative gas chromatography and identified by NMR and mass spectroscopy. The quantitative determinations were performed by potentiometric and gas chromatographic analysis. The main products of radiolysis of DCM are dimers (11DCE, 12DCE, 112TCE, 1122TetraCE) and the product of dechlorination CM; in the case of 11DCE-dimers (133TCB, 2233TetraCB) and the product of dechlorination CE as well as products of isomerization and chlorination of the parent compound (12DCE, 112TCE). The gas products of both chlorides are HCl and H2. The ESR investigations at 77 K indicate the formation of at least two kinds of radicals in both chlorides: CH2Cl/CHCl2=1/3 in DCM and CH3CCl2/CH3CHCl=2.5/1 in 11DCE. An outline of the mechanism of radiolysis is proposed.
Authors:L. Cavallo, J. Ducéré, Rosalisa Fedele, A. Melchior, Maria Mimmi, G. Morini, F. Piemontesi, and Marilena Tolazzi
A calorimetric investigation on the reactions of TiCl4 with phthalates in 1,1,2,2-tetrachloroethane (TCE) is presented in order to better understand the complex interactions present
in Ziegler-Natta catalytic systems. The Lewis bases diethyl isophthalate (L1), diethyl terephthalate (L2) and the ortho-isomer diethylphthalate (L3), have been chosen to study how the substituent positions could influence the energy and the stoichiometry of the complexation
FTIR spectroscopy was used to obtain information on the coordination mode of the ligands and diffusion measurements by NMR
was carried out to verify the presence of oligo-or polymeric species. Experimental results were compared with theoretical
calculations based on Density Functional Theory (DFT).
. Advances in Water Resources. 29. 227–238.
Dane, J. H., Oostrom, M. & Missildine, B. C., 1992. An improved method for the determination of capillary pressure-saturation curves involving TCE, water, and air. Journal of Contaminant