| Summary: | 博士 === 國立成功大學 === 環境工程學系 === 89 === Abstract
The main objective of this work was to investigate the mineralization of chlorine-containing wastes (such as CCl4) with copper species. Specifically, we examined the speciation of copper during the mineralization of CCl4 by X-ray based spectroscopic methods such as X-ray diffraction (XRD), XANES, EXAFS and X-ray photoelectron spectroscopy (XPS) and revealed the possible reaction pathway in the mineralization process. In addition, photocatalytic decomposition of CCl4 in H2O effected by Zr-MCM-41, oxidation of Br-containing organic wastes in supercritical water and an exploratory study of synthesis of diamond materials in supercritical water have also been conducted in the present work.
Experimentally, CCl4 was effectively mineralized by CuO to yield stable inorganic species of CO2 and CuCl2 (CCl4 + 2CuO → 2CuCl2 + CO2). High CCl4 conversions (63-83%) were found in the mineralization process performed at 513-603 K for 10-30 minutes. Speciation of copper in the mineralization product solid was also studied by extended X ray absorption fine structure (EXAFS) spectroscopy. Bond distances of Cu-O and Cu-Cl in the CCl4-mineralized product solid were 1.93-1.94 and 2.10-2.12 Å, respectively, which were greater than those of normal CuO and CuCl2 by 0.03-0.07 Å. The increase of the bond distances for Cu-O and Cu-Cl might be due to Cl insertion and concomitantly structural perturbation of unreacted CuO in the mineralization process. For the second shell around copper atom, bond distances of Cu-(O)-Cu also increased by 0.03-0.05 Å and the coordination numbers of Cu-O and Cu-(O)-Cu decreased, as expected, in the mineralization process. Chloride atoms might be further captured by CuO, yielding CuCl2 in the mineralization process.
Photocatalytic decomposition of CCl4 on Zr-MCM-41 generated mainly CHCl3, Cl- and H2. Little C2Cl4, C2Cl6 or CH2Cl2 was observed. By justifying the band gaps between the conduction band (CB) and the valance band (VB) of ZrO2, the photocatalytic decomposition of CCl4 on Zr-MCM-41 was enhanced by at least 1.97, compared to that on ZrO2. In addition, Zr-MCM-41 also enhanced the photocatalytic decomposition of H2O. The H2 yield was 6.5 mmolhr-1(gZrO2)-1.
Oxidation of Br-containing wastes with NaOH in supercritical water has been investigated. Experimentally, Br species in the Br-containing wastes was abstracted by sodium cations and the destruction efficiency of the waste was enhanced in the supercritical water oxidation (SCWO) process. By means of X-ray diffraction (XRD) spectroscopy, Cu2O, CuO, and Cu(OH)2 were found in solid residue of the SCWO of the Br-containing wastes. The EXAFS spectra indicated that the bond distance of Cu-O in the residue was 1.87 Å with a coordination number of 2.61.
An exploratory study for synthesis of diamond materials in supercritical water has also been conducted. Possible existence of diamond materials was found in the decomposition of CCl4 in the presence of cations such as Na+ in supercritical water at >753 K and >250 atm.
Key words: CCl4, Mineralization, Photodecomposition, Supercritical water, Diamond
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