Mechanistic Study of Thermally Immobilized Cr- or Cu-containing SiO2

• Main Authors: CHIU SHU-YUAN, 邱淑媛
• Other Authors: WEI YU-LING
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/46234999715445772204

碩士 === 東海大學 === 環境科學系 === 89 === X-ray absorption spectroscope (XAS), X-ray diffraction (XRD), scanning electron microscope/energy dispersive spectrometer (SEM/EDS), and the toxicity characteristic leaching procedure (TCLP) technique, were used to study the effect of surface area (SL: 2 and SH: 378 m2/g) of SiO2 on the thermal immobilization of 0.6295 mole chromium in 1.0 kg Cr(Ⅵ)-sorbed SiO2 or 0.6295 mole copper in 1.0 kg Cu(Ⅱ)-sorbed SiO2 that had been heated at 105 for 3-5days, or 500, 700, 900, or 1100 ℃ for 2 hours. Our data indicate the followings. In the Cr(Ⅵ)-sorbed aspects, the Cr(Ⅵ)-sorbed SL thermally treated at 500-1100 ℃ always leached less Cr than the SH. In the contrast, opposite results were observed for the samples heated at 105 ℃. Cr-concentrated region was formed, as detected with SEM/EDS technique, on Cr(Ⅵ)-sorbed SL after the thermal treatment at 500-1100 ℃, but not formed on the corresponding SH. The sorption of Cr(Ⅵ) onto both SH and SL could retard the thermal reduction of Cr(Ⅵ) at 500-1100 ℃ as evidenced by the extent of variation of pre-edge intensity of XAS spectra. The extent of retardation of Cr(Ⅵ) reduction to Cr2O3 increased with the amount of Cr(Ⅵ) sorption on unit mass of SiO2. In the Cu(Ⅱ)-sorbed aspects, the Cu(Ⅱ)-sorbed SL thermally treated at 500-1100 ℃ always leached less Cu(Ⅱ) than the SH. In the contrast, opposite results were observed for the samples heated at 105 ℃. Cu-concentrated region was formed, as detected with SEM/EDS technique, on Cu(Ⅱ)-sorbed SL (500-1100 ℃)and SH (500-900 ℃). The main species of Cu(Ⅱ)-sorbed SL is Cu(OH)2 for the samples heated at 105 ℃. After the thermal treatment at 500-1100 ℃, the Cu(OH)2 species of was transformed to CuO.