Electrokinetic Treatments of Copper/Zincin Contaminated Soils and Wastes

• Main Authors: Ming-Yan Yu, 余明彥
• Other Authors: H. Paul Wang
• Format: Others
• Language: en_US
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/30124603786925092993

碩士 === 國立成功大學 === 環境工程學系碩博士班 === 92 === 　　Electrokinetic remediation (EKR) is a promising method with advantages in in-situ treatments of contaminated soils. EKR may be applicable in low hydraulic permeability and fine granted soils. The main objective of this work was to study the electrokinetic treatments of copper- and lead-contaminated soils, chemical mechanical planarization (CMP) waste water, and phosphor wastes. Experimentally, enhanced dissolution of copper and lead in a contaminated soil under electric field (0-5 volts/cm) in the presence of 40% of H3PO4 and/or 2% of H2O2 was conducted. In addition, H+ generated from photocatalytic degradation of water was used to accelerate the dissolution of copper from soils. Copper in the CMP waste water was effectively trapped in the shape selective molecular sieves (MCM-41 (40 Å) or Zeolite Y (7.4 Å)) under electric field. Selective toxic metals in phosphor wastes during thermal and electrokinetic treatments were also studied in the present work. 　　X-ray absorption near edge structural spectra (XANES) showed that most of CuCl2 and about 28% of CuCO3 were dissolved into the aqueous phase as Cu2+ in the presence of H3PO4 (40%). After 90 minutes of EKR, at least 26% of Cu(II) were transported toward the cathode by electric field. In the EKR process, the axial Cu-O-Cu bond distance in the soils was increased by 0.34 Å and coordination numbers were decreased by 1.1, which might be due to the outer-sphere copper was distorted or dissolved into the electrolyte. Similarly, in the presence of H3PO4 (40%) and H2O2 (2%), most of CuCl2 and about 23% of CuCO3 were dissolved into the aqueous phase. During EKR, at least 91% of Cu(II) were transported toward the cathode. The axial Cu-O-Cu bond distance in the soils was increased by 0.68 Å and coordination numbers were decreased by 2.5. 　　Extraction of copper from the contaminated soil with acid (HNO3, H3PO4, C2H2O4, or CH3COOH) was compared with H+ generated from photocatalytic degradation of water. About 0.5-0.7 mg/L of Cu(II) were extracted from soils with the H+ yielded from photocatalytic degradation of water on Zr-Ti-SiO2, nano-TiO2, and Ti-MCM-41 photocatalysts for six hours. 　　During the thermal treatments for eight hours at 673-1273 K, 36% of ZnS in the phosphor wastes might be oxidized to ZnO in the presence of air. It turns out that electrokinetic might be more effective than the thermal treatments in recovery of Zn from the phosphor wastes by at least 12%.