(1. School of Rail Transportation, Soochow University, Suzhou, Jiangsu 215131, China; 2. Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering, Hohai University, Nanjing, Jiangsu 210098, China; 3. Jiangsu Research Center for Geotechnical Engineering Technology, Hohai University, Nanjing, Jiangsu 210098, China; 4. College of Economics and Management, Changshu Institute of Technology, Changshu, Jiangsu 215500, China; 5. Suzhou Tonghe Environmental Engineering Co., Ltd., Suzhou, Jiangsu 215011, China)
Abstract： Iron powder was used as passivator to analyze the adsorption characteristics of iron powder for Cd(Ⅱ) under various key factors through adsorption experiment. The process of Cd(Ⅱ) adsorption by iron powder was investigated through adsorption isotherm and adsorption kinetic models. By scanning electron microscope (SEM) photographs and Xray diffraction (XRD) spectra, the adsorption mechanism was explored. The experimental results show that unit adsorption amount of iron powder is increased with the increasing of initial solution concentration level and reaction time and is decreased with the increasing of dosage. The initial solution pH has little effect on Cd(Ⅱ) adsorption by iron powder. When the initial solution concentration is 100 mg·L-1 with dosage of 20 g·L-1 and reaction time of 48 h, the removal efficiency of Cd(Ⅱ) is 94% with equilibrium adsorption capacity of 4.69 mg·g-1. Langmuir isotherm, Freundlich isotherm, RP isotherm and intraparticle diffusion model are consistent with the adsorption process. Mechanism discussion shows that the removal of Cd(Ⅱ) is mostly pushed by the combination of physical adsorption and chemical adsorption by iron powder, while the chemical adsorption is dominant. The specific means include reduction of Cd(Ⅱ) by iron powder, coprecipitation of ironcontaining colloid with Cd(Ⅱ) and electrostatic interaction.
