| The modified clay coated with iron oxides was prepared in this study. The influences of the dose of clay, temperature, and the molar rate of Fe3+and OH- on the preparation were investigated. Then the adsorptive capacity of the modified clay and raw clay were compared. The experimental results show that the adsorption capacity of clay to metals can be enhanced greatly by modified with iron oxides.The prepared modified clay was used for the removal of Cr(VI),Cd2+ and Ni2+ from aqueous solution. The effects of contact time, pH, ion concentration and temperature on the adsorption by modified clay were investigated. The results indicated that the high adsorption capacity for Cr(VI) can be achieved in 3 h of equilibration time. The adsorption of Cr(VI) by modified clay increased with increasing of initial concentration of Cr(VI)and temperature, but decreased significantly with increasing of pH. The effects of factors on the adsorption for Cd2+ and Ni2+ by modified clay showed similar trend. Both the equilibration time of Cd2+ and Ni2+ were 40 min. The adsorption of Cd2+ and Ni2+ by modified clay increased with increasing of pH, ion concentration and temperature.At an optimum pH of 3.0, the adsorption kinetics and isotherms of Cr(VI) can be best fitted with the second order rate kinetics model and Langmuir model respectively. The maximum adsorption capacity of modified clay calculated by Langmuir model was found to be 12.91 mg.g-1 in 293 K. The thermodynamic parameters revealed that the adsorption of Cr(VI) by modified clay was a spontaneous and endothermic process. Meanwhile, the adsorption kinetics and thermodynamic of Cd2+ and Ni2+ were researched in this study. The dynamics process can be used the second order kinetic equations to descript. The thermodynamic parameters show that both the adsorption of Cd2+ and Ni2+ by modified clay all were spontaneous and endothermic process.
|
PDF Full Text Request