Effect of Sludge Biochars Obtained at Different Pyrolysis Temperatures on the Adsorption of Cd(II)by Loess in Northwestern China.

The effect of sludge biochars obtained at different temperatures on the adsorption of Cd(II) by loess in northwestern China was investigated using the batch equilibrium method. The results showed that the pseudo second-order kinetic model can describe the kinetics of Cd(II) adsorption on the sludge biocharamended loess very well. The adsorption of Cd(II) by loess reached equilibrium in 6h. However, with the addition of biochar, the adsorption time of the Cd(II) by loess decreased. In addition, the adsorption equilibrium time decreased significantly with increasing pyrolysis temperatures. When the pH increased from 2 to 7, the adsorption capacity of biochar-amended loess increased, while the adsorption capacity was in equilibrium or even slightly decreased in the pH range from 7 to 8. The Langmuir model can describe the adsorption isothermal behaviours of Cd(II) by biochar-amended loess. The adsorption capacity of biochar-amended loess samples for Cd(II) at 25°C follows the order of LSB700 (28.74 mg/g)>LSB500 (22.42 mg/g)>LSB300 (17.67 mg/g). The addition of sludge biochars can significantly improve the saturation adsorption capacity of loess for Cd(II). Therefore, the addition of sludge biochars can effectively improve the adsorption-immobilization capability of loess for Cd(II). [ABSTRACT FROM AUTHOR]