Effects of corn stalks Biochar Amendment and Freezing-Thawing on the Cd Adsorption of Saline-Alkali Soil

The main objective of this work was to study the adsorption characteristics of Cd by adding corn stover biochar and saline-alkali soil after freezing and thawing, and the saline-alkali land in Lesheng Town, Da'an City, Jilin Province was selected as the model/representative area. The artificially simulated freezing and thawing environments was conducted in the experiments. After the soil is incubated, adsorption experiments were carried out. FTIR spectra analysis indicated that biochar amendment increased the aromatic contents of the soil. Moreover, the results showed that regardless of biochar amendment, the freezing-thawing could increase hydroxyl, carboxyl, and aromatic hydrocarbon contents. In contrast, freezing-thawing reduced the soil pH, cation exchange capacity, conductivity, and exchangeable sodium (regardless of biochar amendment). In all cases, Cd adsorption isotherms and kinetic curves were best fit by the Langmuir equation and quasi-second-order kinetic equation, respectively, and the thermodynamic parameters of Cd adsorption (ΔG < 0, ΔH > 0, and ΔS > 0) suggested that the process was consistently spontaneous, endothermic, and disordered. A significant increase in soil Cd adsorption capacity was observed in the with increasing pH.