Evaluating biochar impact on topramezone adsorption behavior on soil under no-tillage and rotary tillage treatments: Isotherms and kinetics

Abstract

The evaluation of biochar application on the adsorption behavior of topramezone on soil under no-tillage (NT) and rotary tillage treatments (RT) has been assessed. Fourier Transform InfraRed Spectrometry (FTIR), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller) (BET) were used for the biochar characterization. Batch experiments were carried out in a laboratory to assess the adsorption of topramezone on soil through equilibrium and kinetic modeling under biochar addition. The clay content has been found to be higher under NT (18.24 ± 0.01) than under RT (15.91 ± 0.02). The total organic carbon was higher under NT. The topramezone adsorption equilibrium reached after 8 and 12 h, for NT and RT, respectively. The kinetic and thermodynamic analyses showed the adsorption under both treatments matched with pseudo-second-order kinetic and Langmuir models, respectively. After biochar addition, the pesticide adsorption capacity (40 < 25 < 15 °C) increased with decreasing temperature suggesting an exothermic adsorption process while negative values of Gibbs free energy (ΔG); −1848.07 and −366.531 J mol−1; for the soil under NT and RT at 25 °C, respectively, indicated spontaneous adsorption. Negative entropy values (ΔS); −21.92 and −78.296 J mol−1K−1, for NT and RT, respectively, explained a decreased randomness process. The enthalpy was higher (p < 0.05) under RT (−23,274.6 J mol−1) than under NT (−1313.73 J mol−1). Conclusively, it was shown that the topramezone adsorption capacity was higher under NT, and biochar addition increased more pesticide adsorption under NT than under RT.