Efficiency of CH4N2S−modified biochar derived from potato peel on the adsorption and fractionation of cadmium, zinc and copper in contaminated acidic soil

Abstract

The objective of this study was to investigate the characteristics of potato peel biochar (PPB) and modified potato peel biochar (MPPB), and their effects on the adsorption and fractionation of some heavy metals in contaminated acidic soil. The results showed that the modified potato peel biochar has a higher pH, cation exchange capacity (CEC), surface functional groups, oxygen/carbon (O/C), and hydrogen/carbon (H/C) ratios than the PPB. The addition of modified biochar to soil, especially at the application rate of 8 %, increased soil pH, CEC, and organic carbon (OC). The maximum adsorption capacity values of Cd, Zn, and Cu in the soil amended with MPPB at the application rate of 8 % were 5142.63, 3508.44, and 4993.12 mg kg−1, respectively. The addition of MPPB to the soil transformed the unstable fraction (soluble and exchangeable) of heavy metals to stable fractions (Fe/Mn oxides–bound, organically–bound, and residual). Compared to the control treatment, the soluble and exchangeable fraction of Cd, Zn, and Cu in soil amended with 8 % MPPB decreased to 102.97, 94.4, and 76.18 mg kg−1, respectively. The order of increment of organically–bound and residual fractions of heavy metals in soil amended with 8 % MPPB were Cu > Cd > Zn and Cd > Cu > Zn, respectively. The results of this study showed that MPPB can be used as a low-cost and eco-friendly adsorbent for the immobilization of heavy metals in contaminated acidic soils.