Effects of biochar underwent different aging processes on soil properties and Cd passivation

This study aims to determine the efficacy of biochar underwent different aging process including freeze-thaw cycling aging (FB), acidified aging (AB), and microbial aging (MB) on soil physicochemical properties and Cd passivation. The Cd-contaminated soil (3 mg·kg−1) amended with the three kinds of aging biochar (at 4% w:w) were subjected to 56-day incubation. The application of FB and MB in soil increased the soil pH (0.82–1.04, 0.27–9.36), CEC (1.06–2.53 cmol·kg−1, 1.66–2.59 cmol·kg−1), and organic matter content (2.28–4.67 g·kg−1, 3.70–5.48 g·kg−1). FB performed best in stabilizing Cd (17.06–23.65%). On the contrary, AB decreased the soil pH and CEC by 0.82–1.04 and 1.32–2.40 cmol·kg−1 and activated Cd by 11.6–19.24%. In conclusion, the efficacy of biochar on soil remediation and Cd passivation varied with aging method and cycle, and freeze-thaw treatment is an effective approach to improve the performance of biochar.