The Innovation Team of Soil Health Care of the Institute of Agricultural Resources and Regional Planning (IARRP) of the Chinese Academy of Agricultural Sciences (CAAS) has made significant progress in the immobilization of cadmium (Cd) in alkaline soil. Their findings, titled "The immobilization of cadmium by rape straw derived biochar in alkaline conditions: Sorption isotherm, molecular binding mechanism, and in-situ remediation of Cd-contaminated soil," have been published in "Environmental Pollution" (IF = 8.9).

The issue of Cd contamination in alkaline soils in the North China Plain and its impact on agricultural product safety has been increasingly recognized, necessitating the development of effective immobilization materials and techniques. Biochar has garnered attention due to its potential for immobilizing heavy metals, with several studies emphasizing its effectiveness in immobilizing heavy metals in acidic contaminated soils and water. However, the applicability of biochar as a remediation material for immobilizing Cd under alkaline conditions and its microscopic interaction mechanism with Cd remain unclear.

In this study, rapeseed straw was selected as the raw material, and biochar (RB400 and RB700) was prepared through pyrolysis at 400°C and 700°C, respectively. The immobilization effect and mechanism of rapeseed straw biochar at different pyrolysis temperatures under alkaline conditions were evaluated through adsorption experiments and soil incubation experiments. X-ray absorption near-edge structure (XANES) spectroscopy analysis confirmed differences in the molecular binding forms of Cd in RB400 and RB700. In RB400, Cd mainly existed in an organic-bound form in the adsorption products, while in RB700, Cd primarily existed as cadmium carbonate. Solid-state ¹³C nuclear magnetic resonance spectroscopy (¹³C-NMR) analysis indicated that aromatic and carboxyl carbon functional groups on the char surface participated in the organic adsorption of Cd under alkaline conditions through chelation and Cd²⁺-π coordination. Compared to RB400, RB700 exhibited a stronger immobilization effect on alkaline soil Cd, leading to a significant 15.54% reduction in the DTPA-extractable Cd content in the soil. These results highlight the immobilization effect of rapeseed straw biochar on Cd in alkaline contaminated soil, providing theoretical support for the immobilization and fixation technology of Cd in alkaline Cd-contaminated soil.

Researcher Yang Jianjun from the IARRP is the corresponding author of the paper. This research was supported by the National High-level Talents Special Support Plan for Young Top-notch Talents, the National Modern Agricultural Industry Technology System Special Fund (CARS-03), and the Chinese Academy of Agricultural Sciences Agricultural Science and Technology Innovation Program (2021-2025).

Citation: Yang J, et al. The immobilization of cadmium by rape straw derived biochar in alkaline conditions: Sorption isotherm, molecular binding mechanism, and in-situ remediation of Cd-contaminated soil. Environmental Pollution, 2024, 123969.

Paper link: https://doi.org/10.1016/j.envpol.2024.123969