巯基改性蒙脱石对中国北方中碱性农田土壤镉钝化效果研究

农田土壤重金属污染是影响中国农产品环境质量安全的主要因素。钝化材料是修复农田重金属污染土壤的关键材料，研究开发出高效土壤重金属钝化材料，对于修复重金属污染农田和保障农产品食用安全非常重要。本文以蒙脱石为原材料，将巯基基团负载在其表面或层间制备巯基改性蒙脱石，借助X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)和傅里叶红外光谱(FTIR)等技术表征巯基改性蒙脱石的特性，并开展室内土培试验，采用二乙三胺五乙酸浸提-火焰原子吸收分光光度法分析土壤镉的有效态，通过Tessier修正顺序七步提取法分析土壤镉的赋存形态。结果表明：蒙脱石经巯基改性后不仅新增了C−H、S−H共价键，而且增强了−OH和C=O化学键的活性，能与Cd2+发生巯基及羟基配位吸附。供试土壤添加巯基改性蒙脱石后，由于巯基配位吸附作用使土壤离子交换态镉转化为铁锰氧化物结合态，而增强的羟基配位吸附作用使其转化为碳酸盐结合态，结果使土壤中镉的赋存形态发生显著改变，离子交换态大幅减少，作物根系可吸收的土壤有效镉显著降低。添加1%、3%、5%巯基改性蒙脱石后，土壤有效镉分别降低21.92%、69.11%、82.90%；而作为对照组添加1%、3%、5%蒙脱石仅分别降低3.37%、1.80%、6.71%。蒙脱石经巯基改性后对土壤镉的钝化效果得到显著提升，土壤有效镉的降低幅度有随巯基改性蒙脱石添加量增加而提高的趋势。巯基改性蒙脱石对中国北方中碱性农田土壤镉的钝化效果显著，具有一定的参考应用价值。

Passivation Effect of Thiol-Modified Montmorillonite on Cadmium in Medium-Alkaline Farmland Soil in Northern China

Passivation material is a key material for repairing heavy metal contaminated soil in farmland. To study and develop efficient soil heavy metal passivator, thiol-modified montmorillonite was studied. Montmorillonite was used as the raw material, and the thiol group was loaded on the surface or interlayer of montmorillonite to prepare thiol-modified montmorillonite. The characteristics of thiol-modified montmorillonite were characterized by XRD, SEM, TEM and FTIR, and the indoor soil culture test was carried out. The thiol-modified montmorillonite not only added C-H and S-H covalent bonds, but also enhanced the activity of -OH and C=O chemical bonds, and could adsorb with Cd2+ by thiol and hydroxyl coordination. As a result, the occurrence form of Cd in the soil was significantly changed, the ion exchange state was greatly reduced, and the available Cd in the soil absorbed by the crop roots was significantly reduced. After adding 1%, 3% and 5% thiol-modified montmorillonite, the available Cd in soil decreased by 21.92%, 69.11% and 82.90%, respectively. The passivation effect of montmorillonite on soil Cd was significantly improved after thiol modification, and the decrease of available Cd in soil tended to increase with the increase of thiol-modified montmorillonite. The BRIEF REPORT is available for this paper at http://www.ykcs.ac.cn/en/article/doi/10.15898/j.ykcs.202309010147.