蛇纹石基重金属钝化剂构筑及其对土壤镉钝化修复

In the past few years, the heavy metal pollution in soil environment has been more serious and become an important issue in agricultural production safety and people healthy. Among the numerous treating measures for heavy metal contaminated soil, in-situ passivation has received widespread attention due to its simplicity, efficiency and unchanged the use of land. In this project, the thermal activated serpentine with different structure is modified by mercapto or amino group using surface grafting method to obtain serpentine-based passivator, which is used to immobilize cadmium in soil. Its ability of immobilization heavy metal in soil is improved by reasonable regulating the structure and the mercapto or amino group content of serpentine. The structure and surface groups of the modified serpentine are characterized by XRD, FT-IR, XPS, and SEM. The effect of preparation condition on unsaturation Si-O-Si, O-Si-O, magnesium bond, hydroxyl, mercapto and amino group of serpentine surface and structure of serpentine is determined. Meanwhile, the mechanism for the effect of the structure, surface group and synergy on cadmium adsorption and transformation of cadmium formations is investigated by virtue of laboratory simulation experiments and pot experiments. The achievement of the project will lay a foundation for passivation remediation of cadmium contaminated soil.

近年来我国土壤重金属污染形势日趋严峻，已成为影响农产品质量安全和人们身体健康的重要问题。在众多重金属污染土壤治理方法中，原位钝化修复因其简单、快捷、不改变土地用途，受到广泛关注。本项目以不同结构热活化蛇纹石为基体，采用表面接枝方法对其进行巯基或氨基修饰。通过合理调控蛇纹石结构与接枝的巯基或氨基量，提高其钝化土壤中重金属能力，进而构筑高性能重金属钝化剂，并用于修复镉污染土壤。通过XRD、FT-IR、XPS、SEM等技术，对改性蛇纹石的结构及表面官能团进行表征，探明制备条件对蛇纹石结构和不饱和Si-O-Si、O-Si-O、含镁键类、羟基、巯基或氨基等官能团的影响规律，并借助实验室模拟实验和盆栽实验，阐明蛇纹石基钝化剂结构、表面官能团及相互作用等因素对镉的吸附和改变土壤镉赋存形态的作用机制，以期为镉污染土壤钝化修复提供理论依据和技术支撑。

随着工农业的快速发展，土壤重金属污染越发严重，已成为影响农产品质量安全和人们身体健康的重要问题。因此，重金属污染土壤修复引起了广泛关注。在众多重金属污染土壤治理方法中，原位钝化修复因其简单、快捷、不改变土地用途，成为研究的热点。本项目以储量丰富的天然蛇纹石为原料，对其在不同温度下进行热活化处理，得到具有不同结构的热活化蛇纹石，然后以其为基体，采用表面接枝方法对其进行巯基或氨基修饰。通过调控热活化温度可以调变蛇纹石的结构及表面羟基的量，进而可以调控表面接枝的巯基或氨基量，制备具有结构可控，表面官能团可调的蛇纹石基重金属钝化剂，并用于修复镉污染土壤。结合XRD、FT-IR、XPS、SEM等表征技术和实验室模拟实验，发现热活化过程中，蛇纹石发生了脱羟基反应，Mg-OH和Si-O键断裂，且随着活化温度的升高，Si、Mg含量增加，蛇纹石的层状结构不断遭到破坏，表面积逐渐增加。热活化蛇纹石表面羟基的量决定了嫁接的巯基或氨基量。蛇纹石中MgO水解导致溶液体系pH升高，因此，蛇纹石经过热活化和巯基、氨基改性后，由于表面积、MgO含量的增加以及表面巯基、氨基官能团的引入，使得重金属镉以碳酸镉、氢氧化镉沉淀以及与氨基或巯基络合等形式存在蛇纹石表面。土培及盆栽实验进一步表明，施加改性蛇纹石后，通过表面吸附、表面沉淀及络合等作用，促使土壤中镉由生物活性较高的可交换态向生物活性较低的铁锰氧化物结合态和残渣态转变，使得水稻糙米中镉含量显著降低。在700℃热活化然后接枝氨基官能团的蛇纹石钝化剂表现出较好的重金属镉钝化效果。