具有重金属离子选择反应性的纳米二氧化硅结构设计、制备及其对污染土壤的钝化修复行为研究

The pollution of soil by heavy metals is one of the major environmental issues to be solved in our country, and the chemical immobilization of heavy metals is a significant pathway to remediate the contaminated soil. With a view to major pollutants including lead, arsenic, chromium, mercury, and cadmium, this project aims at designing and preparing highly active organic-inorganic hybrid materials which are capable of immobilizing heavy metals. Using nanoscale silica possessing good compatibility with soil as the carrier and organic compounds (containing functional groups such as sulfhydryl, dithiocarboxyl, and amine) possessing selective reactivity with heavy metal ions as the functional modifiers, this project is to design and fabricate desired organic-inorganic hybrid materials and construct highly active microporous materials with large size, multi-channel and high permeability, to reduce or eliminate the bioavailability of the heavy metal pollutants in soil, thereby realizing safe remediation of the contaminated soil..This project is to study the selective matching between as-synthesized organic modifiers and the nanoscale silica carrier as well as the synthetic technology of the nano-hybrid materials. Namely, the in-situ large-scale preparation technology and process of the hybrid materials will be developed, the correlations among the structure, composition, and distribution of the surface functional groups and their reactivity towards heavy metal ions as well as the passivation effect of the remediating products will be revealed. In the meantime, the stability of nanometer hybrid material-heavy metal complex in the soil as well as its influence on the migration behavior of heavy metal-plant will be investigated. Furthermore, the techniques to disperse nano-hybrid materials in the soil will be developed, and the efficient adsorption immobilization of the heavy metal pollutants will be realized. Upon completion of this project, the technological system with good environmental acceptability will be constructed for remediating the soil polluted by heavy metals in the presence of the as-synthesized nano-hybrid material as the cornerstone.

土壤重金属污染是我国目前亟待解决的重大环境问题，化学钝化重金属是修复污染土壤的主要途径之一。本项目针对铅、砷、镉、汞、铬等主要污染物，以与土壤环境有良好兼容性的纳米二氧化硅为载体，以与重金属离子有选择反应性的有机化合物（含巯基、二硫代羧基、胺基等官能团）为功能修饰剂，设计、制备有机-无机纳米杂化材料，并构建大尺寸、多通道、高透过性的活性微孔材料，用于降低或消除污染重金属的生物有效性，实现对污染土壤的安全修复。.研究功能性有机修饰剂与纳米微粒载体的选择匹配规律及合成方法，开发纳米杂化材料的宏量制备的原位表面修饰技术与工艺；揭示纳米材料表面官能团的结构、组成和分布与重金属选择反应性及钝化效应的关系规律；研究纳米杂化材料-重金属配合物在土壤环境中的稳定性及对重金属-植物迁移性影响规律。开发纳米杂化材料的土壤分散技术，实现对重金属的高效吸附固定。构建具有环境适应性的纳米杂化材料修复技术体系。

重金属污染土壤的修复治理是我国亟需解决的重大环境问题，化学钝化重金属是修复污染土壤的主要途径之一，但现有钝化修复剂多存在钝化效果不稳定或对土壤扰动较大的问题。本项目针对环境友好型原位钝化修复剂开展了如下的研究工作：.（1）以与环境具有良好兼容性的纳米二氧化硅为载体，在其表面化学键合与铅、砷、镉等重金属具有丰富配位功能的有机修饰剂，设计制备了重金属选择反应性有机-无机纳米修复剂；.（2）探索了表面官能团组成及表面结构与修复剂重金属钝化作用的构效关系；通过液相原位表面修饰技术实现对纳米微粒的粒径、比表面积、官能团分布等结构和性能的调控，并形成了RNS-SH、RNS-SF、RNS-FF三种型号的纳米修复剂产品；.（3）研究了纳米修复剂-重金属钝化产物在土壤环境中的稳定性及纳米杂化材料对重金属在土壤-植物间迁移行为的影响，证明钝化产物在极端酸雨条件或极端温度下仍具有良好的稳定性，且通过钝化作用能够降低重金属从土壤到植物的迁移，地表植物中重金属含量大幅度降低；.（4）所制备的纳米修复剂对土壤环境具有较低的扰动性，经修复后土壤微生物量、肥力等主要指标均明显向好，修复剂对已破坏的土壤环境具有一定的改良作用；.（5）开发了管线式可喂料微梯度乳化反应器和多功能剪切反应系统，探索了宏量制备过程中均匀传质和传热，实现纳米修复剂规模化生产。开发了纳米杂化材料的土壤分散技术及原位修复工艺，在济源、新乡等多个污染地块进行了大田修复实验，共修复农田12亩，修复后小麦籽粒中重金属含量下降60%以上，获得了很好的修复效果；.本项目利用二氧化硅纳米微粒为功能载体，官能团负载效率高，纳米修复剂与土壤环境有良好兼容性，对土壤环境扰动小，适用于大面积土壤的高效治理，显示了很好的应用前景。