还原型施氏矿物可控制备及其对土壤中铬的长效稳定化机理研究

Chromium is one of the key regulatory pollutants for soil pollution control in China. The high-efficiency, secure, and long-term stabilization for chromium contaminated soil is an important conundrum of soil remediation. It is difficult to achieve the long-term stabilization for chromium by the single chemical reduction reaction. The research and development of stabilization material with excellent performance is the key to solving the technical difficulties. In this research, based on the schwertmannite with high adsorption capacity for chromium, columnar channel structure, and high specific surface area, the preparation strategies and reaction process control of the reductive schwertmannite with both reduction and adsorption properties will be confirmed. The crystal formation and transformation process of reductive schwertmannite will be revealed by the in-situ characterization means. The reaction product of reductive shwertmannite and chromium will be analyzed through the methods of macroscopic behavior, microstructure characterization, and model simulation. And then the mechanisms and process of interface reaction between reductive shwertmannite and chromium will be illuminated based on the chromium speciation transformation between surface and channel structure of mineral for ion exchange, coordination complexation, and electron transfer. The lon-term stabilization and control mechanisms of chromium in soil will be elaborated through the analysis of the desorption process and product between reductive shwertmannite and chromium and the model simulation of chromium speciation. This project will advance fundamental researches and promote technological strategies for the research and development of chromium stabilization material in contaminated soil.

铬是我国土壤污染防治重点监管的污染物之一。铬污染土壤的高效、安全与长效稳定化是土壤修复领域的重要难题，目前广泛使用的快速单一的化学还原作用方式很难实现铬的长效稳定化，性能优异修复材料的开发是解决该难题的关键。本项目以施氏矿物为基础，研究以铬高吸附性能、柱状孔道结构、高比表面积为目标的施氏矿物可控制备方法，明确施氏矿物负载掺杂还原态铁的制备兼具还原-吸附性能的还原型施氏矿物的工艺，采用原位表征手段探究其晶相形成演变过程，实现其可控制备；综合利用宏观行为、微观表征、模型模拟等手段研究铬在矿物表面和孔道中的离子交换、配位络合、电子转移等反应过程，揭示铬还原-吸附的界面反应过程和稳定化机制；研究矿物与铬络合体的解吸过程与解吸产物，定量分析与模拟计算稳定化土壤中铬赋存形态、铬迁移受控相，阐明还原型施氏矿物对土壤铬的长效稳定化机制与调控原理。本研究将为铬污染土壤的长效稳定化修复材料开发提供科学依据。

项目针对我国铬污染土壤的高效、安全与长效稳定化的需求以及铬修复材料研究的前沿领域，主要研究了具有柱状孔道结构和高比表活性的对铬具有高效吸附性能的施氏矿物可控制备方法，明确兼具还原-吸附性能的还原型施氏矿物的制备工艺，综合利用宏观行为、微观表征、模型模拟等手段研究了铬在矿物表面和孔道中的离子交换、配位络合、电子转移等反应过程，揭示了铬还原-吸附的界面反应过程和稳定化机制;分析矿物与铬络合体的解吸过程与解吸产物，研究施氏矿物与铬结合的稳定性；通过实际铬污染土壤，阐明还原型施氏矿物对土壤铬的长效稳定化机制。项目主要研究成果包括：（1）探明了施氏矿物与铬吸附之间的构效关系并形成了适用于铬修复的施氏矿物快速可控化学制备方法；（2）揭示了施氏矿物的矿物学特征以及对铬的吸附行为；（3）明确了浸渍法制备兼具还原-吸附性能的还原型施氏矿物Fe(II)@Sch的制备工艺，并显著提升了对铬的吸附性能；（4）吸附铬抑制了施氏矿物向针铁矿等其他矿相的转化，增强了施氏矿物的稳定性，从长效性角度表明了施氏矿物具有应用于土壤铬修复的潜力；（5）以实际铬污染场地土壤为研究对象，通过加速老化实验证实了施氏矿物以及Fe(II)@Sch对土壤铬具有长效稳定性。本项目成果对铬修复材料研发推广和实际污染场地修复治理具有重要的理论意义和技术支撑。