硫铁改性生物炭(S-Fe@Biochar)对中碱性土壤镉（Cd）稳定化过程界面行为的调控机制研究

Nowadays, cadmium (Cd) contamination of neutral-alkaline agricultural soils has attracted public attention. Meanwhile, the remediation of Cd-contaminated agricultural soils has become the priority of current environment protection works for both authorities and scientific institutions. However, the scarcity of effective immobilization agents significantly restricted the conduction of such works. Recently, the sulfur-iron modified biochar (S-Fe@Biochar) has been regarded as a promising candidate for soil heavy metal immobilization. However, mechanisms of Cd stabilization under the influence of this reagent in either short or long terms are still unclear. Therefore, in this study, the influence of S-Fe@Biochar on Cd immobilization in neutral-alkaline soils will be investigated following the combined methods (including batch adsorption experiment, incubation experiment, and pot experiment) and characterized using novel spectrum analysis techniques. The whole work can be divided into three parts: 1) investigating the interface interaction between Cd2+ and S-Fe@Biochar in aqueous solutions; 2) exploring the influence of simulated biochar oxidation on the reaction between Cd2+ and S-Fe@Biochar, and 3) analyzing the effect of S-Fe@Biochar on Cd immobilization in neutral-alkaline soils. The aim of the study is 1) to indicate the mechanism of S-Fe@Biochar on Cd immobilization in neutral-alkaline soils; 2) to specify the reaction process, driving factors, and mechanisms between Cd2+ and S-Fe@Biochar in both short and long terms; and 3) to develop a soil remediation theory based on the relation between S-Fe@Biochar and Cd mobility/specification in soils. The successful completion of this project will supplement soil heavy metal stabilization theory, expand biochar environmental application, and be meaningful for guaranteeing soil quality, food safety as well as reducing the threat of Cd to human beings.

中碱性农田土壤的镉（Cd）污染已经引起了社会的广泛关注，开展污染土壤的修复与治理迫在眉睫。但是，修复材料的缺乏制约了土壤修复工作的开展。硫铁改性生物炭（S-Fe@Biochar）是一种潜在的土壤Cd稳定化材料。然而，有关该材料对土壤Cd稳定化的作用机制和驱动因子尚缺乏深入系统的研究。基于此，本项目立足前期研究工作，在研发并优化S-Fe@Biochar的基础上，采用批试验、培养试验与盆栽试验相结合的方法并利用现代光谱分析技术，解析材料与溶液中Cd2+的微界面化学过程；剖析生物炭氧化过程中Cd2+与材料组分的微界面作用机制；揭示材料稳定化中碱性土壤中Cd的作用机制和驱动因子并评估材料对污染土壤的修复效果。从而提出基于S-Fe@Biochar表面特性—土壤Cd形态/有效态耦合作用的污染土壤修复理论。这对完善重金属污染农田土壤稳定化修复的理论体系，保障区域土壤环境质量与农产品安全等均具有重要意义。

中碱性农田土壤的镉（Cd）污染已经成为了当前亟待解决的环境问题之一。生物炭作为一种环境友好材料，在Cd污染土壤稳定化修复方面展现了极大的应用潜力。但是，生物炭对中碱性土壤中Cd的钝化效果有限，对于生物炭驱动土壤Cd长效稳定化的作用机制还不清楚。因此，本研究以硫铁改性生物炭(S-Fe@BC)为修复材料，采用批试验、培养试验与盆栽试验相结合的方式并利用现代光谱分析技术，研究稳定化过程中S-Fe@BC与中碱性污染土壤中Cd的相互作用机制和驱动因子。研究发现：1）裂解温度、原料组成以及功能基团的负载方式是决定材料的理化性质和吸附性能的关键指标；2）老化过程中含氧官能团的增加能够提升生物炭对土壤中Cd的固定，然而功能基团的消耗（溶解、氧化和与其他阳离子螯合）是改性生物炭性能降低的主要因素；3）改性处理能够显著提升生物炭对溶液和土壤中Cd的固定，其中nZVI@BC能够快速但不持久地固定土壤中的Cd，而S-Fe@BC能够高效且长效固定土壤中Cd；4）静电吸附、离子交换、沉淀和螯合作用是S-Fe@BC高效且长效固定土壤Cd的主要机制。项目的实施可以拓展生物炭的环境应用，进一步完善重金属污染土壤修复的相关理论，为保障区域土壤环境质量与农产品安全等提供科学依据。