类水滑石中金属价态变化对重金属固定性能与表面反应性的影响

Layered double hydroxides (LDHs), a type of anionic clay, are easily formed by the interaction between divalent heavy metal ions and the widely existing elements of aluminum and iron in the soil. The formation of LDHs shows significant environmental meaning. On one hand, heavy metal ions can be immobilized into the structure of LDHs in their formation process, which presents great benefit in reducing bioavailability of heavy metals. On the other hand, LDHs possess high surface reactivity, which favors the purification of environmental contaminants. Whether LDHs have long-term effectiveness in immobilizing the heavy metals in their structure and retaining the surrounding environmental contaminants depends on their physicochemical stability under the subsequent geochemical evolution process. In this project, the effects of the variation of chemical valence of metal components of LDHs toward the immobilized ability of heavy metals and surface reactivity are proposed to be studied. LDHs composed by divalent heavy metal cations and Al(III) are first synthesized, which then suffer several times of redox reaction. After every redox reaction, the changes of structure of LDHs, the changes of speciation and distribution density of heavy metals will be investigated. Additionally, the change of the proportion of extractable heavy metals to the total heavy metals will be emphatically investigated to reveal the relationship between the structure of LDHs and the release of heavy metals. Furthermore, the changes of surface reactivity of LDHs after geochemical evolution process will be studied by adsorptive and photocatalytic experiments, trying to disclose the relationship between the structure of LDHs and surface reactivity. The results of this project have important referential value for evaluating the environmental significance of LDHs and developing in-situ control technology of heavy metals.

重金属离子与土壤中广泛存在的铝、铁等元素作用容易形成阴离子黏土类水滑石。类水滑石对环境自净化具有重要作用，一是可在形成过程中将重金属固定在结构中；二是具有高表面活性，是天然地质吸附剂和催化剂。类水滑石的结构稳定性制约着其结构中重金属的迁移、转化和环境毒害性，同时影响类水滑石的表面反应活性。本项目拟通过探讨类水滑石在地球化学演化中发生氧化还原变化对其结构的影响，揭示结构变化对重金属锁定以及表面反应性的影响，阐明类水滑石可能的长期环境行为。项目从研究类水滑石的结构变化、重金属的赋存形态及分布密度变化、可提取态重金属含量变化等方面入手，建立重金属固定能力与类水滑石结构变化的联系以及可提取态重金属含量与重金属赋存形态的关系。在探明类水滑石结构变化基础上，通过污染物吸附与光催化实验探讨类水滑石表面反应性的变化，确立结构与表面反应性的关系。项目研究成果对评估类水滑石的环境价值具有重要参考意义。

类水滑石对环境污染净化具有重要的价值，但其长期环境性能与环境演化的关系尚不明确。基于此，项目探究氧化还原环境的演变对类水滑石结构和净化污染物能力的影响。研究结果揭示了氧化还原交替演化有助于消除杂质相并促进类水滑石结构的形成，有助于消除碳酸盐结合态等重金属赋存形态并促使转变为残渣态，由此使得类水滑石结构中的重金属元素与类水滑石结构结合更加紧密，增强重金属元素的结构锁定性能，降低重金属的迁移性和生物可利用性。总体而言，项目明确了氧化还原演化会显著改变类水滑石的结晶程度、电子结构特性、结构元素的占比与占位、结构电荷含量、表面微结构、结构中金属/重金属元素的赋存形态等，由此改变类水滑石的表面反应活性以及对其结构中重金属元素的锁定性能。从长期环境地球化学演化来看，类水滑石可作为重金属离子稳定的汇，能够长期稳定的固定其结构中的重金属离子，具有重要的环境价值；但类水滑石的氧化还原演化会降低类水滑石的对外来重金属的表面吸附和有机污染物的催化活性，降低类水滑石对其所处周围环境污染物的净化能力。在后续的环境重金属污染治理作业中，可尝试促进重金属离子形成类水滑石矿物，从而实现重金属离子的固定化或资源化回收。项目明确了重金属固定能力与类水滑石结构变化的关系、可提取态重金属含量与重金属赋存形态的关系、类水滑石表面反应性与结构变化的关系，研究数据可为评估演化进程下类水滑石长期环境价值提供基础信息。研究已发表SCI论文3篇，申请相关发明专利1项。

内容获取失败，请点击重试