基于阴离子捕获的人工湿地LDHs涂层负载填料对水体中典型重金属离子协同净化机制

In recent years, large-scale water pollution crisis outbroke frequently caused by heavy metal emissions exceed the standard. Research of purification and separation technology effectively for toxic heavy metal ions in water body are needed urgently. As constructed wetland technology applied increasingly in ecological restoration of contaminated water, the research of substrate modified in order to improve the effect of purification begin to receive attention seriously.This research is aiming at common vertical-flow constructed wetland substrate such as anthracite, zeolite and so on, which are coating modified by special LDHs film. As the typical and biological-toxic heavy metal ions in contaminated water, purification effect of Cr(VI) and Cd(II) will be studied using LDHs coating modified substrate base on the theory of anionic capture and bio-stimulus response function. The changes of the physico-chemical and biochemistry properties in the substrate before and after modification and the differences of purification will be contrasted. The analysis on the purification mechanism of toxic heavy metal ions treated with modified substrate will be carried out. Based on the LDHs coating type and heavy metal contamination, the ecological response model of wetland microbial community will be established. The synergistic effect of purification for main heavy metal pollutants among LDHs coatings, substrates and microorganism characteristics will be revealed. And in order to achieve the purpose of efficient eco-restoration on the water polluted by different types of heavy metal with different modified substrate, the purification mechanism of different types of heavy metal ions treated by different LDHs modified substrate will be explored.

近年来，重金属超标排放导致大规模水污染危机事件频发，水体中有毒有害重金属离子有效、高效净化与分离技术的研发刻不容缓；随着人工湿地广泛应用于受污染水体的生态修复，对人工湿地系统净化主体之一的填料进行适当改性以提高净化效果的研究开始受到重视。本项目以常用垂直流人工湿地填料为研究对象，利用LDHs的特殊构型对填料进行涂层修饰，研究具有阴离子捕获功能和生物刺激效应的LDHs负载于填料表面后，改性填料对Cr(VI)与Cd(II)净化功能的提升及其微生物响应特征；通过对比改性前后及净化周期前后，原始与改性填料物化、生化特性的变化，探寻LDHs涂层负载填料净化重金属离子的作用机理，建立以LDHs涂层特性和重金属污染物类型为基础的湿地微生物群落生态响应模型，揭示LDHs、填料及微生物对水体中典型重金属离子的协同净化机制，以期达到采用有针对性的填料改性方式高效净化受不同类型重金属离子污染水体的目的。

兼具生态和景观效应的人工湿地技术近年来已广泛应用于水体生态修复、污水处理厂尾水深度净化、分散型农村生活污水处理等领域。针对现有人工湿地常用填料对水体中重金属污染物去除效率偏低，易吸附饱和的问题，本项目提出了利用层状双金属氢氧化物LDHs特殊构型所具有的阴离子捕获能力和生物刺激效应，采用不同金属化合物合成各种LDHs并涂层负载于常用人工湿地填料表面，以增强人工湿地对重金属离子的净化效果，提升重金属污染物的治理能力。. 课题组通过将Zn2+、Mg2+和Fe3+、Al3+的氯化盐及碳酸盐化合物一一配对反应的方式，利用水浴-共沉淀法合成不同类型LDHs并即时涂层负载于沸石、石英砂、麦饭石等3种人工湿地常用填料表面；分别针对受污染水体中的Cr(VI)和Cd(II)，开展各种原始及改性填料的净化实验、吸附试验及微生物实验。经过4年多的实验研究，验证了不同类型的氯系及碳酸系LDHs改性填料去除水体中以阴离子或阳离子形态存在的重金属污染物各不相同的提升能力；确定了LDHs涂层负载填料对水体重金属污染物的去除以吸附性能的提升为主，并同步增强微生物对重金属离子耐受能力的协同作用机制：基于吸附性能提升的阴离子捕获作用，促进了以铬酸根为代表的水体重金属阴离子的有效去除；基于LDHs负载的微生物耐受能力增强，有助于以镉离子为代表的水体重金属阳离子的生物去除。. 本研究为如何使人工湿地技术有效运用于受重金属污染水体的生态修复中提供了新的理论基础、技术路线和实践参考。针对水体中不同存在形式的重金属污染物，可通过筛选合适的LDHs类型并涂层负载于不同种类原始填料的方式，达到利用填料的改性与强化，定向去除水体主要污染物、增强人工湿地综合净化效果、拓展人工湿地应用领域的目的。