基于堆肥污泥衍生腐殖质耦合电化学修复尾矿砷污染土壤的除砷机制

It has been found that humus substances with high redox activity could be extracted from the sludge composting, which raised new ideas for the transformation of sludge resource. This topic aims at those soil contaminated by tailings arsenic, which attempts to promote the release, migration and capture of arsenic in contaminated soil. It creatively puts forward the coupling technology of electrochemistry and humic process. It will explain the effects of different composting conditions on the macroscopic redox capacity and microscopic redox groups of humus, through the determination of electronic receiving/gift capacity and redox functional groups of different humus components (humic acid and fulvic acid). The redox reaction environmental law of humus will be revealed by comparison with the reaction kinetics study of common redox materials and the change of functional groups during the reaction. By adjusting the operating conditions, the functional groups and the changes of metal ions concentration of humus, humus-mineral and humus-mineral-arsenic phase before and after the reaction will be determined, which helps to explore the complexation mechanism and arsenic release law on iron/manganese mineral by humus. Through the correlation analysis of derivative humus and the performance change of arsenic (concentration, migration rate, migration flux) before and after the electrochemical treatment, the forms change and release law of arsenic in the solid phase and liquid phase of contaminated soil will be investigated. Ultimately, the release, migration and and transformation of arsenic in the contaminated soil strengthened by electrochemical process will be revealed.

已有研究发现污泥堆肥可提取高氧化还原活性的腐殖质，可以为污泥资源转化提供新的思路。本课题以尾矿砷污染的土壤为研究对象，以促进污染土壤中砷的释放、迁移捕获为主要目标，创新性地提出以电解耦合腐殖质工艺为技术手段，通过对腐殖质不同组分（腐殖酸/富里酸）电子接收/赠与容量、氧化还原官能团的测定揭示不同堆肥条件对腐殖质宏观氧化还原容量/微观氧化还原基团的影响规律；通过与常见氧化还原物质的反应动力学研究和反应中官能团的变化揭示腐殖质的环境氧化还原反应规律；通过控制不同操作条件，测定反应前后腐殖质、腐殖质-矿物相、腐殖质-矿物相-砷离子等不同体系中各种官能团及金属离子浓度的变化情况，探究腐殖质对铁锰矿物的络合机制及释砷规律；通过解析电化学处理前后，衍生腐殖质与砷性能指标（浓度、迁移速率、迁移通量）变化的相关关系，污染土壤固相和液相中砷的形态变化和释放规律，揭示电化学强化砷的释放、迁移转化机制。

目前世界范围内土壤砷含量超标问题突出，尤其在尾矿中五价砷与矿物金属结合体的污染最为严重，易造成巨大的潜在威胁。本研究以尾矿砷污染土壤为研究对象，以促进土壤中砷的迁移转化为主要目标，通过调控不同的堆肥条件（含水率、通气率、生物炭类型、生物炭投加量和不同投加阶段）得到具有最佳还原容量的腐殖质，结合不同的分析方法和有机物表征手段探究了可溶性有机物和腐殖质官能团的组分演变。利用从堆肥污泥中提取的不同腐殖质作为淋洗剂，明确了不同来源、不同成分的腐殖质对As污染土壤的淋洗修复效果，通过紫外/可见吸收光谱（UV-Vis）和傅里叶红外光谱（FTIR）分析腐殖质与As的作用效果，揭示了腐殖质修复As污染土壤过程中可能涉及的相关机理。探讨了环境因素（Fe（III）络合物种类、反应时间和pH）对腐殖质还原性的影响；同时利用三维荧光光谱进一步探究腐殖质结构，结合腐殖质的光化学指标（HIX、BIX、FI370），建立了腐殖质结构与还原性的关系。对比腐殖酸（HA）和富里酸（FA）促进砷移动的效果，分析伴生金属、砷和金属相关性以及砷的形态分布情况。研究了电动修复时间和腐殖质添加量对修复效果的影响，分析了电动修复过程中砷的迁移规律和修复后土壤的理化性质；进一步探究了腐殖质的不同组分对电动技术修复砷污染土壤的影响，研究不同电解液和阳极液pH控制对修复效果的影响，重点分析修复过程中土壤pH、电导率和土壤砷的残余量随时间和空间的变化规律，记录修复后土壤含水率和土壤孔隙水Eh的分布情况，最后阐明了腐殖质强化电动技术去除土壤砷机理。