钒(V)在土壤中微纳米胶体易化运移机制研究

Vanadium is a mobile element, while, it is lack of systematical and deep investigations on fate and transport of vanadium in soils, particularly with respect to colloid-facilitated vanadium transport. Furthermore, understanding of colloid-facilitated transport of pollutants in "solid-liquid-colloid" triple phases will advance the development and refinement of pollutant migration theory. Currently, there is a knowledge gap in understanding the effects of properties of colloids as well as surface of porous media on colloid-facilitated contaminant transport in soils. This proposal will reveal the controlling factors and mechanisms of colloid-facilitated transport of vanadium in intact soils, and clarify both dynamic and static sorption and desorption mechanisms of vanadium on different types of soil colloids. Vanadium contaminated and uncontaminated intact soil columns of different textures and types will be sampled and used in the study. In addition, quartz sand with different size distributions will be used to simulate natural porous media. The sand soil will be modified with chemical and physical methods to obtain different surface properties. Both the batch sorption experiment and the column transport/leaching experiment will be carried out with simulated rainwater and vanadium contaminated solution. The PI and his group are highly qualified and well-prepared to conduct the proposed research. It is expected that the success of this project will advance the fundamental theory to better predict and monitor vanadium temporal and spatial distributions in soils and other porous media; furthermore, it will improve current understanding of theories of colloid-facilitated contaminant transport. It is also anticipated that the proposed project will provide important theoretical and practical guidance to protect soils from vanadium contaminations.

钒是可迁移元素，土壤中钒的运移和归宿缺乏系统深入的研究，尤其是钒的胶体易化运移研究。而胶体易化运移理论则是对污染物迁移理论的完善与发展，目前存在的问题是该理论中胶体的粒径和成分及介质表面性质的影响不够明确。为了完善胶体易化运移的理论，揭示钒在原状土壤中的胶体易化运移机制及影响因素，阐明不同类型土壤胶体对钒的动态与静态吸附解吸机制。本研究拟采集不同质地及类型土壤的未污染或钒污染的原状土柱，利用砂柱模拟不同粒径的多孔介质，通过对风沙土的处理实现不同表面性质的介质，开展不同性质的模拟降雨以及钒污染溶液的柱淋洗和吸附解吸实验。申请人及研究组成员具有扎实的研究基础能够保证本项目的顺利完成。该项目的完成将为钒在土壤中空间分布学科的发展奠定理论基础，进一步丰富"固-液-胶体"三相体系中污染物的胶体易化运移理论，同时对污染土壤中钒的防治具有重要的理论和实际意义。

项目围绕钒在土壤及模拟地下水环境中微纳米胶体作用下的归趋开展研究工作，采集风沙土、黄绵土、塿土、黑垆土、黄褐土、潮土，提取纳米土壤胶体颗粒，制作改性生物炭作为钒的吸附解吸材料，对风沙土处理得到不同表面性质的运移介质，运用石英砂柱进行模拟饱和多孔介质。通过研究明确了钒在土壤及土壤纳米胶体上的吸附量、解吸量，吸附解析规律及pH、IS的影响。阐明了钒在饱和石英砂柱及饱和风沙柱中运移的机制，查明了pH、IS、流速对饱和石英砂柱及饱和风沙柱中运移的影响规律。这些研究结果表明，土壤纳米胶体颗粒对钒在多孔介质中的运移起到一定的促进作用，并且钒的运移在土壤及饱和多孔介质中受到诸多外界因素的影响，本研究结果对钒在环境中的归趋模式及污染控制具有重要的意义。.主要研究结论如下：.1、土壤纳米胶体对钒的吸附要远远高于土壤对钒的吸附。不同土壤及土壤纳米胶体对钒的吸附动力学均最符合二级动力学模型，对钒的等温吸附最符合Langmuir模型，说明土壤及土壤纳米胶体对钒的吸附主要是单分子吸附。.2、传统的溶质运移模型可以用来模拟钒在饱和多孔介质的运移｡钒的运移能力随着离子强度、pH的升高(4~8)而提高；多孔介质中粘土矿物胶体能够加速钒的移动，蒙脱石胶体对钒运输的促进作用高于高岭石胶体。不同的运移过程中胶体与钒的相关性均进一步表明移动的胶体可以作为吸附剂清除残留在多孔介质中的钒污染物。.3、离子强度、pH和流速对钒在风沙土中的运移有显著的影响。离子强度和pH的升高有助于钒在风沙土中的运移。低流速促进钒和土壤纳米胶体在风沙土中运移，高流速不利于钒和胶体的运移。.4、生物炭虽然有丰富的孔隙结构，相当大的表面积和特殊的表面化学性质，可以用来吸附很多重金属，但是对(VO4)3—络阴离子的吸附性能非常小。通过载铁改性后生物炭对钒的吸附量为13.4110mg•g-1和远远高于未改性生物炭对钒的吸附(0.8717 mg•g-1) 。