以河道底泥为基体的重金属稳定化机理研究

MECHANISMS OF HEAVY METAL IMMOBILIZATION IN THE MATRIX OF RIVER SEDIMENTS

邱栋

11849067

硕士

环境科学与工程

唐圆圆

2020-05-31

2020-05-31

哈尔滨工业大学

深圳

工业化进程的加快在提高人们生活便利性的同时也带来一系列环境问题，其中重金属污染因其具有毒性危害大、生物富集性强等特点越来越受到人们的关注。河流所接纳的污/废水中含有大量重金属离子，这些重金属会经沉淀、吸附、络合等物理化学作用沉积在河道底泥中，并逐渐累积。当外界条件发生变化时，沉积在底泥中的重金属极易释放出来，产生一系列环境危害。因而对受重金属污染的河道底泥进行绿色高效的处理处置就显得尤为重要。 底泥疏浚作为一种能彻底去除污染底泥进而有效改善水体水质的工程措施，正得到越来越广泛的应用。伴随着经济社会的进一步发展，填埋、堆肥等传统的疏浚底泥处理手段局限性愈加明显，因此发展针对河道疏浚底泥的无害化、资源化处理处置手段显得迫在眉睫。然而，受污染疏浚底泥中含有的大量重金属污染物又极大地限制了底泥的资源化利用。已有研究表明，河道疏浚底泥中Al2O3、SiO2、Fe2O3等无机组分含量丰富，可以替代黏土作为陶瓷生产的原料，同时陶瓷烧结过程中生成的铝硅酸盐等产物相又可起到重金属稳定化的作用。因而，以河道底泥为原料经高温烧结过程制备相应的陶瓷产品，可以在达到良好的重金属稳定化效果的同时实现固体废物的有效资源化利用。 因此，本研究将探讨陶瓷烧结过程中重金属在河道疏浚底泥中的稳定化机理，研究建立模拟体系，将河道疏浚底泥分别与氧化镉以及氧化镉、氧化铅、氧化镍按照一定摩尔配比混合，并将混合后的样品在不同温度下进行烧结制得相应产品。研究进一步借助XRD、SEM-EDX、ICP-AES等分析测试手段，对两种混合体系下所制备的产品进行了从结构到性质的完整表征，既对重金属在以河道底泥为基体的复杂体系中的迁移转化行为及稳定化机制进行了较为深入的探究，也对烧结产品在较为严苛的酸性介质中长期存在时自身结构的稳定性及各元素自身浸出特性进行了完整的检验和评估。实验过程中还通过调整产品制备过程中的相关参数，验证了外界因素对于产品结构和性质的影响。 研究结果表明，不管是底泥与镉组成的单金属体系还是底泥与镉、铅、镍三种重金属组成的多金属混合体系，重金属都可以在以河道底泥为基体制备得到的烧结产品中达到稳定化状态。从重金属迁移转化的角度来看，对于单金属体系而言，烧结温度较低时重金属镉的持有相以金属氧化物和硅酸盐类为主，到达一定温度后，镉会结合进入铝硅酸盐结构达到更为稳定的状态。原料配比的不同会导致生成不同的最终赋存产物。具体而言，重金属镉的含量较高时，一次反应生成的含镉相会进一步与氧化镉结合生成一系列含镉的二次产物；镉含量较低时，氧化镉则会较多地与底泥中组分发生反应，产物相也多为含镉的一次产物。对于多金属混合体系，三种重金属（镉、铅、镍）可以通过与河道底泥中的组分反应生成铝硅酸盐或者三种重金属间彼此发生固相反应生成结构更为稳定的尖晶石结构而被有效地稳定。从烧结产品微观形貌的变化角度来看，烧结温度对于单金属和多金属混合体系下产品的微观形貌都有着显著影响：低温烧结的产品结构松散，致密性较差，而较高温度烧结产品结构则变得更加密实，并且高温会推动固相反应的进行进而促使产品表面衬度差异更为明显。从酸性介质中样品主要元素的浸出行为角度来看，较高的烧结温度下得到的样品各元素均有着较低的浸出率，重金属元素间以及重金属元素与体系中其他主要元素间都存在着对于H+的竞争，并且这种竞争以烧结产品中重金属的稳定性变化为主导，其他元素的浸出量随着重金属在产品中的稳定性变化产生相应的趋势上的变化。

The acceleration of the industrialization process has caused a series of environmental problems besides improving the convenience of people's lives. Among them, heavy metal pollution has attracted more and more attention because of the toxic hazards and strong bioaccumulation. The wastewater received by the river usually contains a large amount of heavy metals, which will be deposited in the sediment of the river channel through physicochemical effects such as precipitation, adsorption and complexation, and gradually accumulate. When the external conditions change, the heavy metals deposited in the sediment are easily released, resulting in a series of environmental hazards. Therefore, it is particularly important to carry out green and efficient treatment and disposal of river sediment contaminated by heavy metals.Sediment dredging is an engineering measure that can completely remove contaminated sediment and effectively improve water quality. With further development of economy and society, the limitations of traditional dredging sediment treatment methods such as landfilling and composting have been becoming more and more obvious. Therefore, it is urgent to develop harmless and resource-based treatment methods for river dredging sediments. However, the large amount of heavy metal contained in the contaminated dredged sediment greatly limits the resource utilization of the sediment. Existing studies have shown that the oxdies of Al/Si/Fe and other inorganic components are mainly contained in the river dredging sediments, which can replace clay as a raw material for ceramic production. At the same time, the product phases such as aluminosilicate generated during ceramic sintering can also interact with heavy metals contained in the reaction matrices. Therefore, the preparation of ceramic products from river sediment as raw material by high-temperature sintering can effectively recycle the solid wastes while achieving a good heavy metal stabilizing effect.In this study, river dredging sediments were mixed with cadmium oxide, cadmium oxide, lead oxide, and nickel oxide according to a certain molar ratio and sintered to produce corresponding products. With the help of XRD, SEM-EDX, ICP-AES and other analytical testing methods, the structure and properties of the sintered products were fully characterized. The transformation behavior and stabilization mechanisms of the heavy metals in a complex sediment-based system were explicated in detail. Moreover, a prolonged leaching experiment was conducted on the sintered products, with the evaluation on the metal stability in the harsh acidic medium. During the experiment, the relevant parameters in the product preparation process were adjusted to verify the influence of external factors on the product structure and properties.The results show that whether in the monometallic system composed of sediment and cadmium or the multimetal system composed of sediment cadmium, lead and nickel, heavy metals can be effectively immobilized in the sintered products. From the perspective of migration and transformation of heavy metals, for monometallic system, the holding phase of cadmium is mainly oxide and silicates when the sintering temperature is low. After reaching certain temperature, cadmium will combine into aluminum silicon then become more stable. The ratios of raw material will have an effect on the end products. Specifically, when the content of cadmium is high, the cadmium-containing phase generated by the first reaction will further combine with cadmium oxide to form a series of cadmium-containing secondary products; while the primary products which contain cadmium will be the dominant phase when the the content of cadmium is low. For multimetal system, three kinds of heavy metals (cadmium, lead, nickel) can not only react with the components contained in the sediments to form aluminosilicate but also react with each other to generate spines which have a more stable structure. From the perspective of the sintered products' micromorphology, the sintering temperature has a significant effect on the micromorphology of the product in both two system. The products which are sintered in low temperature has a loose structure and poor compactness, while structure of the products which are sintered in the higher temperature is denser. Meanwhile, the high temperature will promote the solid-phase reaction so that the difference of surface contrast will be more obvious. From the perspective of the leaching behavior of elements, the produts which is sintered in high temperature has a lower leaching rate than that in low temperature. Moreover, there is competition for H+ between heavy metal elements and between heavy metal elements and other major elements in the river sediments. And the competition is dominated by the stability change of heavy metals. The leaching concentration of other elements change with the stability change of the heavy metals

河道底泥 重金属 稳定化 陶瓷烧结

river sediments heavy metal immobolization ceramic sintering

中文

联合培养

南方科技大学

邱栋. 以河道底泥为基体的重金属稳定化机理研究[D]. 深圳. 哈尔滨工业大学,2020.