铬盐生产污染场地含水层水—岩界面铬迁移转化研究

发布时间：2019-02-09 12:00

【摘要】：近年来,随着铬矿的开采和冶炼,铬盐的加工制造,印染、制革等行业迅速发展,铬成为环境中重要的重金属污染物。铬盐生产过程中的跑冒滴漏和铬渣堆防护措施的缺失,使得铬盐生产场地成为我国地下水铬污染最严重的区域之一。铬化合物进入地下水-岩系统,受铬的存在形态、地下水赋存状态及地下水水质、含水层介质理化性质等多种因素影响,在地下水-岩界面发生迁移转化,研究其迁移转化规律,对修复和治理被铬污染的地下水具有重要的指导意义。本研究针对陕西商南铬盐生产场地铬渣堆污染问题,开展了关于堆存铬渣理化性质、铬渣浸出毒性及铬在水-岩界面迁移转化的一系列批实验和柱实验研究,实验结果表明:(1)铬渣颗粒粒径分布不均匀,经过风化以后,表面密实。铬渣浸出液中铬元素主要以Cr(VI)的形式存在,每千克的铬渣中约含有6.7gCr(VI)。铬渣浸出液的pH较高,且浸取剂pH对铬渣浸出液pH影响不大,酸性浸取剂更易使Cr(VI)释放出来。(2)由于不同土壤介质的理化性质不同,Cr(VI)在其中的迁移转化机制也不相同。亚粘土、红壤和黄土对Cr(VI)的吸持量与含铬溶液初始浓度有一定的相关性。实验的三种土壤介质对Cr(VI)的吸持过程均可采用Langmuir和Freundlich方程进行拟合。拟合结果说明,亚粘土和红壤表面可能存在不同类型的吸附位,且这些吸附位对Cr(VI)的结合力不同,而黄土的吸附行为可能为单分子层吸附;Cr(VI)在三种土壤介质中的吸持过程都能够采用准二级反应动力学方程进行拟合,表明吸持由化学反应过程主导。(3)亚粘土、红壤和黄土介质对含铬溶液中铬的吸持作用主要包括:吸附作用、还原作用、络合作用。当含铬溶液浓度超过地下水质量标准10倍时,三种土壤对Cr(VI)的吸持能力大小为:红壤亚粘土黄土。吸持后,三种土壤介质中残渣态铬所占比例均为最大,且不易释放,水溶态和可交换态较少,其他形态存在比例与土壤介质的有机质含量、铁、锰、铝氧化物含量等有关。(4)当pH小于12时,亚粘土、红壤和黄土对含铬溶液pH的变化具有一定的缓冲能力。另外,外源有机质的添加量对铬的吸持影响也较大。
[Abstract]:In recent years, with the mining and smelting of chromium ore, the processing and manufacture of chromium salt, printing and dyeing, leather making and other industries, chromium has become an important heavy metal pollutant in the environment. Because of the leakage of chromium salt and the lack of protection measures, chromium salt production site has become one of the most seriously polluted areas in China. Chromium compounds enter the groundwater rock system, which are affected by the existing form of chromium, the state of groundwater occurrence and groundwater quality, the physical and chemical properties of aquifer media, and so on, and the migration and transformation take place at the interface between groundwater and rock. The study of its migration and transformation is of great significance for remediation and treatment of chromium contaminated groundwater. A series of batch and column experiments on the physicochemical properties of chromium slag, leaching toxicity of chromium slag and migration and transformation of chromium at water-rock interface were carried out to solve the pollution problem of chromium slag in Shangnan chromium production site in Shaanxi Province. The experimental results show that: (1) the particle size distribution of chromium slag is not uniform and the surface is dense after weathering. Chromium is mainly in the form of Cr (VI) in the leachate of chromium slag, and there is about 6.7gCr (VI). In every kilogram of chromium slag. The pH of chromium residue leachate was high, and the leaching agent pH had little effect on pH, and acid leaching agent could release Cr (VI) more easily. (2) the physicochemical properties of different soil media were different. The migration and transformation mechanism of Cr (VI) is also different. There is a certain correlation between the absorption of Cr (VI) and the initial concentration of chromium-containing solution in the clay, red soil and loess. The sorption process of Cr (VI) in three soil media was fitted by Langmuir and Freundlich equations. The fitting results show that there may be different types of adsorption sites on the surface of subclay and red soil, and the binding forces of these sites to Cr (VI) are different, while the adsorption behavior of loess may be monolayer adsorption. The adsorption process of Cr (VI) in three kinds of soil media can be fitted by quasi-second-order reaction kinetic equation, which indicates that adsorption is dominated by chemical reaction process. (3) Clay. The adsorption of chromium in chromium-containing solution by red soil and loess medium mainly includes adsorption, reduction and complexation. When the concentration of chromium-containing solution exceeded the groundwater quality standard by 10 times, the absorbability of Cr (VI) to the three soils was as follows: the red soil subclay loess. After sorption, the proportion of residual chromium in the three kinds of soil media was the largest, and it was not easy to release, the water soluble and exchangeable forms were less, and the other forms were related to the content of organic matter, iron, manganese, iron and manganese in the soil media. (4) when pH is less than 12:00, the changes of pH in chromium-containing solution can be cushioned by subclay, red soil and loess. In addition, the addition of exogenous organic matter has a great effect on the absorption of chromium.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X523

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