水介质条件下不同粒径的铀尾矿中铀元素释放的实验研究

发布时间：2018-04-28 02:15

本文选题：铀尾矿 + 铀元素　；参考：《南华大学》2015年硕士论文

【摘要】：铀尾矿中铀元素的释放受粒径影响非常大。酸法提铀过程中,铀元素的提取率与粒径有很大关系,与尾矿中铀的残留量更是有直接关联;水是尾矿中铀释放最主要的动力之一,而粒径是影响尾矿与水接触面积的关键性因素。在我国南方降雨丰沛、地下水系运动复杂的地理条件下,研究粒径对铀元素释放的影响很有必要。本论文采用静态浸泡实验,模拟自然环境中,粒径对浸泡在地下水层的尾矿中铀元素释放的影响;采用动态淋浸实验,模拟自然环境中,粒径对受到降水淋浸作用的浅层尾矿中铀元素的浸出,并对其动力学特征进行探究。通过实验得到以下结论:1.分析了粒径对尾矿中铀释放过程的影响。通过对我国南方某铀尾矿库的尾矿样品进行了静态浸泡实验和动态淋浸实验,模拟了库区环境中,研究不同的尾矿—水共存体系中,粒径对铀元素释放的影响。实验结果表明:(1)静态浸泡条件下,不同粒径铀尾矿中铀的释放过程类似,粒径对尾矿中铀的释放过程影响不大;动态淋浸条件下,尾矿粒径越小,铀的释放过程进展越快。(2)尾矿粒径越小,铀元素浸出速率越大。但粒径越小,静态浸泡条件下,尾矿越容易出现板结,影响铀元素的释放。(3)尾矿粒径越小,饱和阶段溶液中铀浓度各个阶段的铀浓度差距越小,整个铀释放过程越稳定,铀浓度波动越小,更利于长期贮存。2.对尾矿中铀的释放过程进行了浸出机制和动力学分析。模拟了实验过程中,铀元素浓度变化现象,运用了有限元回归方法对实验数据进行分析,指出在不同的尾矿—水共存体系中,铀元素释放的动力学机制存在差异。模拟结果表明:(1)尾矿表面附着的铀酰离子是导致尾矿中铀元素快速溶出的主要来源。(2)静态浸泡条件下,尾矿中铀的释放符合未反应收缩核模型特征;动态淋浸条件下,表面洗脱是尾矿中铀释放的主要形式。
[Abstract]:The release of uranium elements from uranium tailings is greatly affected by particle size. In the process of acid extraction of uranium, the extraction rate of uranium is closely related to the particle size and the residual amount of uranium in the tailings, and water is one of the main driving forces of uranium release in the tailings. The particle size is the key factor affecting the contact area between tailings and water. It is necessary to study the effect of particle size on uranium release under the geographical conditions of abundant rainfall and complicated movement of underground water system in southern China. In this paper, static immersion experiment was used to simulate the effect of particle size on uranium release from tailings immersed in underground water layer, and dynamic leaching experiment was used to simulate the natural environment. The particle size was used to elucidate the uranium element in the shallow tailings by precipitation leaching, and the kinetic characteristics of the uranium element were investigated. The following conclusion is drawn from the experiment: 1. The effect of particle size on uranium release process in tailings was analyzed. The static immersion and dynamic leaching experiments were carried out on the tailings of a uranium tailings reservoir in southern China. The effects of particle size on the release of uranium elements in different tailings and water coexistence systems were simulated in the reservoir area. The experimental results show that under the condition of static immersion, the uranium release process in uranium tailings of different sizes is similar, the particle size has little effect on the uranium release process in tailings, and the smaller the particle size of tailings is under dynamic leaching conditions, The faster the process of uranium release is, the smaller the particle size of tailings is, the higher the leaching rate of uranium is. However, the smaller the particle size is, the easier it is for the tailings to appear under the condition of static immersion, and the smaller the particle size of tailings is, the smaller the uranium concentration gap is in each stage of the saturated solution, and the more stable the whole uranium release process is. The smaller the fluctuation of uranium concentration, the more favorable for long-term storage. The leaching mechanism and kinetics of uranium in tailings were analyzed. The variation of uranium concentration was simulated and the experimental data were analyzed by finite element regression method. It was pointed out that the kinetic mechanism of uranium release was different in different tailings and water coexistence systems. The simulation results show that the uranyl ions attached to the tailings surface are the main source of the rapid dissolution of uranium elements in the tailings. Under the static immersion conditions, the uranium release in the tailings conforms to the characteristics of the unreacted shrinking nucleus model, and under the dynamic leaching conditions, the uranium release from the tailings conforms to the characteristics of the unreacted shrinking nuclei model. Surface elution is the main form of uranium release from tailings.
【学位授予单位】：南华大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X753

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