溶浸采铀过程中铁的不同形态化合物对铀的吸附机理研究

发布时间：2018-03-08 12:32

本文选题：Fe(OH)3胶体　切入点：水合氧化铁　出处：《南华大学》2015年硕士论文　论文类型：学位论文

【摘要】：溶浸采铀工艺目前通常采用过氧化氢、氧气等做氧化剂,氧化剂首先将溶液中的Fe2+氧化为Fe3+,再由Fe3+氧化U4+为UO22+。由此可见,铁的行为在溶浸采铀中起着重要作用。铁在溶浸采铀中充当氧化剂的同时,还会与溶浸剂(无论是酸性、碱性、中性)发生化学反应,并在一定的温度与压力作用下,生成含铁元素的化合物,经过分析,主要为Fe(OH)3胶体和水合氧化铁。含铁化合物可能对铀矿物产生包裹,影响溶浸液与矿物界面的接触和反应,影响铀的浸出速度和浸出率。同时,可能附着在矿石表面,影响铀的浸出和矿层渗透性。本文在实验室条件下模拟制备了Fe(OH)3胶体和水合氧化铁,研究其对铀的吸附机理,主要研究内容和成果如下:(1)在混合溶剂中模拟制备得到氢氧化铁胶体,进行铀酰离子吸附实验,研究了p H值、初始铀浓度及吸附时间等对Fe(OH)3胶体吸附铀的影响。采用准一级、复合二级与Elovich动力学模型对数据进行了动力学计算与分析,结果表明Elovich动力学方程更适合描述Fe(OH)3胶体对铀的吸附行为;采用Freundlich与Langmuir等温吸附方程对实验数据进行了热力学分析和拟合,结果表明Freundlich模型更适合描述Fe(OH)3胶体对铀的吸附行为。综合两种模型的结论推测,推测Fe(OH)3胶体对铀的吸附属于不均匀表面的单层物理吸附。根据激光粒度分析与SEM图分析结果,推测Fe(OH)3胶体对铀具有较强的吸附性能,吸附主要是表面吸附。(2)以Fe SO4·7H2O为主要原料模拟制备水合氧化铁,进行了铀酰离子吸附实验,得出在p H=5时,水合氧化铁的吸附作用发挥到最大。在吸附一小时内,水合氧化铁对铀具有很高的吸附速率,并在5小时后达到吸附平衡。对吸附行为进行动力学拟合,发现准二级动力学方程最适合用来描述铀在水合氧化铁上的吸附行为,拟合相关系数R2为0.994,推算平衡吸附量为55.40 mg·g-1与实验数据52.78 mg·g-1相吻合。(3)探究了Fe(OH)3胶体与水合氧化铁协同吸附铀的效果,结果表明:氢氧化铁胶体与水合氧化铁单独作为吸附剂时,吸附效果良好;但随着复合比的增加,两者之间的相互干扰作用就越明显,吸附量会随着复合比的增加而减少。
[Abstract]:At present, hydrogen peroxide and oxygen are usually used as oxidants to oxidize Fe2 in solution to Fe3 and then U4 to UO22 by Fe3. The behavior of iron plays an important role in the leaching of uranium. When iron acts as an oxidant in leaching uranium, it also reacts with the leaching agent (acid, alkaline, neutral) and acts at a certain temperature and pressure. The formation of iron-containing compounds is mainly composed of Fe(OH)3 colloid and hydrated ferric oxide. The iron-containing compounds may encapsulate uranium minerals and affect the contact and reaction between leaching solution and mineral interface. The leaching rate and leaching rate of uranium are affected. At the same time, it may be attached to the surface of ore, which may affect the leaching of uranium and the permeability of ore bed. In this paper, Fe(OH)3 colloid and ferric oxide hydrate were prepared under laboratory conditions, and the adsorption mechanism of uranium was studied. The main contents and results are as follows: (1) Ferric hydroxide colloid was prepared in mixed solvent. The adsorption experiments of uranyl ions were carried out. The effects of pH value, initial uranium concentration and adsorption time on the adsorption of uranium by Fe(OH)3 colloid were studied. The complex second-order and Elovich kinetic models were used to calculate and analyze the data. The results show that the Elovich kinetic equation is more suitable to describe the adsorption behavior of uranium by Fe(OH)3 colloid. The thermodynamic analysis and fitting of the experimental data with Freundlich and Langmuir isotherm adsorption equations are carried out. The results show that the Freundlich model is more suitable for describing the adsorption behavior of uranium by Fe(OH)3 colloids. It is inferred that the adsorption of uranium by Fe(OH)3 colloid is a single layer physical adsorption on heterogeneous surface. According to the results of laser particle size analysis and SEM diagram analysis, it is inferred that Fe(OH)3 colloid has strong adsorption property for uranium. Fe SO4 路7H 2O was used as the main raw material to simulate the preparation of hydrous iron oxide. The uranium ion adsorption experiments were carried out. The results showed that the adsorption of hydrated iron oxide reached its maximum at 5:00, and within one hour of adsorption, The adsorption rate of uranium is very high and the adsorption equilibrium is reached after 5 hours. The kinetic fitting of the adsorption behavior shows that the quasi-second-order kinetic equation is the most suitable for describing the adsorption behavior of uranium on the hydrated iron oxide. The correlation coefficient R2 was 0.994, and the calculated equilibrium adsorption capacity of 55.40 mg 路g -1 coincided with the experimental data of 52.78 mg 路g -1. The effect of Fe(OH)3 colloid on synergistic adsorption of uranium with hydrated ferric oxide was investigated. The results showed that when the colloid of ferric hydroxide and ferric hydroxide were used as adsorbents alone, The adsorption effect is good, but with the increase of the composite ratio, the interaction between the two is more obvious, and the adsorption amount will decrease with the increase of the composite ratio.
【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】：TD868

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