SBA-15-PVC膜型吸附剂的制备及其对铀的吸附性能研究

发布时间：2018-01-31 03:22

本文关键词： SBA-15 长孔道短孔道 PVC膜铀吸附　出处：《中国海洋大学》2015年硕士论文　论文类型：学位论文

【摘要】：随着现代工业的迅速发展,能源问题日益突出。铀作为新能源核能的一种重要原料,被认为是最有发展前景的战略能源。然而陆地铀矿资源有限且面临着过度开采。而海水中铀总量达到45亿吨,约为陆地储量的1000倍,因此从海水中提取铀具有重要的战略意义。但是海水中铀的浓度很低,只有3.3μg/L,因此其分离和提取技术显得尤为重要。近年来,多种方法被应用于铀的提取,如离子交换、吸附、溶剂萃取、化学沉淀、超滤、纳滤以及反渗透等。吸附法由于经济高效、环境友好、操作简单等优点,成为从海水中提取铀的主要方法,因此寻找一种合适的吸附剂是研究的关键。近年来介孔二氧化硅作为一种新兴的无机材料逐渐吸引了人们的注意,因为其具有高比表面积、均匀有序的介孔孔道、较大的孔体积、形貌和结构组成可控、孔径可调、表面富含羟基等优点。与其他介孔材料相比,SBA-15囚具有较大孔径、较厚的孔壁及更高的水热稳定性而表现出更加优异的性能。传统方法制备的SBA-15孔道走向平行于长轴,不利于孔道内能量传递以及物料传输,并且易引起孔的堵塞。相比之下,具有短孔道的SBA-15因孔道走向平行于短轴而利于物质运输和能量传递,应用前景广阔。然而无论是纯二氧化硅基SBA-15还是功能化的SBA-15均为粉末状使其具有不易操作及难回收重复利用等不足,难以被应用于工业化操作及商业领域。因此,本论文将粉末状吸附剂添加到铸膜液中制备膜型吸附剂,因为膜可以进行弯曲或缠绕等操作,适用于工业化应用,因此可以克服粉末状吸附剂的不足。首先,以水热法合成了长孔道SBA-15(L-SBA-15),将其添加到PVC铸膜液中,通过相转化法制备了L-SB A-15-PVC膜型吸附剂。实验结果表明,在PVC浓度为10%、L-SBA-15含量为5%、溶液pH=6的条件下,L-SBA-15-PVC膜的吸附容量为2014.0 mg/m2。其吸附行为符合准二级动力学模型与Langmuir吸附等温模型,其经3mol/L硝酸脱附后的循环吸附效果良好,吸附量几乎没有损失。对比了粉末状L-SBA-15对铀的吸附性能,发现成膜后的L-SBA-15的吸附容量仅损失了10.9%,但吸附及脱附的操作步骤大为简化且易于重复利用。其次,合成了短孔道SBA-15(S-SBA-15),并将其添加到铸膜液中制备S-SBA-15-PVC膜型吸附剂。结果表明,在PVC浓度为10%、S-SBA-15含量为5%、溶液pH=6的条件下,S-SBA-15-PVC膜的吸附容量可达2520.0 mg/m2,明显高于L-SBA-15-PVC膜型吸附剂。以Langmuir和Freundlich两种等温吸附模型拟合吸附过程,结果表明铀离子在S-SBA-15-PVC膜型吸附剂上的吸附过程更符合Langmuir吸附等温模型。动力学研究表明S-SBA-15-PVC膜对铀的吸附过程用准二级动力学模型描述更为合适。进行了九次吸附-解吸实验,在后八次循环中吸附量几乎保持不变。最后,将SBA-15进行有机官能化改性,制备了氰基和偕胺肟基功能化的SBA-15,然后将其添加到PVC铸膜液中,制备成膜型吸附剂并考察其对溶液中铀的吸附效果。实验结果表明,改性后的SBA-15-PVC膜吸附容量明显优于未经改性的SBA-15-PVC膜。通过该方法制备的膜型吸附剂的性能与相应的粉末吸附剂呈正相关,说明该制膜工艺比较成熟,吸附剂本身的性能决定了成膜后的吸附效果。因此,寻找吸附性能更加优异的吸附剂将是后续研究的重点。
[Abstract]:With the rapid development of modern industry, energy issues become increasingly prominent. Uranium as an important raw material of new nuclear energy, is considered to be the most promising energy strategy. However, land limited uranium resources and facing excessive exploitation. The uranium from seawater volume reached 45 tons, about 1000 times the land reserves, so the extraction uranium has an important strategic significance from the sea. But the concentration of uranium in sea water is very low, only 3.3 g/L, so the separation and extraction technology is particularly important. In recent years, many methods have been applied to the extraction of uranium, such as ion exchange, adsorption, solvent extraction, chemical precipitation, ultrafiltration, nanofiltration and reverse infiltration. Adsorption due to the economic efficiency, environmental friendly, simple operation and other advantages, has become the main method of extracting uranium from sea water, so to find a suitable adsorbent is the key of the study. In recent years, mesoporous silica as a The new inorganic materials gradually attracted people's attention, because of its high specific surface area, pore size uniform and orderly, larger pore volume, morphology and structure controllable, adjustable pore size, surface hydroxyl rich advantages. Compared with other mesoporous materials, SBA-15 cell with large pore size, thick pore wall and higher hydrothermal stability and exhibit more excellent properties. The preparation of SBA-15 channel to parallel to the long axis of the traditional method, is not conducive to energy transfer channels and material transport, and easy to cause pore blockage. Compared with SBA-15 for short channel channel to parallel to the short axis for material transport energy transfer and wide application prospect. However, whether it is a pure silica based SBA-15 or functionalized SBA-15 were powder which is not easy to operate and difficult to recycle lack of reuse, it is difficult to be used in the industry Operation and business. Therefore, this paper will be added to the powder adsorbent in the casting solution preparation of membrane type adsorbents, because of bending or winding operation can be applied to film, industrial application, so it can overcome the shortage of powdered adsorbent. Firstly, by hydrothermal method with a long channel SBA-15 (L-SBA-15), PVC will be added to the casting solution, prepared by the method of phase inversion L-SB A-15-PVC membrane adsorbent. The experimental results show that the concentration of PVC was 10%, L-SBA-15 was 5%, pH=6 of the solution under the condition that the adsorption capacity of L-SBA-15-PVC film with quasi two level dynamic model and Langmuir adsorption isotherm the model is 2014 mg/m2. the adsorption behavior, the nitrate desorbed by 3mol/L cyclic adsorption effect is good, the adsorption capacity is almost no loss. The adsorption properties of L-SBA-15 powder of uranium by comparison, found that the adsorption capacity of the film L-SBA-15 only lost 10.9%, but the adsorption and removal steps of greatly simplified and easy to reuse. Secondly, the short channel SBA-15 synthesis (S-SBA-15), and add it to the casting solution preparation of S-SBA-15-PVC membrane type adsorbents. The results showed that the concentration of PVC was 10%, S-SBA-15 was 5%, pH =6 solution under the condition that the adsorption capacity of S-SBA-15-PVC film is 2520 mg/m2, significantly higher than that of L-SBA-15-PVC membrane adsorbent. The adsorption process using Langmuir and Freundlich model to fit the adsorption of two kinds of isothermal, the results show that the adsorption process of uranium ions in S-SBA-15-PVC membrane adsorbent conforms to Langmuir adsorption isotherm model. Kinetic studies showed that the adsorption process of S-SBA-15-PVC films on uranium with the quasi two level dynamic model description is more appropriate. The nine adsorption desorption experiment, adsorption capacity after eight cycles remains almost unchanged. Finally, the SBA-15 of organic functional modification, preparation Cyano and amidoxime functionalized SBA-15 were prepared, and then add it to the PVC casting solution, preparation of membrane adsorbents and study the adsorption of uranium. The experimental results show that the adsorption capacity of modified SBA-15-PVC membrane was obviously better than that without SBA-15-PVC film modified by the. The preparation methods of the properties of membrane type adsorbents and the corresponding powder adsorbent was positively related to the membrane preparation process is relatively mature, the performance of adsorption agent itself determines the adsorption effect of the film. Therefore, looking for more excellent adsorption properties will be the focus of future studies.

【学位授予单位】：中国海洋大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O647.33

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