CAS OpenIR
盐湖卤水中铷铯资源的高效分离提取
张建锋
Subtype硕士
Thesis Advisor刘会洲
2018-07
Degree Grantor中国科学院研究生院
Degree Name硕士
Degree Discipline化学工程
Keyword盐湖卤水,铷,铯提取,4-叔丁基-2-(Α-甲苄基)苯酚,T-bambp
Abstract

铷、铯是重要的稀贵资源,盐湖卤水中含有大量的铷离子(Rb+)、铯离子(Cs+),但浓度很低,与其化学性质非常相似的钾离子(K+)浓度却很高,这给Rb+,Cs+的分离提取带来了很大的困难。常用的分离方法有沉淀法、离子交换法和萃取法等。沉淀法成本高、部分工艺过程较为复杂、沉淀物稳定性不高;离子交换法不容易解吸、大部分离子交换剂水力学性能差;而萃取法具有分离效率高、操作简单、易于连续化和放大操作的优点得到了广泛的研究。目前,常用的萃取剂有冠醚类和酚醇类试剂。冠醚类试剂一般用于强酸性的核废料中Cs+的提取,对于中性体系的研究很少;酚醇类试剂一般用于强碱性的溶液体系中,传统的方法是在中性水溶液中加入高浓度氢氧化钠因而容易对环境造成污染,且分离效率较低,工艺成本高。针对于以上问题,开展了盐湖卤水绿色分离提取的新过程研究,研究了不同萃取剂的萃取机理,为盐湖铷铯资源的高效综合利用奠定了基础。首先,针对于杯芳烃冠醚萃取Rb+,Cs+需要强酸性条件的问题,开展了中性萃取体系的研究。以1,3-二异丙氧基杯[4]冠-6(BPC6)为萃取剂,研究了BPC6-正辛醇体系的萃取规律,当水溶液为中性时,对Rb+,Cs+的萃取率仅为20%,加入大量NO3-时萃取率迅速升高后降低,其萃取机理符合中性复合物萃取;当采用BPC6-离子液体(Ionic Liquids,ILs)体系萃取Rb+, Cs+时,萃取规律符合阳离子交换机理,在中性条件下BPC6浓度为12 mmol/L时,99 %以上的Rb+, Cs+ 可被萃取到ILs中,但Cs+/K+ 和Rb+/K+ 的分离系数(βCs/K, βRb/K)不高,同时会造成ILs阳离子损失。另外,针对于4-叔丁基-2-(α-甲苄基)苯酚(t-BAMBP)萃取Rb+,Cs+需要强碱性条件(0.1-1.0 mol/L NaOH)的问题,开展了弱碱性水系萃取新工艺的研究。首先探究了水相中碱度(0-0.1 mol/L NaOH)对萃取的影响,结果表明,碱度越低萃取率越低,但水相中NaOH浓度为0.03 mol/L,2 min时Cs+的萃取率即可达到94.1 %,βCs/K为310.3。在此基础上,提出采用t-BAMBP-十二烷有机相,先用氢氧化钠溶液对有机相进行处理,处理后的有机相可直接用在中性水系中Rb+,Cs+选择性萃取的新操作方式。与传统强碱性萃取工艺相比,新工艺更加绿色环保,不需要调节水相pH达到13以上,可节约70 %-97 %的氢氧化钠,实现了弱碱性体系Rb+,Cs+的提取分离。另外,K+, Rb+, Cs+在被萃取过程中动力学差异变大,因此通过动力学控制的方法使得βCs/K,βRb/K相比传统方法分别增大了71.0和5.8倍。在t-BAMBP体系研究的基础上,开展了含有21.5 mg/L Cs+, 206.7 mg/L Rb+ 和4632 mg/L K+的中性模拟盐湖卤水萃取工艺实验探究。采用3级错流萃取可回收99.1 %的Cs+和86.5 %的Rb+,0.5 mol/L的盐酸即可有效的将Cs+和Rb+反萃下来,萃取剂循环使用5次后性能没有明显下降。这表明新工艺可以用于中性盐湖卤水铷铯资源的高效提取和分离。;Rubidium and cesium are important rare resources. There are plenty of rubidium (Rb+) and cesium ion (Cs+) in the salt lake brine, but the concentrations of them are very low. However, the concentration of K+ is very high and the chemical properties of it are very similar to Rb+ and Cs+. That makes the separation of Rb+ and Cs+ from salt lake brine very difficult. There are three main methods including precipitation, ion exchange and solvent extraction. The disadvantages of precipitation are high cost, complicated processes and low stability of sediment. The disadvantages of ion exchange are hard to desorp and the poor hydrodynamic performance. The extraction method has the advantages of high separation efficiency, simple and easy to continuous operation, which make it widely studied.At present, the commonly used extractants are crown ether species and phenolic alcohol reagents. Crown ether species are generally used for the extraction of Cs+ from strong acidic nuclear waste but the neutral system is hardly investigated. Phenolic alcohol reagents are commonly used in strong alkaline solution and the traditional methods is to add high concentration of sodium hydroxide in neutral aqueous, which could cause serious pollution to the environment and high processing cost. In view of the above problems, a novel process study was carried out on the extraction of Rb+ and Cs+ from salt lake brine. The extraction mechanism of different extraction regents was studied, which laid a foundation for the efficient and comprehensive utilization of rubidium and cesium resources.Firstly, the study of neutral extraction system was carried out for the extraction of Rb+ and Cs+ when the calixarene crown ether was used as extractant. The BPC6-octanol system was studied when 1,3-diisopropyloxycalix[4]crown-6 (BPC6) was used as extractant. When the aqueous solution is neutral, the extraction percentage of Rb+ and Cs+ were only 20%. As the concentration of NO3- increased, the extraction percentage increased first and then decreased. The extraction conformed to the neutral complexes extraction mechanism. When the BPC6-ILs (Ionic Liquids) system was employed, the extraction conformed to the cation exchange mechanism. In neutral aqueous solution, more than 99 % Rb+ and Cs+ could be extracted into ILs phase when concentration of BPC6 was 12 mmol/L. However, the separation factors of Cs+/K+ and Rb+/K+ were moderate and the imidazole cations of ILs were easy to run away.In addition, the study of weakly alkaline system was carried out for the extraction of Rb+ and Cs+ when the 4-tert-butyl-2-(α-methylbenzyl) phenol (t-BAMBP) was used as extractant to overcome the disadvantage of strong alkaline condition (0.1-1.0 mol/L NaOH) being needed. At first, we found that the extraction percentage decreased with the decrease of alkalinity in aqueous solution. However, when the concentration of NaOH in aqueous solution is 0.03 mol/L, the extraction percentage of Cs+ could reach 94.1 % and the βCs/K could reach 310.3. Then, we proposed that t-BAMBP-dodecane was first treated by NaOH solution and then was directly used in neutral water system to extract Rb+ and Cs+ selectively. Compared with the traditional process, the novel process was more environmentally friendly, which could save 70 % to 97 % of NaOH and the alkalinity of raffinate was lower. The kinetics difference K+, Rb+, Cs+ was enlarged in the ion exchange process, so the separation factors of Cs+ over K+ and Rb+ over K+ increased by 71.0 and 5.8 times through controlling the extraction time.Based on the results of t-BAMBP system, the simulated brine solution which contained 21.5 mg/L Cs+, 206.7 mg/L Rb+ and 4632 mg/L K+ was also studied. 99.1 % Cs+ and 86.5 % Rb+ could be recovered through three-stages cross-current extraction. 0.5 mol/L HCl was effective for the stripping of Cs+ and Rb+. There was no significant extraction reduction when the extractant were reused for five times. The novel process showed promising application on the extraction of Cs+ and Rb+ from salt lake brine. 

Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/26851
Collection中国科学院过程工程研究所
研究所(批量导入)
Recommended Citation
GB/T 7714
张建锋. 盐湖卤水中铷铯资源的高效分离提取[D]. 中国科学院研究生院,2018.
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