摘要
稀土作为重要的战略资源,在国防、航天、永磁材料、新能源汽车、发光材料等领域应用十分广泛,各个领域对单一稀土纯度的要求越来越高,因此,高效的分离技术成为稀土应用的关键。溶剂法作为最重要的分离稀土方法,在实际生产应用中被广泛研究。随着绿色环保意识的增强,原始萃取分离稀土的工艺弊端越发明显,开发绿色高效的萃取体系和工艺显得至关重要。文章综述了溶剂法萃取分离稀土的现状,根据溶剂性质的差异以及萃取体系的不同分别从不同角度对溶剂法进行了阐述。详细介绍了中性萃取剂、酸性萃取剂、胺类萃取剂以及离子液体萃取剂在稀土萃取中的应用情况,并根据萃取效果分析其在萃取应用中存在的优点和不足。同时阐述了协同萃取体系和络合萃取体系的研究和应用情况,相较于单一萃取剂有更明显优势。在此基础上,展望了未来溶剂法萃取分离稀土的发展方向,为更好地综合利用稀土资源提供借鉴。
As an important strategic resource,rare earth was widely used in the fields of national defense,aerospace,permanent magnet materials,new energy vehicles,luminescent materials,etc.,and the requirements for the purity of a single rare earth in various fields were getting higher and higher. Therefore,efficient separation technology became the key to rare earth applications. Solvent method,as the most important method for separating rare earths,had been widely studied in practical production applications. At present,organic extractants could be divided into neutral extractants,acidic extractants,alkaline extractants and ionic liquid extractants according to the difference in their properties. Among them,neutral extractants generally included oxygen-containing extractants(lipids,ketones,etc.),phosphine-containing extractants(phosphonates,phosphine oxides,etc.),nitrogen-containing extractants(substituted amides)and sulfur-containing extractants(sulfoxides,sulfides). This type of extractant was used in industrial rare earth extraction due to its advantages of easy stripping and stable extraction,but there were also problems such as easy emulsification and degradation,and the extraction mechanism of rare earth was more complicated. In addition to the neutral coordination mechanism,the agent also had a hydrated cation coordination mechanism,which increased the difficulty of controlling the extraction conditions. Acidic extractants generally included phosphonic acids,carboxylic acids,chelates,etc. This type of extractant had the advantages of good separation effect on rare earth elements,large saturation capacity and strong pertinence,but there were also problems such as difficulty in stripping,easy emulsification,and production of ammonia nitrogen wastewater and damage to the environment,which restricted the development and application of phosphonic acid extractants. Amines compared with acidic extractants,although they had the advantages of large extraction capacity,strong selectivity and good stability,the overall separation effect was lower than that of acidic extractants. More stages were required to achieve rare earth separation,which reduced production efficiency;compared with other traditional extractants,ionic liquid extractants had the advantages of low volatility and stability,strong stability,low toxicity,large adsorption capacity,high designability,and easy circulation. Taking advantage of such advantages,it had good application potential in the field of rare earth extraction and separation. However,during the extraction process,the ionic liquid would enter the solution in the form of ions,causing the loss of the ionic liquid and increasing the production cost. At present,it was still only in the laboratory research stage. With the increasing awareness of green environmental protection,the disadvantages of the original single extraction system for separating rare earths became more and more obvious,and it was very important to develop a green and efficient extraction system and process. The research and application of synergistic extraction system and complex extraction system were expounded. Among them,two or more extraction agents were combined to form a multi-element extraction system,and combined with the advantages of each extraction agent,it could often show higher extraction rate and selectivity,increase the stability of the extract,and improve the organic extraction agent. However,there were still unsolved problems in the synergistic extraction extractant system. For example,when the extractant was recovered during the synergistic extraction process,the molar ratio of the extractant changed due to the difference in solubility and recovery effect. Direct circulation was not conducive to medium and long-term stable operation of the industry. At the same time,the root cause of the synergistic effect had not been discovered,and theoretical research needed to be further developed. The complexation extraction system was mainly to add a certain complexing agent to the extraction system to inhibit or promote the extraction complexation to achieve the purpose of improving the separation effect. Generally,the addition of complexing agents could better promote the extraction and separation of rare earths. In addition,it was basically non-toxic,environmentally friendly,and had the advantages of high reaction efficiency and good selectivity,which made the screening and application of complexing agents very meaningful. However,after the complexing agent was added into the extraction system,it was difficult to be effectively recycled,which was also the main reason for restricting the application of complexing agent in industry. The development of science and technology had higher and higher requirements for the purity of rare earths,and the research on the extraction and separation of rare earths had been widely carried out at home and abroad. In the process of continuous development in recent decades,the solvent method had been continuously improved and innovated as the most important method of current industrial production,and the limitations of other types of extraction methods had also been continuously overcome,jointly promoting the development of green technology for rare earth extraction and separation. Although many studies were still in the stage of laboratory research and application,this also laid a theoretical foundation for industrial production and application,and contributed to the better utilization of rare earth resources.
作者
张文杰
童雄
杜云鹏
曹阳
封东霞
谢贤
Zhang Wenjie;Tong Xiong;Du Yunpeng;CaoYang;Feng Dongxia;Xie Xian(Faculty of Land and Resources Engineering,Kunming University of Science and Technology,Kunming 650093,China;Yunnan Metal Tailings Resource Utilization Engineering Research Center,Kunming 650093,China)
出处
《稀有金属》
EI
CAS
CSCD
北大核心
2022年第12期1645-1656,共12页
Chinese Journal of Rare Metals
基金
国家自然科学基金项目(U1802252)资助。
关键词
稀土
溶剂法
萃取
萃取体系
分离
rare earths
solvent method
extraction
extraction system
separation
