ИСТИНА

One of the main applications of coordination compounds is their use in processes of extraction, separation and concentration of various metal ions from complex solutions. Traditionally two main approaches were employed – liquid extraction and sorption, the first being dominating for several decades. The modern trend in hydrometallurgy is widespread replacement of liquid extraction by sorption processes, which are more effective, universal and eco-friendly. In this report we analyze the achievements in the sorption separation within two groups of elements possessing very similar properties – platinum metals and rare earths. Coordination chemistry forms the basis for technologies discussed. Firstly, the effectivity and selectivity of metal ions sorption by modern sorbents are provided by the use of specific ligands which are chemically attached to solid support. Among these ligands, a special attention is paid to various macrocycles whose application leads to so-called molecular recognition technologies. Secondly, the selectivity of sorption can be regulated by complex formation of metal ions in liquid phase. For example, the addition of complexing ligands, namely, hydroxyl or amino acids, to solution plays significant role in separations of rare earth elements. Complex forming agents are used also for elution of sorbed ions, which is a crucial stage in the separation of platinum metals. By now numerous sorbents with attached organic ligands are synthesized and tested. In this report we make an emphasis on silica based sorbents which are widely used in analysis, as well as in some industrial processes. The advantages and limitations of these sorbents are discussed. Some examples of industrial processes of platinum metals and rare earth elements separation are presented.