Macrocycle carriers for separation of metal ions in liquid membrane processes—a review Original Research Article

A review with more than 60 references covering macrocycle and macromolecular compounds, i.e. crown ethers, ionizable lariat ethers, calixarenes, calix crowns, as well as macrocycle polymers (for example, cyclodextrins), and macromolecular compounds, i.e. acyclic polyethers used as ion carriers in transport across liquid membranes for metal ions selective removal will be presented. The recent literature data as well as our own research results (published in the last 8 years) on metal ions removal and separation will be summarized. Recent developments of the lariat ethers application as ion carriers for alkali metal and alkaline earth metal cations, as well as heavy metal ions removal and separation will be presented in this review. The effect of structural studies of crown ring size variation, lipophilic and acidic group attachments for lariat ethers with carboxylic and other acidic groups on the selectivity and efficiency of metal cations transport will also be presented. Also, the effect of a counter anion presence will be performed. The examples of metal ions selective removal using various other ion carriers such as calixarenes, calixcrown ethers, cyclodextrins and their polymers as well as acyclic polyethers will also be shown.