Where is the Anion Extraction Going?

TLDR

Reactive extraction is widely used for metal ions, yet anion extraction is comparatively rare and largely depends on nonspecific ion‑pairing with hydrophobic ammonium cations, motivating new strategies that combine biological insights and supramolecular chemistry for selective anion binding and transport. This review seeks to evaluate current research trends and application prospects of novel extractant types for the separation and concentration of anionic species. The authors accomplish this by surveying recent literature on emerging extractant designs and their performance in anion extraction.

Abstract

Abstract Reactive extraction processes represent efficient and smart technologies for separation and concentration of metal ions in solution, which are frequently used in industry. Despite the importance of anions in biology, medicine, environment and industry, practical examples of anion extraction are relatively limited compared to metal ion separation. Anion extraction processes are mainly based on the nonspecific ion pair formation with hydrophobic ammonium cations. In this case the phase transfer of anions is dominated by their lipophilicity. The reasons for this situation are closely connected with the specific features of anions in contrast to cations. Novel approaches for specific binding and selective transport of anionic components are based both on the better understanding of the biological role of anions and on the possibilities of supramolecular chemistry to create receptor architectures with complementary binding modes for anions. In the given review the authors discuss present research tendencies and application possibilities of new extractant types for separation and concentration of anionic species in solution.