An amide functionalized calix-benzocrown-6 ionophore for the selective extraction of cesium from highly concentrated nitric acid: the effect of intramolecular buffering

A series of novel calix[4]arene-benzocrown-6 amide (CBCA) ligands in 1,3-alternate conformation having an amide group attached to the aromatic ring of the polyether ring network have been synthesized and evaluated for the extraction of cesium at varying concentrations of aqueous nitric acid. Amide substituted calix-crowns modified with isodecyl alcohol (IDA) and o-nitrophenylhexyl ether (o-NPHE) in n-dodecane have been used for the extraction of cesium and compared to their non-amide analogue viz. calix-benzocrown (CBC). It was observed that the presence of the amide group enhanced the uptake of cesium at high nitric acid concentrations as compared to CBC. This behavior may be attributed to an internal buffering effect of the amide group present in the calix-crowns.