Study of extraction by tri-n-octylamine of mixed niobium (5) and tantalum (5) complexes with 4-(2-pyridylazo)resorcinol and hydroxy acids

Using the spectrophotometric method, the extraction of mixed complexes of niobium (5) and tantalum (5) with 4-(2-pyridylazo)-resorcinol (PAR) and hydroxy acids by chloroform solutions of tri-n-octylamine (TOA) is studied. An increase in the number of free hydroxy groups in secondary ligand molecule results in the decrease of the compound extractivity. Mixed complexes Nb(5)-PAR-oxalate, Nb(5)-PAR-tartrate, TA(5)-PAR-oxalate are extracted by TOA solutions. From citrate (the complex Nb(5)-PAR-citrate is extracted non-quantitatively) to trihydroxygltarate and mucinate, used as secondary ligands, mixed complexes are formed, which practically can not be extracted by TOA. Extraction mechanism of anion mixed complexes of Nb(5) and Ta(5), formed in aqueous phase, is discussed