SEPARATION OF NIOBIUM FROM CHLORIDE MEDIA BY SOLVENT-EXTRACTION WITH DICYCLOHEXYL-18-CROWN-6

Niobium was quantitatively extracted from 7-10 mol dm-3 hydrochloric acid with 2.0 x 10(-2) mol dm-3 dicyclohexyl-18-crown-6 in dichloromethane. The metal was stripped from the organic phase with 0.1 mol dm-3 sulphuric acid and determined spectrophotometrically at 540 nm as its complex with 4-(2-thiazolylazo)resorcinol. This method permits the sequential separation of niobium from vanadium, tantalum, zirconium, hafnium and iron