Extraction of am(vi) from nitric acid solution containing phosphate anion by tbp

Abstract

The extraction behavior of Am(VI) was studied for a nitric acid solution containing ammonium dihydrogenphosphate using tri-n-butylphosphate (TBP) and other extractants. TBP and HDEHP solutions diluted with n-dodecane do not reduce Am(VI) in the extraction procedure, whereas CMPO and TOA do. In TBP extraction, phosphate anion raises the separation factor of Am from Nd as high as 120 with 1 MTBP solvent from 3 M HNO3-1 M NH4H2PO4, although it suppresses the extraction of both. A distribution ratio value of 6.6 was obtained using undiluted TBP. Dissociated phosphate anion H2PO4 forms a complex that lowers the distribution ratio of Am even in highly concentrated nitrate solution at low acidity. Americium(VI) is extracted as AmO2(NO3)2.2 TBP. The stability constant, log β, for Am(VI)- H2PO4 complex was estimated as 1.2. © 2002 Atomic Energy Society of Japan.