SOLVENT EXTRACTION OF PERTECHNETATE AND PERRHENATE IONS FROM NITRATE-RICH ACIDIC AND ALKALINE AQUEOUS SOLUTIONS

Abstract

ABSTRACT Solvent extraction studies of 99TcO4 − and its nonradioactive congener ReO4 − into 1,3-diisopropylbenzene and several other organic solvents containing the 0.200 M Aliquat-336 nitrate (which is predominantly methyltrioctylammonium nitrate) from a variety of aqueous solutions led to the following conclusions: (i) ReO4 − is a suitable solvent extraction surrogate for 99TcO4 − under conditions that model nuclear waste streams at the DOE Hanford site; (ii) distribution ratios (D values) greater than 100 can be achieved for TcO4 − extraction from aqueous solutions containing a mixture of 1 M NaOH and 1.5 M NaNO; (iii) the addition of 1.5 M NaNO2 or 0.14 M K2CrO4 to the aqueous phase containing a mixture of 1 M NaOH and 1.5 M NaNO3 does not significantly affect D(TcO4 −); (iv) D(TcO4 −) values were larger by a factor of 3-5 when ketone solvents with flash points above 60°C were substituted for 1,3-diisopropylbenzene. Initial and final concentrations of TcO4 −- in the organic and aqueous phases were determined by γ counting of solutions of 99TcO4 − that contained tracer amounts of 95mTcO4 −(0.204 MeV). Initial and final concentrations of ReO4 − in the aqueous phase were determined by ICP-AES.