Separation of Ruthenium from Simulated Nuclear Waste in Nitric Acid Medium using n-Paraffin Hydrocarbon

Abstract

Ruthenium from pure nitrosyl nitrate solution, nitrate, and from simulated high level liquid waste (SHLLW) in HNO3 medium has been separated by oxidizing with ammonium ceric nitrate (ACN) and trapping the RuO4 vapor in n-paraffin hydrocarbon (NPH). Systematic studies for improving the separation efficiency yielded 80% Ru from nitrosyl nitrate solutions in 1M HNO3, using 0.02–0.04M Ce(IV) as the oxidizing agent at ambient temperature. The optimum process parameters for separating 80–90% Ru from ruthenium nitrate and waste solution (in the form of Ru(NO3)3) were determined to be 0.04M ACN in 4M nitric acid at ambient temperature. The black ruthenium oxide suspension at the interface between the organic and aqueous phases was characterized by EELS and XPS techniques. From the systematic parametric study conducted for the separation of Ru from waste solutions, it is understood that nitric acid concentration in the range 0.5–1M and ACN in the range 0.02–0.04M at ambient temperature are the optimized process parameters for improving the separation efficiency, since in the HLLW, Ru will be in the form of nitrosyl nitrate complexes rather than nitrate solution.