Equilibrium Study for the System Tri-n-butyl Phosphate, Normal Paraffin Hydrocarbon, and Nitric Acid

Tri- n -butyl phosphate (TBP) in diluent is generally used as a solvent for the extraction of fissile materials in the reprocessing of spent fuels by the PUREX process. The mutual solubility of TBP and water leads to the transfer of some finite amount of TBP into the aqueous phase. The distribution study of TBP between normal paraffin hydrocarbon (NPH) and nitric acid has been studied. Equilibrium curves have been generated for TBP in different concentrations of nitric acid and NPH. The distribution coefficient ( K d ) is also calculated by measuring the concentration of associated TBP in the aqueous and organic phase. The effect of an inert diluent on the solubility of TBP in nitric acid is also studied. It has been found that the distribution coefficient value varies with the concentration of TBP, nitric acid, and NPH. Nitric acid partitioning between TBP and water has also been studied. The concentration of nitric acid in both phases was determined by the titration method. It has also been proven that the concentration of nitric acid varies during this equilibrium study due to 1:1 complex formation with TBP by hydrogen bonding. The equilibrium study of this TBP-NPH-nitric acid system will aid in finding out the amount of TBP in different concentrations of nitric acid in the presence of a diluent. This study will be useful in nuclear waste management generated by spent fuels of reprocessing origin.