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Simultaneous Determination of Uranium,Nitric Acid and Nitrous Acid by Direct Spectrophotometry

A second-order derivative spectrophotometric method for simultaneous determination of uranium,nitric acid,and nitrous acid in Purex process was developed.The molar absorbance matrix was calibrated with absorbance data measured in the wavelength range 350-500 nm for a series of standard solutions by linear least-squares regression.This method uses the information from the absorption spectra of U(Ⅵ)-nitrous acid-nitric acid solutions to determine U(Ⅵ),nitrous acid,and nitric acid.In the ranges of 0.95-74.1 g/L U(Ⅵ),5×10-4-2×10-3 mol/L nitrous acid and 3-5 mol/L nitric acid aqueous solution,the measuring precision for determination of U(Ⅵ),nitric acid,and nitrous acid are 0.46%,0.68%,4.09% respectively.In the solution of 30%TBP-kerosene,the measuring precision for determination of U(Ⅵ) and nitrous acid are 0.42% and 4.2% respectively in the ranges of 0.95-74.1 g/L U(Ⅵ) and 5×10-4-2×10-3 mol/L nitrous acid.The spectrophotometric method could be valuable for monitoring and controlling of both species in Purex process operation,thanks to its simpleness,quickness and trueness.