Kinetics of nitrous acid formation in a two-phase tri-n-butylphosphate-diluent/aqueous nitric acid extraction system under the effect of power ultrasound

The kinetics of nitrous acid formation were investigated in two-phase tri-n -butylphosphate (TBP)-diluent/HNO3 (1.5-6.0 mol 1(-1)) systems, where dilue nt is n-C16H34, n-C12H26 n-C9H20 and i-C8H18, under the effect of power ult rasound at 20 kHz frequency under Ar atmosphere. The rate of HNO2 sonochemi cal formation decreases with the rise in diluent vapor pressure. The HNO2 f ormed is distributed between the aqueous and organic phases due to its extr action with TBP. The kinetics of HNO2 sonochemical formation in the two-pha se system exhibits induction periods due to NOx (NO + NO2) gas reactions in the HNO3 medium. This induction period decreases with increasing HNO3 conc entration and ultrasound intensity. The HNO2 steady-state concentration was obtained under long-time sonication as the result of HNO2 sonochemical dec omposition. HNO2 decomposes faster under sonication in the aqueous phase th an in the organic phase. (C) 2000 Elsevier Science B.V. All rights reserved .