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A process is set up to treat ammonium nitrate wastewaters. It couples membrane electrolysis and electrodialysis. Membrane electrolysis regenerates nitric acid and ammonia while electrodialysis is suitable to extract a depleted stream from the salt circuit and to recycle a concentrated stream. The membrane electrolysis current efficiency of acid production decreases when acid concentration in the anolyte increases and does not depend on the ammonium nitrate concentration in the tested range (0.25–2.5 mol L-1). The average value is about 58% when acid concentration runs from 1 to 8 mol L–1. Ammonia is stripped in situ in order to avoid loss of efficiency due to its back-diffusion. The ammonia efficiency values obtained are higher than those for acid production (between 70 and 85%). Electrodialysis produces a depleted stream containing less than 3.5 10–3 mol L–1 and a concentrated stream containing more than 2 mol L–1 of ammonium nitrate. This is achieved with 95% current efficiency. An example of process design is given.

A process to treat ammonium nitrate wastewaters, like those produced in the processing of uranium is designed. The main operation is membrane electrolysis, which regenerates nitric acid and ammonia. Concentrated nitric acid, up to 8 mol L–1, may be produced with a good current efficiency. Ammonia stripping is performed in situ. D. Pletcher and F.C. Walsh, Industrial Electrochemistry, Chapman & Hall, Glasgow, 2nd ed., 1990, 654 p. [2] H.S. Burney, Membrane Chlor-Alkali Process, in: Modern Aspects of Electrochemistry, R.E. White, B.E. Conway and J.O’M. Bockris, (Eds.), Plenum Press, New York, 24 (1993) 393–437. [3] S. Cattoir, D. Smets and A. Rahier, The use of electroelectrodialysis for the removal of sulphuric acid from decontamination effluents, Desalination, 121 (1999) 123– 130. [4] M. Rakib, Ph. Moçotéguy, Ph. Viers, E. Petit and G. Durand, Behavior of Nafion 350 membrane in sodium sulfate electrochemical splitting: continuous process modeling and pilot scale tests, J. Appl. Electrochem., 29 (1999) 1439– 1448. [5] G.S. Luo and F.Y. Wu, Concentration of formic acid solution by electro-electrodialysis, Sep. Sci. Technol., 35 (2000) 2485–2496. [6] S. Mazrou, H. Kerdjoudj and A.T. Cherif, Sodium hydroxide and hydrochloric acid generation from sodium chloride and rock salt by electro-electrodialysis, J. Appl. Electrochem., 27 (1997) 558–567. [7] T. Sawa, Y. Hirose, Y. Ishii, A. Takatsudo, K. Wakasugi and H. Hayashi, Development of electrochemical denitrification from waste water containing ammonium nitrate, I.C.E.M Conference Proc., 2 (1995) 1089–1093. [8] T. Sawa, Y. Hirose and Y. Ishii, Development of treatment system of waste water containing NH4NO3 by application of electrochemical process, Soda to enso, 49 (1998) 248– 257. [9] Y. Lorrain, G. Pourcelly and C. Gavach, Influence of cations on the proton leakage through anion-exchange membranes, J. Membr. Sci., 110 (1996) 181–190. [10] B.J. Robbins, R.W. Field, S.T. Kolaczkowski and A.D. Lockett, Rationalization of the relationship between proton leakage and water flux through anion-exchange membranes, J. Membr. Sci., 118 (1996) 101–110.