Coupling of bipolar membrane electrodialysis and ammonia stripping for direct treatment of wastewaters containing ammonium nitrate

Splitting of ammonium nitrate to nitric acid and ammonia was achieved by a coupled process including bipolar membrane electrodialysis and in situ ammonia stripping. The effect of homopolar ion-exchange membranes on current efficiency led to the selection of AW (Solvay) and CMB (Tokuyama Soda) membranes. The main parameters influencing the current efficiency were acid and ammonia concentrations. Proton leakage through the anion-exchange membrane is proportional to acid concentration. Ammonia diffuses through the membranes independently of the current. Higher current efficiency was obtained at higher current density. Batch and continuous processing were compared.