Recovery and reuse of nitric acid from effluents containing free nitric acid in absence and presence of metal nitrates

Nitric acid is a commonly used dissolving agent in nuclear, chemical and metallurgical industries. All these industries generate and discharge a huge quantity of effluents containing free nitric acid and different metal nitrates. Disposal of effluents containing high nitrate concentration is a serious and global problem. Nitrate contamination in drinking water causes methemoglobinemia, a disease in which oxygen-bearing capacity of blood is reduced, which is called Blue-Baby-Syndrome. It is possible to recover and reuse nitric acid from effluents containing free nitric acid and which is the novelty of the present work. Experiments were carried out to recover nitric acid from aqueous solution containing nitric acid in absence and presence of different metal ions viz., Na+, Mg+2, Ca+2 and Al+3 by solvent extraction. Tributyl phosphate (TBP) was selected among several extractant because of its better selectivity towards nitric acid (HNO3), overall superiority in operation, favourable physical properties and economics. The experimental details and results are discussed in this paper.