Decomposition of nitrite under various pH and aeration conditions

Studies on the decomposition/oxidation of nitrite at different pH values and aeration flow rates were investigated using a bench-scale batch reactor. The conditions were pH 2.85, 3.50, 5.80, 7.0, and 11.6, and with or without aeration at airflow rates of 1.50, 2.25, and 3.25 L min(-1). Decomposition/oxidation of nitrite may be described by a pseudo-first order expression, and the rate constants for nitrite decomposition/oxidation ranged from 1.2 x 10(-6) s(-1) to 1.12 x 10(-4) s(-1) depending on the experimental conditions. The rate of decomposition/oxidation of nitrite was found to increase for low pH conditions and for high airflow rates. The experimental results showed that the dominant reaction in the decomposition/oxidation of nitrite in low pH solutions and in the presence of some aeration was most probably the decomposition of nitrous acid to NO and NO2. Oxidation of nitrite to nitrate appeared to proceed in a smaller proportion in comparison to the breakdown of nitrous acid to nitrogen oxide compounds. Results from this study showed that emissions of nitrogen oxides from nitrite-containing solutions are possible if the solutions were agitated and the pHs of the solutions were less than 6.