A Novel Method Based on Hydrodynamic Cavitation for Improving Nitric Oxide Removal Performance of NaClO₂

In the removal of nitric oxide (NO) by sodium chlorite (NaClO₂), the NaClO₂ concentration is usually increased, and an alkaline absorbent is added to improve the NO removal efficiency. However, this increases the cost of denitrification. This study is the first to use hydrodynamic cavitation (HC) combined with NaClO₂ for wet denitrification. Under optimal experimental conditions, when 3.0 L of NaClO₂ with a concentration of 1.00 mmol/L was used to treat NO (concentration: 1000 ppmv and flow rate: 1.0 L/min), 100% of nitrogen oxides (NO_x) could be removed in 8.22 min. Furthermore, the NO removal efficiency remained at 100% over the next 6.92 min. Furthermore, the formation of ClO₂ by NaClO₂ is affected by pH. The initial NO_x removal efficiency was 84.8-54.8% for initial pH = 4.00-7.00. The initial NO_x removal efficiency increases as the initial pH decreases. When the initial pH was 3.50, the initial NO_x removal efficiency reached 100% under the synergistic effect of HC. Therefore, this method enhances the oxidation capacity of NaClO₂ through HC, realizes high-efficiency denitrification with low NaClO₂ concentration (1.00 mmol/L), and has better practicability for the treatment of NO_x from ships.