Ultrasound-induced aqueous removal of nitric oxide from flue gases: Effects of sulfur dioxide, chloride, and chemical oxidant

The effects of sulfur dioxide (SO ₂), sodium chloride (NaCl), and peroxymonosulfate or oxone (2KHSO ₅·K ₂SO ₄·K ₂SO ₄ with active ingredient, HSO ₅ ^-) on the sonochemical removal of nitric oxide (NO) have been studied in a bubble column reactor. The initial concentration of NO studied ranged from about 500 to 1040 ppm. NaCl in the concentration range of 0.01-0.5 M was used as the electrolyte to study the effect of ionic strength. At the low NaCl concentration (0.01 M), the percent fractional removal of NO with initial concentration of 1040 ppm was enhanced significantly, while as the NaCl concentration increased, the positive effects were less pronounced. The presence of ∼2520 ppm SO ₂ in combination with 0.01 M NaCl further enhanced NO removal. However, with a NO initial concentration of 490 ppm, the addition of NaCl was detrimental to NO removal at all NaCl concentration levels. The combinative effect of sonication and chemical oxidation using 0.005-0.05 M oxone was also studied. While the lower concentrations of HSO ₅ ^- enhanced NO removal efficiency, higher concentrations were detrimental depending on the initial concentration of NO. It was also demonstrated that in the presence of ultrasound, the smallest concentration of oxone was needed to obtain optimal fractional conversion of NO.