Mechanistic and Kinetic Study of Tetrabutylammonium Bromide for Facilitating NO₂ Absorption in Sulfite Solutions with Inhibition of O₂–Induced Oxidation

An innovative strategy in wet flue gas denitration technology was proposed to control nitrogen oxide emissions from cement kiln. Here the use of tetrabutylammonium bromide (TBAB) as an additive improved the absorption and utilization efficiency of sulfite absorbents for NO₂. Compared with the sulfite solution, the stability time and absorption efficiency of adding TBAB were increased from 25 to 76 min and from 91.2 to 98.4%, respectively. Continuous absorption for 480 min indicated the feasibility of TBAB for repeated use. Moreover, we propose an antioxidant mechanism, including the capture of SO₃^•- by TBA⁺, and the reduction of SO₃^•- by Br^-. The successive steps kept the sulfite from the cyclic depletion of the radical chain reaction of "Generate SO₃^•--Introducing O₂-Consuming SO₃^2-" due to O₂. A new application of TBAB in free radical trapping and antioxidant is given. Furthermore, a kinetic model describing the macroscopic absorption rate was developed based on different operating conditions.