Novel Process of Simultaneous Removal of Nitric Oxide and Sulfur Dioxide Using a Vacuum Ultraviolet (VUV)-Activated O₂/H₂O/H₂O₂ System in A Wet VUV–Spraying Reactor

Abstract

A novel process for NO and SO₂ simultaneous removal using a vacuum ultraviolet (VUV, with 185 nm wavelength)-activated O₂/H₂O/H₂O₂ system in a wet VUV-spraying reactor was developed. The influence of different process variables on NO and SO₂ removal was evaluated. Active species (O₃ and ·OH) and liquid products (SO₃^2-, NO₂^-, SO₄^2-, and NO₃^-) were analyzed. The chemistry and routes of NO and SO₂ removal were investigated. The oxidation removal system exhibits excellent simultaneous removal capacity for NO and SO₂, and a maximum removal of 96.8% for NO and complete SO₂ removal were obtained under optimized conditions. SO₂ reaches 100% removal efficiency under most of test conditions. NO removal is obviously affected by several process variables. Increasing VUV power, H₂O₂ concentration, solution pH, liquid-to-gas ratio, and O₂ concentration greatly enhances NO removal. Increasing NO and SO₂ concentration obviously reduces NO removal. Temperature has a dual impact on NO removal, which has an optimal temperature of 318 K. Sulfuric acid and nitric acid are the main removal products of NO and SO₂. NO removals by oxidation of O₃, O·, and ·OH are the primary routes. NO removals by H₂O₂ oxidation and VUV photolysis are the complementary routes. A potential scaled-up removal process was also proposed initially.