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A novel process for NO and SO simultaneous removal using a vacuum ultraviolet (VUV, with 185 nm wavelength)-activated O/HO/HO system in a wet VUV-spraying reactor was developed. The influence of different process variables on NO and SO removal was evaluated. Active species (O and ·OH) and liquid products (SO, NO, SO, and NO) were analyzed. The chemistry and routes of NO and SO removal were investigated. The oxidation removal system exhibits excellent simultaneous removal capacity for NO and SO, and a maximum removal of 96.8% for NO and complete SO removal were obtained under optimized conditions. SO reaches 100% removal efficiency under most of test conditions. NO removal is obviously affected by several process variables. Increasing VUV power, HO concentration, solution pH, liquid-to-gas ratio, and O concentration greatly enhances NO removal. Increasing NO and SO 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 SO. NO removals by oxidation of O, O·, and ·OH are the primary routes. NO removals by HO oxidation and VUV photolysis are the complementary routes. A potential scaled-up removal process was also proposed initially.

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The removal process of NO from SO2-containing simulated flue gas using an ultraviolet (UV)/Fenton-like reaction in a photochemical reactor was investigated. The effects of several operating parameters, such as the H2O2 concentration, Cu2+ concentration, solution pH, NO concentration, solution temperature, gas flow, SO2 concentration, and O2 concentration on NO removal were studied using a single-factor method. The liquid anions were measured by ion chromatography, and the material balances for NO and SO2 were also calculated. The results show that, with the increase in the Cu2+ concentration, NO removal efficiency significantly increases. With the increase in the H2O2 concentration, NO removal efficiency increases, but the changes gradually become smaller. NO removal efficiency greatly reduces with an increasing gas flow and NO concentration. An increasing solution temperature or SO2 concentration slightly decreases NO removal efficiency. An increase in the O2 concentration can promote the removal of NO. The anions in the liquid phase are mainly SO4 2– and NO3 –. The calculated values of SO4 2– and NO3 – are overall in agreement with the measured values.

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