Simultaneous Removal of SO₂ and NO Using a Novel Method of Ultraviolet Irradiating Chlorite–Ammonia Complex

Abstract

A novel advanced oxidation process (AOP) using ultraviolet/sodium chlorite (UV/NaClO2) is developed for simultaneous removal of SO2 and NO. NH4OH, as an additive, was used to inhibit the generation of ClO2 and NO2. The removal efficiencies of SO2 and NO reached 98.7 and 99.1%. NO removal was enhanced by greater UV light intensity and shorter wavelengths but was insensitive to changes in pH and temperature. SO2 at 500–1000 mg/m3 improved NO removal, especially in the absence of UV. The coexistence of SO2 and O2 facilitated the removal of NO by ClO2 –. HCO3 –, Cl–, and Br– enhanced NO removal, but their roles were negligible when UV was added. The generation of ClO2 and ClO•/HO• was verified by an UV–vis spectrometer, electron spin resonance (ESR), and radical-quenching tests. The mechanisms responsible for the removal of SO2 and NO were attributed to the synergism between acid–base neutralization and radical-induced oxidation. The ClO2 – evolution and product composition were demonstrated by UV–vis and X-ray photoelectron spectroscopy (XPS). Kinetics analyses showed that the Hatta numbers were 329–798 and 747–1000 without and with UV. Thus, the gas–film resistance mainly controlled the mass-transfer process.

Ultrasonic role to activate persulfate/chlorite with foamed zero-valent-iron: Sonochemical applications and induced mechanisms

“…Meanwhile, when pH presented alkaline, the reaction rate both in Fe 0 f -O SC and US/Fe 0 f -O SC seemed to be accelerated, but it would decelerate. The greater the alkaline, the more obvious the above-mentioned phenomenon, which could be ascribed to ClO 2 − (alkali activation to form ClO• being different from acidic reaction to generate ClO 2 ) [20] , [22] . The S 2 O 8 2− was dominant, thus the alkali role to ClO 2 − could not sustain over the whole reaction process.…”

“…In addition, the ClO 2 was detected by UV–Vis spectrum (ClO 2 different from other chlorines in water, existing absorption peak around 360 nm) [20] , [21] . From Fig.…”

“…ionic Fe cycle) under the action of US, the chlorite (ClO 2 − , Cl(III)) could be introduced into the aforementioned process and combined with persulfate to form composite oxidants. Commonly, ClO 2 − with a higher quantum yield at 254 nm, 1.0–1.53 mol⋅Einstein -1 [18] , [19] , comparing with H 2 O 2 (0.5 mol⋅Einstein -1 ) and persulfate (0.7 mol⋅Einstein -1 ) [20] , could be activated by physical fields including UV-light stimuli ( [18] , Eq. (6) ), heat [21] , and US, or chemical agents including acid (Eq.…”

Scale-up experiments of SO2 removal and the promoting behavior of NO in moving beds at medium temperatures

“…Besides, high-energy electron activation oxidation technologies [33][34][35][36][37] and photo-catalysis technologies have been attempted, [38][39][40][41] but these technologies are challenging to achieve high denitrication efficiency and lower the cost.…”

Macroscopic Kinetics of Simultaneous Desulfurization and Denitrification by MgO/NaClO2 Solution

“…Pollutants such as sulfur dioxide (SO 2 ) and nitrogen oxides (NO x ) released from the combustion of a large amount of coal are the leading causes of atmospheric environmental problems such as photochemical pollution, acid rain, ozone, and regional haze [1][2][3] . As the primary pollution sources, the SO 2 and NO x discharged from coal-fired power plants have been effectively controlled in recent years, and the intensification of atmospheric pollution has been alleviated.…”