A novel strategy was proposed to scrub NO x pollutant originated from sintering flue gases by oxidation combined with wet flue gas denitrification technology. CuCl 2 that could be adopted repeatedly was introduced as an additive into the sulfite solution to enhance NO 2 removal. Comparing with the sulfite solution (0.05 mol/L), the absorption efficiency improved from 75% to 100%, and the stabilization period extended from 10 to 40 min notably with the addition of CuCl 2 . The intensification by CuCl 2 addition was related to the formation of CuCl during the reaction of CuCl 2 and SO 3 2− , which was found to be more effective in removing NO 2 . Afterwards, CuCl transformed to Cu 2+ substance again and this mutual transformation between CuCl and Cu 2+ substance indicated a cyclic use of CuCl 2 additive. Moreover, the feasible reaction pathway was further proved by DFT calculations. Additionally, the investigation on NO 2 absorption at various operating parameters provided theoretical support for the practical application of CuCl 2 in denitrification.
Here, we report on using dark-field microscopy (DFM) as a simple and low-cost imaging platform to visually resolve the kinetics of single cuprous oxide (Cu2O) microparticles for NO2 removal in a real-time manner. Unexpectedly, we find that the redox reaction between Cu2O microparticles and NO2 is oscillating with the reaction time. Specifically, the oscillatory behavior of single Cu2O microparticles for NO2 reduction shows a large particle-to-particle variability, which is also dependent upon the NO2 pressure and Cu2O facets. A combined DFM imaging, spectroscopic, scanning electron microscopy, and density functional theory study uncovers that Cu2O is gradually transformed to copper nitrate hydroxide [Cu2(NO3)(OH)3], and this oscillatory reaction is attributed to the cyclic formation and structural collapse of Cu2(NO3)(OH)3. The present findings open an alternative avenue for probing structure–performance relationships, which are anticipated to benefit the creation of functional materials for air purification.
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