The influence and mechanism of weak base anion exchange resin types on NO₂ removal

NO2 is a typical atmospheric pollutant, which seriously endangers air quality and human health. Current mature denitrification technologies are mostly applied in industrial flue gas, making it difficult to remove low concentrations of NO2 under environmental conditions. This study selected macro-pore weakly basic anion exchange resin (D301) as an adsorbent to compare and investigate the NO2 adsorption performance and mechanisms of two types of D301 (salt-type and free amine-type) under dry and wet conditions. Experimental results indicate that at 35°C, the free amine-type D301 under dry conditions achieved a NOx net removal capacity of 3.11 mmol·g−1, which increased to 3.88 mmol·g−1 at 50% relative humidity, significantly higher than that of the salt-type D301. In situ adsorption infrared spectroscopy of NO2 revealed that both forms of D301 resin adsorb NO2 through physical and chemical mechanisms, albeit with significant differences in chemical adsorption mechanisms. D301-OH primarily reacts with NO2 via amine groups to produce nitrate species, nitramines, and amides, while D301-Cl reacts mainly with Cl- to produce NO3−.