The low-temperature (–20~ –40 ℃) oxidation adsorption of multiple pollutants from coal-fired flue gas onto activated carbons enables their integrated removal, which has promising application prospect and environmental benefits.

This article studied the adsorption processes of NO and SO₂ by four activated carbons (graded-pore activated carbon, coal-based activated carbon, and two coconut shell-based activated carbons) in inert atmosphere and simulated flue gas under low temperature conditions of –20 ℃.

The experimental results showed that in an inert atmosphere, the adsorption performance of the four activated carbons for NO was weak, with a saturated nitrogen capacity of less than 0.07 mg/g, and the saturated sulfur capacity for adsorbing SO₂ was 31.70~57.07 mg/g. In simulated flue gas conditions, the presence of O₂ increased the saturated nitrogen capacity of activated carbons by three orders of magnitude and the saturated sulfur capacity by 2~5 times. The optimal coconut shell activated carbon-2 had a saturated nitrogen capacity of 175.70 mg/g and a saturated sulfur capacity of 320.65 mg/g. Density functional theory (DFT) calculations show that the adsorption binding energies of NO, SO₂, and their oxides on the zigzag edge carbon model follow the order of NO₂> SO₃> SO₂> NO. After NO and SO₂ are oxidized by O₂ into NO₂ and SO₃, their adsorption on activated carbon surfaces is significantly enhanced.

The research results can provide an important theoretical basis for the integrated adsorption and removal of NO and SO₂ in coal-fired flue gas under low temperature conditions.