Removal of toluene and SO2 by hierarchical porous carbons: a study on adsorption selectivity and mechanism
2022
Huang, Xinlei | Li, Hongxian | Wang, Ling | Tang, Minghui | Lu, Shengyong
The coal combustion produces a large amount of pollutants such as organic compounds pollutants (such as VOCs, SVOCs) and conventional pollutants (such as SO₂, NOx) which need to be controlled in coal-fired plants. Currently, there have been mature emission control technologies for conventional pollutants in coal-combustion flue gas. The complicated conditions of flue gas will have great effects on the property of VOCs adsorbents. Thus, high-quality adsorbents with great adsorption properties and selectivity of VOCs are urgently needed. In this work, a biomass-derived hierarchical porous carbon (HPC-A) with high adsorption capacity (585 mg/g) and great selectivity of toluene was proposed. Analyses through the competitive adsorption tests between toluene and SO₂ indicated that the pore size distributions of adsorbents dominate the adsorption capacity and selectivity. The ultramicropores (< 0.7 nm) determine the SO₂ adsorption capacity and promote the SO₂ adsorption selectivity, while the micropores of 0.7 ~ 2 nm and mesopores are beneficial for toluene adsorption. Intriguingly, the SO₂ molecules can promote the toluene adsorption kinetics on hierarchical porous carbons through occupying ultramicropores when competitive adsorption. Besides, we indicated the mechanism of adsorption capacity, selectivity, and kinetics of toluene and SO₂, and great reusability of HPC-A was found through toluene cyclic adsorption tests. The HPC-A could be a potential adsorbent for VOCs removal from coal-combustion flue gas.
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