The potential of activated carbon made of agro-industrial residues in NOx immissions abatement

Abstract

The treatment of NOx from automotive gas exhaust has been widely studied, however the presence of low concentrations of NOx in confined areas is still under investigation. As an example, the concentration of NO2 can approximate 0.15 ppmv inside vehicles when people are driving on highways. This interior pollution becomes an environmental problem and a health problem. In the present work, the abatement of NO2 immission is studied at room temperature. Three activated carbons (ACs) prepared by physical (CO2 or H2O) or chemical activation (H3PO4) are tested as adsorbents. The novelty of this work consists in studying the adsorption of NO2 at low concentrations that approach real life immission concentrations and is experimentally realizable. The ACs present different structural and textural properties as well as functional surface groups, which induce different affinities with NO2. The AC prepared using water vapor activation presents the best adsorption capacity, which may originate from a more basic surface. The presence of a mesoporosity may also influence the diffusion of NO2 inside the carbon matrix. The high reduction activity of the AC prepared from H3PO4 activation is explained by the important concentration of acidic groups on its surface.