Effects of oxygenated groups on the adsorption removal of dibenzofuran by activated coke: Experimental and DFT studies

Abstract

Activated cokes integrated removal technologies have been widely used to abate polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in sintering flue gas. A series of comparative adsorption experiments were performed by using nitric acid (HNO3) treated activated coke with dibenzofuran as model pollutants. The physicochemical properties of activated cokes were analyzed by using various characterization methods. Combined with the results of experiments, the interactions of typical oxygenated groups with dibenzofuran were also calculated by density functional theory to reveal the nature relationships among the textural properties, oxygenated functional groups and dibenzofuran adsorption behaviors. It was demonstrated through adsorption experiments that adsorption capacity decreased with the enhanced oxidation degrees of activated cokes. Especially the adsorption capacities of activated cokes were probably deteriorated by the hydrophilic carboxyl and anhydride groups. In contrast, a higher adsorption rate was obtained with the increasing oxidation degrees. It was revealed through the density functional theory analysis that physical adsorption dominated the adsorption of dibenzofuran on activated cokes, and dibenzofuran was adsorbed preferentially on the activated cokes with oxygenated groups. Moreover, the formation of oxygenated groups increased the adsorption energy of dibenzofuran on activated cokes and accelerated the adsorption process. However, the enhanced competitive adsorption of oxygen (O2) also led to the reduction of adsorption capacity for dibenzofuran. This study not only gives a sophisticated understanding for the relationship between surface oxygenated groups and dioxins adsorption abatement but also offers referential guidance for the design of carbonaceous adsorbent suitable for the adsorption of PCDD/Fs.