Experimental Study on the Influence of Surface Characteristics of Activated Carbon on Mercury Removal in Flue Gas

Abstract

The influences of the physical features and chemical properties of activated carbon on Hg0 adsorption were investigated. The textural characteristics of the samples were studied by Brunauer–Emmett–Teller analysis and scanning electron microscopy. The chemical properties of the samples were characterized by energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The results show that the oxygen-containing functional groups on activated carbon have a great influence on Hg0 adsorption and the functional groups increase the acidity, polarity, and hydrophobicity of the carbon surface and promote the Hg0 adsorption. The Hg0 adsorption of activated carbon mainly manifests as chemical adsorption. The desorbed activated carbon almost has no Hg0 removal ability although it still has a huge surface area and a microspore structure. The oxygen-containing functional groups on the surface play a key role in Hg0 adsorption. Among them, carbonyl, carboxyl, and ester groups promoted mercury adsorption, while the phenolic hydroxyl group induced inhibition. The process of Hg0 adsorption on modified activated carbon could be described with the pseudo-second-order model, which indicated that the chemisorption is the dominant step in the Hg0 removal process by modified activated carbon. Kinetic calculation results also show that under a given gas condition, modified activated carbon possessed a bigger equilibrium adsorption capacity but displayed poor adsorption kinetics.