DFT studies on exposure of sulfur impregnated and sulfur functionalized activated carbon to Hg0 vapors

For removal of poisonous vapor emissions such as mercury, it is necessary to select suitable materials based on an understanding of their properties and interactions with the vapor. As mercury has a high affinity towards sulfur, it’s adsorption using sulfur-impregnated activated carbon was explored in this study. The impregnation of sulfur on activated carbon followed by the adsorption of Hg⁰ vapors was computationally investigated using DFT simulations. Sulfur adsorption was investigated on activated carbon with armchair edge, zigzag edge, and graphene surface. Sulfur adsorption was investigated on activated carbon with edge functional groups such as hydroxyl and carboxylic acid. Activated carbon with edge functional groups such as sulfonic acid, sulfenic acid, and sulfinic acid was further investigated for the adsorption of Hg⁰ vapors. Among the edge functional groups on the activated carbon, the hydroxyl group was most favored for sulfur adsorption and, subsequently, Hg⁰ vapors. This was quantified in terms of shortest bond lengths, strongest binding energies, and maximum charge transfer. Among the sulfur-containing functional groups on activated carbon, sulfenic acid was the most favored for the adsorption of Hg⁰ vapors. Transition state calculations were carried out, and a reaction pathway was proposed for the adsorption of Hg⁰ on sulfur-impregnated activated carbon.