Effect of nitrogen- and oxygen-containing functional groups on adsorption of styrene by activated carbon: A theoretical study by density functional theory

Activated carbon adsorption is one of the mainstream technologies for controlling VOCs emissions such as styrene, with surface functional groups significantly influencing its adsorption capacity. The adsorption mechanism of styrene on functionalized AC was studied using DFT calculations. Results show that nitrogen and oxygen doping altered the local electrostatic potential of AC, reduced the average LOLIPOP index of the internal ring, and enhanced styrene adsorption to varying degrees. AC with hydroxyl and pyrrolic groups significantly improved styrene adsorption (Ead = -13.76, -12.86 kcal/mol). Styrene adsorption on AC is a physisorption process, primarily dominated by π-π stacking, with dispersion interactions as the main contributor (61–70 %). In addition to π-π stacking, weak hydrogen bonds between styrene and AC functionalized with hydroxyl, amino, and pyrrolic N groups further enhance the adsorption capacity. Enhancing the synergistic effect of hydrogen bonding and π-π stacking is key to significantly improving adsorption capacity.