Microwave-assisted ammonia modification of activated carbon for effective removal of phenol from wastewater: DFT and experiment study

Insight into the microcosmic mechanism of the nitrogen functionalized activated carbon for phenol removal from wastewater has attracted widespread attention. In this work, density functional theory (DFT) calculations were adopted to investigate the adsorption behaviors of phenol molecules on different nitrogen-containing groups of activated carbon. Ammonia modification under microwave radiation was performed to adjust surficial chemical characteristics for maximizing phenol adsorption capacity of activated carbon. The DFT results demonstrated that phenol molecules were favorable for adsorption on the pyridine group and quaternary nitrogen group of activated carbon, and these were attractive enough to resist the interference of water adsorption. In the side adsorption configurations, the adsorption of phenol molecule on the surface of amine group, pyrrole group and all the oxygen functional groups was not stable due to competitive adsorption of water molecules. Combined with the experimental results, it could be inferred that the excellent phenol adsorption capacity of the micro-wave-assisted ammonia modified activated carbon resulted from the conversion of surface chemistry properties to low oxygen and high nitrogen components. Among the nitrogen-containing functional groups on the modified activated carbon surface, formation of pyridine groups was proved to be the key for phenol uptake.