Mesoporous carbon derived from anaerobic granular sludge through molten salt method and its application for dye adsorption: an experimental and molecular dynamics simulation study

Sludge, a kind of carbon-rich material, can be produced as activated carbon. Mesoporous carbon derived from sludge has advantages in dye adsorption. However, most studies focus on the characteristic of surface area, pore volume, and pore size distribution but not the adsorption kinetics of mesoporous carbon. In this study, mesoporous carbon was prepared from anaerobic granular sludge through the molten salt method. The highest specific surface area can be 728.67 m2 g−1 at calcination temperature of 500 °C and time of 2 h. The removal of methylene blue (MB) and methyl orange (MO) can be above 99% with the dye concentration of 40 mg L−1. MB and MO adsorption experiment fitted well with pseudo-second-order kinetics. According to molecular dynamics simulation, the adsorption of MO on the surface of mesoporous carbon was easier than that of MB, while MB and mesoporous carbon system was stable. The frontier molecular orbital analysis was consistent with the experiment results. The sludge-derived activated carbon prepared by molten salt method had typical mesoporous structure and enhanced the dye adsorption.