Modification of coal gasification slag-based activated coke by KOH activation method and its adsorption performance on methyl orange

KOH activation was used to chemically activate coal gasification slag to prepare activated coke with high adsorption performance. Experimental investigation revealed that the optimal conditions for activating coke were achieved with an alkaline carbon mass ratio of 3.5:1, activation temperature of 850 °C, and duration of 45 min, resulting in superior adsorption performance for methyl orange (MO). Structural analysis unveiled that the activated coke (KAC-CRGS) exhibited a substantial abundance of micropores on its surface, complemented by the presence of mesopores , leading to a specific surface area of 422.16 m 2 /g, a total pore volume of 0.30 cm 3 /g, and a microporous volume of 0.0807 cm 3 /g. Adsorption experiments demonstrated that the adsorption behavior of MO by the activated coke adhered to the Langmuir isotherm adsorption equation, with a maximum unit adsorption capacity of 139.49 mg/g at 35 °C. The adsorption process was found to be spontaneous and exothermic, fitting a quasi-second-order kinetic model . After four cycles of repeated adsorption experiments, the adsorption capacity of KAC-CRGS for MO decreased from 120.68 mg/g to 103.62 mg/g. The adsorption mechanism study indicates that the adsorption of MO by KAC-CRGS primarily involves chemical adsorption mechanisms such as electrostatic attraction , van der Waals forces, hydrogen bonding , and π-π stacking, with physical adsorption mechanisms such as pore diffusion and pore filling serving as a secondary means.