Study of Molding–Regeneration Process of Powdered Spent Activated Carbon: Response Surface Methodology Optimization and Regeneration Mechanism

A regeneration process for powdered spent activated carbon was developed through binder-assisted forming and thermal regeneration, and the process parameters were optimized by using response surface methodology (RSM). The effects of calcination time, calcination temperature, and binder ratio on the iodine adsorption value of spent activated carbon were investigated by using a Central Composite Design. The quadratic regression model exhibited high accuracy and statistical significance (R2 = 0.9934, p < 0.0001), indicating good agreement between the predicted and experimental results. The optimal regeneration conditions were determined as a calcination time of 39.2 min, a calcination temperature of 848 °C, and a binder ratio of 10.15%. Under the optimized conditions, the VOCs (dichloromethane) adsorption capacity increased sharply from 9.1 mg/g to 108.2 mg/g. Characterization results showed that the regeneration process effectively restored the pore structure and improved the surface properties of the activated carbon. Thermogravimetric analysis demonstrated the effective removal of adsorbed pollutants. XPS analysis revealed a decrease in oxygen-containing functional groups, particularly –COOH groups, accompanied by an increase in C=O content, while the C–O groups changed only slightly. These structural and surface modifications contributed to the recovery of adsorption performance and provide guidance for the regeneration of powdered spent activated carbon.