Efficient liquid-phase regeneration of alkaline-activated coke using iron solution: a study on the synergistic enhancement of desulfurization performance and functional strengthening

• A high-efficiency liquid-phase activated coke regeneration method based on a ferro-solution redox system was presented. • 0.04–0.06 mol/L Fe 2 (SO 4 ) 3 solution effectively restores over 85 % of activated coke's sulfur capacity at ambient conditions. • This method repairs microporous structures and enhances adsorption sites via surface hydroxylation and Fe-O bond formation. • The desulfurization efficiency remains above 90 % for 2 – 3 regeneration cycles. Conventional activated coke regeneration technologies face significant challenges, including high energy consumption, structural degradation, and secondary pollution. This study introduces a novel high-efficiency liquid-phase regeneration approach utilizing a ferro-sulfate redox system to overcome these issues. Hierarchical porous structures were constructed through alkaline activation pretreatment, and when combined with the redox synergy of a low-concentration ferric sulfate solution (0.04–0.06 mol/L), this enabled directional desorption of sulfur species and enhanced functional properties of activated coke surfaces. The experimental results indicate that the proposed regeneration process effectively restores the sulfur adsorption capacity of activated coke to over 85 % under ambient temperature and pressure, without requiring additional energy input. In comparison, conventional thermal regeneration typically consumes 200–500 kWh/t in energy. Furthermore, Brunauer-Emmett-Teller (BET) and Scanning Electron Microscopy (SEM) analyses demonstrated that a 0.04 mol/L regeneration solution optimally reconstructed microporous structures, achieving a specific surface area of 273.75 m 2 /g. In contrast, a higher concentration (e.g., 0.08 mol/L) induced pore collapse, reducing the structural integrity of the material. X-ray Photoelectron Spectroscopy (XPS) and Fourier Transform Infrared Spectroscopy (FTIR) analyses revealed that Fe 3+ /Fe 2+ redox cycling facilitates both the dissolution and oxidation of SO 2 into sulfate species, while simultaneously enhancing surface adsorption sites through surface hydroxylation and Fe-O bond formation. Kinetic studies confirm that the adsorption behavior follows the pseudo-first-order model (R 2 ≥ 0.99), indicating that physical diffusion is the dominant mechanism. Cyclic stability testing confirms the method’s robustness, maintaining >90 % desulfurization efficiency through 2–3 regeneration cycles. These findings establish a theoretical framework for both industrial flue gas desulfurization wastewater valorization and activated coke regeneration process optimization.