Microwave Irradiation Induced High-Efficiency Regeneration for Desulfurized Activated Coke: A Comparative Study with Conventional Thermal Regeneration

Low desorption efficiency and inferior adsorbate recovery rate during conductive-heating regeneration have always been the key issues facing activated carbon-based SO₂ removal technology, which commonly leads to a short cycling life of an adsorbent. Herein, microwave heating was employed to regenerate desulfurized activated coke, which demonstrates great improvements in regeneration efficiency and cycling desulfurization performances. Compared with the long-time conductive-heating process (30 min), microwave heating shows a more rapid heating rate with just 4 min to achieve complete regeneration. After 10 desulfurization-regeneration cycles, microwave regenerated activated coke (MG-AC) can still maintain a high SO₂ removal capacity of 94 mg g^-1, more than double than that of thermal regenerated AC (TG-AC). Physicochemical structures analyses confirm that microwave heating selectively activates the adsorbate H₂SO₄ molecules and thus promotes the porosity development and selective removal of oxygen-containing functional groups. Additionally, surface sulfur species analysis provides a new insight into the adsorbate desorption mechanism that microwave irradiation could create instantaneous high temperature within activated coke and induce deep reduction of H₂SO₄ to elemental sulfur. This finding is of great significance for the development of high-value sulfur recovery technology. This work also suggests that microwave heating is an attractive method for the high-efficiency regeneration of desulfurized activated coke.