CO2-activated porous semi-coke for peroxydisulfate activation: Enhanced tetracycline degradation via non-radical pathways

Porous semi-coke activated carbon (SAC) was synthesized from semi-coke (SC) through CO 2 physical activation at elevated temperatures. SAC has a high specific surface area , hierarchical porous structure, and abundant oxygen-containing functional groups, which can effectively activate peroxydisulfate (PS) to degrade tetracycline (TC) in water. The results of the characterization demonstrated that the elevated pyrolysis temperature led to an augmentation in the specific surface area, defect degree and oxygen-containing functional groups of SAC. The SAC1000, with specific surface area of 496.70 m 2 ∙g −1 , exhibited the optimal degradation efficiency of 94.72 % and the mineralization rate of 69.11 % for TC. In addition, SAC1000 exhibited the favorable reusability, exhibiting a degradation efficiency of 81.74 % after five cycles. The addition of inorganic salt ions (HCO 3 − , H 2 PO 4 − , and Cl − ) and humic acid exerted a barely perceptible influence on the degradation of TC. Investigation of the catalytic mechanism showed that the non-radical pathway ( 1 O 2 and electron transfer pathway) was the major PS activation mechanism. The abundant defect structure and C=O/O=C-O groups of SAC1000 were the primary redox active sites of ROS . This study innovatively synthesized CO 2 -activated porous semi-coke activated carbon from industrial waste for peroxydisulfate activation, which provides an environmentally sustainable treatment for semi-coke wastes and promotes the development of green carbon-based catalysts. • CO 2 -activated porous Semi-coke was prepared. • Efficient TC degradation was achieved in the SAC1000/PS system. • 1 O 2 and electron transfer played a key role in TC degradation. • Surface defects and C=O/O=C-O groups are the primary active sites. • TC degradation is less affected by solution pH and coexisting ions.