Enhanced activation process of persulfate by mesoporous carbon for degradation of aqueous organic pollutants: Electron transfer mechanism

[Display omitted] •Hexagonally-ordered mesoporous carbon (CMK-3) can efficiently activate persulfate.•The relationship between adsorption and oxidation process in CMK-3/PS system was discussed.•The active sites and reasons for passivation of CMK-3 were revealed.•A two-pathway mechanism was proposed for metal-free activation process of PS.•CMK-3/PS system exhibited high efficiency in pharmaceutical wastewater treatment. Metal-free catalysis for green degradation of aqueous organic pollutants has caused extensive concern in recent years. In this study, hexagonally-ordered mesoporous carbon (CMK-3) was applied to activate persulfate (PS) for the degradation of 2,4-dichlorophenol (2,4-DCP) with superior removal rate of 90% in 20 min. The high catalytic efficiency was probably ascribed to the accelerated electron transfer resulting from the large adsorption capacity of CMK-3. It was found that specific surface areas (SSA), defective sites and functional groups on the activator were highly related to its catalytic efficiency and passivation. Compared to other nanocarbons, CMK-3 had better reusability due to its ordered mesoporous structure with large SSA and high defective degrees. For the first time, a two-pathway mechanism was proposed for metal-free activation process of PS, indicating that radical and non-radical oxidation worked together in PS activation for complete 2,4-DCP decomposition, and non-radical pathway played a dominant role while radical pathway was critical in accelerating the reaction. OH, SO4− and O2− all took part in the radical oxidation process, in which the contribution of OH was dominant. Besides, high decomposition efficiency was also achieved in pharmaceutical wastewater treatment by the CMK-3/PS system. This research proposed a new electron transfer mechanism for metal-free activation process of PS, which can provide a theoretical support for further studies.