Catalytic oxidation of aqueous organic contaminants by persulfate activated with sulfur-doped hierarchically porous carbon derived from thiophene

- S-doped activated carbons were prepared by using thiophene as sulfur/carbon source.
- Persulfate was activated by S-doped activated carbons for organics degradation.
- Sulfur doping enhances the catalytic activity for persulfate activation.
- Non-radical pathway plays the dominate role in persulfate activation process.
- S-doped activated carbon has a good general applicability for organics degradation.

Sulfate radicals (SO4−) generated from persulfate (PS) activated by carbocatalysis is expected to provide an environmentally friendly and highly efficient catalytic oxidation process for aqueous organics degradation. Herein, a novel sulfur-doped hierarchically porous carbon with both structural and compositional modification was proposed for PS activation by using thiophene as sulfur/carbon precursor and KOH as activator. The effect of annealing temperature on its textural properties and surface chemistry was characterized by Elemental analysis, N2 sorption isotherms, X-ray photoelectron spectroscopy, Fourier transform infrared spectra, Raman spectra and X-ray diffraction. The as-prepared sample treated at 800 °C (SDAC-800) demonstrated outstanding catalytic activity for activation of PS to degrade 4-chlorophenol (4CP). Studies on the role of sulfur in the catalytic activity enhancement were carried out by comparing with a sulfur-free activated carbon and a carbon model (reduced graphene oxide (rGO)). The effects of catalyst dosage, initial 4CP concentration, and reaction temperature on 4CP degradation were comprehensively investigated. In addition, contrast tests with other conventional PS activation methods, SDAC-800 reusability and its general applicability tests were also carried out. The mechanism of PS activation and 4CP oxidation was elucidated by using quenching tests with chloridion, l-histidine and ethanol as radical scavengers. It revealed that the conventional radical pathway was not a critical role in 4CP degradation. In contrast, the process was controlled by both particle-surface interaction and non-radical pathway, and the latter played a dominant role.

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