Activation of peroxymonosulfate by surfactants as the metal-free catalysts for organic contaminant removal.

The present work described that tertiary ammonium surfactants containing bromide ion as novel metal-free catalysts were innovatively coupled with peroxymonosulfate (PMS) to build a simple catalytic oxidation system, possessing outstanding catalytic ability with organic dye Reactive Red M-3BE (RR M-3BE) as the target pollutant. Furthermore, cetyltrimethylammonium bromide (CTAB), a representative of cationic surfactant, was selected to further investigate the catalytic oxidation performance. It is found that at the critical micelle concentration (CMC) of CTAB, the oxidation efficiency of the CTAB/PMS system was optimal due to the strong electrostatic attraction between the CTA+ micelle and reactive anions (Br- and HSO5-), concentrating HSO5- and Br- at the micellar surface, which accelerated the catalytic oxidation reaction between Br- and HSO5-, generating a mass of highly active reactive species. A hybrid method that combined radical scavenger (methanol) with electron paramagnetic resonance (EPR) technology was adopted for the investigation of reactive species, and the results indicated that hydroxyl radical (•OH) was generated and had a major role in the process. The findings from this work provide a practicable pathway for highly efficient PMS activation in wastewater treatment, and also initiate a promising research area of surfactants in the field of environmental catalysis.