Efficient activation of peroxymonosulfate by nanotubular Co3O4 for degradation of Acid Orange 7: performance and mechanism.

Abstract

Morphology optimization of catalysts has been considered as a viable strategy to improve the catalytic efficiency for peroxymonosulfate (PMS) activation by providing high surface area and abundant active sites. In this study, nanotubular Co3O4 (NT-Co3O4) was successfully synthesized as a PMS activator for the rapid removal of acid orange 7 (AO7) in aqueous solutions. Characterization results showed that NT-Co3O4 presented as aggregated nanotubes, with an average pore diameter of 10 nm. The specific surface area of NT-Co3O4 was as high as 41.8 m2 g-1. Catalytic experiments demonstrated that the degradation rate of AO7 in the NT-Co3O4/PMS system was 15 times greater than that in commercially available Co3O4/PMS system. The effects of various experimental parameters, including catalyst dose, PMS dose, pH, and temperature, were comprehensively investigated. The reactive species in the NT-Co3O4/PMS system were identified as sulfate radical (SO4•-) through both quenching tests and electron paramagnetic resonance (EPR) technology, and ≡CoOH+ played an important role in PMS activation. N atoms in the AO7 molecule were found to be preferentially attacked by SO4•-. Moreover, the good stability and reusability of NT-Co3O4 were confirmed by a five-cycle AO7 removal experiment. This study provides a broader view of the potential applications of nanotubular materials to achieve highly efficient PMS activation in treating dyes in wastewater.