Nanocrystalline ferrihydrite activated peroxymonosulfate for butyl-4-hydroxybenzoate oxidation: Performance and mechanism.

Heterogeneous catalysts activated peroxymonosulfate (PMS) for degradation of refractory organic contaminants has been recognized as a promising removal technology for the environmental remediation. In this study, nanocrystalline ferrihydrite (NFH) was prepared to activate PMS for the degradation of butyl-4-hydroxybenzoate (BHB). XPS analysis indicates that calcination process played a key role in regulating the surface oxygen species of NFH, thus control its activation ability toward PMS. NFH exhibits excellent stability (the released concentration of Fe ions < 0.13 mg/L) and desirable reusability. Increasing solution temperature and NFH dosage exerted a positive role in PMS activation for BHB removal, while such positive correlation was not found in the case of increasing initial pH. Increasing the static solution dissolved oxygen remarkably enhanced BHB oxidation kinetics. However, continuous N and air blowing caused a significant decline in BHB removal. Reaction mechanism study showed that SO, OH, O, and O were the main reactive oxygen species for degrading BHB by NFH/PMS. LC/MS analysis indicated BHB was degraded by the pathways of hydroxylation, carboxylation, decarboxylation, dehydrogenation, ring cleavage and chain cleavage reaction. This work suggests the ferrihydrite might be a promising catalyst to activate PMS to destroy refractory organic pollutants in the environmental remediation.