A recyclable and highly active Co3O4 nanoparticles/titanate nanowire catalyst for organic dyes degradation with peroxymonosulfate

In this paper, we reported a recyclable and highly active porous catalyst of titanate nanowires (TNWs) coated with well-distributed Co 3 O 4 nanoparticles (NPs) (Co 3 O 4 /TNWs). Sodium ions of TNWs were exchanged with hydrogen ions in the dilute nitric acid, and this protocol was very suitable for capturing cobalt ions. X-ray diffraction (XRD) demonstrated the existence of Co 3 O 4 phase with unique lattice planes, such as (2   2   0), (3   1   1) and (5   1   1). Electron microscopes (FE-SEM and TEM) indicated that the Co 3 O 4 NPs with an average diameter of 22   ±   3   nm were coated uniformly on TNWs surface (average diameter: 37   ±   5.5   nm), and the Co 3 O 4 NPs mainly exposed their (2   2   0) and (2   2   2) active planes. XPS analysis confirms the formation of Co 3 O 4 phase by the presence of Co 2p peaks at 780.1   eV (2p 3/2) and 795.5   eV (2p 1/2). Methylene blue (MB) and other organic dyes (rhodamine B (RhB) and methyl orange (MO)) were chosen as target compounds for catalytic degradation under indoor scattering light. Compared to the original Co 3 O 4 /TNWs catalyst, the catalytic efficiency of nanoscaled catalyst with oxone for MB was about 15 times higher, and the MB solution (10   mg   L −1 ) was completely degraded within 8   min. The catalytic activity of recycled catalyst used in the sixth run still remained very active, and the degradation time for MB was only 16   min. The nanosized catalyst also had a high activity for dyes of RhB (10   mg   L −1 ) and MO (10   mg   L −1 ), as the degradation efficiencies of RhB and MO after 10   min of contact time were about 90.2% and 92.6%, respectively.