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

Sodium ions of TNWs were exchanged with hydrogen ions, and this protocol was very suitable for capturing high density of cobalt ions. Meanwhile, the fabricated Co₃O₄/TNWs nano-material presented a highly catalytic and stable activity for dye degradation. - Highlights: • Co₃O₄ nanoparticles were deposited on the pretreated TNWs surface. • The TNWs treated by hydrogen ions captures higher density of cobalt ions. • The Co₃O₄/TNWs catalyst possesses highly efficiency for dyes degradation with oxone. - Abstract: In this paper, we reported a recyclable and highly active porous catalyst of titanate nanowires (TNWs) coated with well-distributed Co₃O₄ nanoparticles (NPs) (Co₃O₄/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 Co₃O₄ 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 Co₃O₄ NPs with an average diameter of 22 ± 3 nm were coated uniformly on TNWs surface (average diameter: 37 ± 5.5 nm), and the Co₃O₄ NPs mainly exposed their (2 2 0) and (2 2 2) active planes. XPS analysis confirms the formation of Co₃O₄ 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 Co₃O₄/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