ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Sunlight-driven charge separation for a heterojunction of nano-pyramidal CuWO₄-MOF modified TiO₂ nanoflakes for photocatalytic degradation of ciprofloxacin

Kgaugelo S. Mabape, Shivani B. Mishra, Ajay K. Mishra, and Makwena J. Moloto

Institute for Nanotechnology and Water Sustainability, College of Science, Engineering and Technology, University of South Africa, Johannesburg, South Africa

E-mail: makwena.moloto@outlook.com

Received: 12 March 2024  Accepted: 8 September 2024

Abstract:

The study presents a breakthrough of a balanced charge separation for heterojunction CuWO₄-TiO₂ cocatalyst to efficiently enhance visible light photocatalytic degradation of ciprofloxacin (CIP). A solvothermal-synthesized nanopyramid-like CuWO₄ semiconductor was assembled before sol–gel treatment with TiO₂ precursors to generate CuWO₄-TiO₂ nanocomposites. The optical, structural, and morphological properties of CuWO₄-TiO₂ were elucidated using UV–Vis DRS, XRD, FTIR, Raman spectroscopy, and TEM/SEM techniques. The UV–Vis DRS spectroscopy of as-synthesized CuWO₄-TiO₂ cocatalyst demonstrated enhanced visible light absorbance. The XRD patterns of CuWO₄-TiO₂ revealed a triclinic phase nanocrystal. The O-Ti–O functionality was confirmed by FTIR spectroscopy. The photoactive bands corresponding to anatase redshift were observed from Raman spectroscopy of CuWO₄-TiO₂ nanocomposite. The PL studies attributed this redshift to the elevated extra energy bands that aid electron/hole pair charge separation in a co-catalyst heterojunction CuWO₄-TiO₂ nanocomposite afforded by embedding CuWO₄-MOF within TiO₂ crystalline. The TEM showed that un-sintered CuWO₄.MOF mimicked a pyramidal shape and converted to nanoflakes upon sintering, while TiO₂ and CuWO₄-TiO₂ retained a tetragonal shape. The photocatalytic activity of CuWO₄-TiO₂ cocatalyst was studied using CIP, as a model pollutant. The innovative design of 5CuWO₄-TiO₂ charge separation nanocomposite completely degraded 10 mg L⁻¹ CIP solution at pH = 6.31 (natural pH) and 9 under 120 min of sunlight irradiation.

Keywords: CuWO4-TiO2 nanocomposite; Ciprofloxacin photodegradation; CuWO4 semiconductor; TiO2 nanoparticles; Electron/hole charge pair separation

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-024-03686-x

Chemical Papers 78 (15) 8417–8432 (2024)