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

Optical and dielectric insights into visible-light-driven Rhodamine B degradation over CuAl₂O₄ spinel

Khaled Derkaoui, Ismail Bencherifa, Amal Elfiad, Khadidja Boukhouidem, Mohamed Kechouane, Yamina Mebdoua, and Toufik Hadjersi

Centre de Développement des Technologies Avancées, Alger, Baba Hassen, Algeria

E-mail: kderkaoui@cdta.dz

Received: 11 January 2026  Accepted: 20 March 2026

Abstract:

CuAl₂O₄ spinel photocatalyst was synthesized via a simple chemical route and investigated for visible-light-driven photodegradation of Rhodamine B (RhB). Unlike previous studies that mainly focus on photocatalytic activity alone, this work establishes a direct correlation between the intrinsic optical–dielectric properties of CuAl₂O₄ and its photocatalytic performance. Structural and morphological analyses confirmed the formation of a single-phase cubic spinel with a porous agglomerated morphology. Optical characterization revealed a narrow band gap of approximately 1.39 eV, while X-ray photoelectron spectroscopy valence band analysis enabled experimental construction of the electronic band structure. A comprehensive investigation of optical constants, dielectric constant, dielectric loss, relaxation time, and optical and electrical conductivity was carried out to elucidate charge carrier dynamics and polarization effects. Under visible-light irradiation, CuAl₂O₄ achieved 51.8% degradation of Rhodamine B within 90 min, following pseudo-first-order kinetics with an apparent rate constant of 9.59 × 10⁻³ min⁻¹, which is more than one order of magnitude higher than that of photolysis. Photoluminescence and electrochemical impedance spectroscopy analyses revealed suppressed charge carrier recombination and reduced charge-transfer resistance, consistent with the observed dielectric behavior. The photocatalyst exhibited good stability, retaining approximately 40% degradation efficiency after six cycles. This study demonstrates, for the first time, how optical and dielectric responses govern charge separation and photocatalytic efficiency in CuAl₂O₄, providing a structure–property–activity framework for designing spinel-based photocatalysts for visible-light-driven wastewater treatment.

Keywords: CuAl2O4 spinel; Visible-light photocatalysis; Rhodamine B degradation; Optical and dielectric properties; Charge carrier dynamics

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-026-04831-4

Chemical Papers 80 (7) 7479–7500 (2026)