¹ Department of Physics, University of Agriculture, Faisalabad 38040, Pakistan;

² Department of Chemistry, University of Agriculture, Faisalabad 38040, Pakistan

* Correspondence: hafeez.anwar@gmail.com

Dye pollution harms the environment, but photocatalysis provides an eco-friendly remedy. Dy³⁺-doped ZnFe₂O₄ with different weight ratios of g-C₃N₄ were synthesized via
co-precipitation for RhB dye degradation. XRD confirmed a cubic structure with crystallite sizes of 20–30 nm, while SEM showed grain sizes of 8–24.5 nm. FTIR (650–4000 cm⁻¹) confirmed O–H, C–N, and C=N groups; UV–Vis showed band gaps of 1.98–1.74 eV. The dielectric constant peaked at low frequencies (31.6–3162 Hz), and AC conductivity reached 1.4 × 10⁻⁶(Ωm)⁻¹. Optimal photocatalytic performance was achieved at pH 8, 40 mg/100 mL catalyst dose, and 8 mM H₂O₂ using Dy³⁺-doped ZnFe₂O₄ with composite g-C₃N₄ (0.4g), attaining ≈96.5% RhB degradation within 75 min. This composite showed good reusability over five cycles, confirming its high efficiency for water contaminant removal.