Photocatalytic degradation of oxytetracycline with Pr3+-Bi3+ co-doped SrZrO3 materials

Abstract

The occurrence of antibiotics in the aquatic environment has raised concern due to their ecotoxicological effects. Among the available strategies for their removal, heterogeneous photocatalysis has emerged as a promising approach. SrZrO₃ has been investigated as a photocatalyst, however, its practical application is limited by its wide band gap (E_g, ∼5.6 eV). In this study, the effect of Bi³⁺–Pr³⁺ co-doping on the photocatalytic activity of SrZrO₃ was systematically evaluated. The Bi³⁺ content was fixed at 1 mol%, while the Pr³⁺ concentration was varied according to the general formula SrZr_0.99-xBi_0.01Pr_xO₃ (0 ≤ x ≤ 3 mol%). The materials were synthesized via the polymerizable-complex (Pechini) method and calcined at 900 °C and 1100 °C for 1 h. The XRD analysis confirmed that all samples crystallized into an orthorhombic structure. Co-doping effectively reduced the E_g from 3.84 eV to <3.16 eV. Among the prepared materials, SrZr_0.975Bi_0.01Pr_0.015O₃ material calcined at 900 °C for 1 h displayed the highest photocatalytic performance, achieving 92.7 % oxytetracycline (OTC) degradation with a rate constant of 0.0110 min⁻¹. The scavenger experiments using N₂, formic acid, and isopropanol revealed that photo-generated holes are the dominant reactive species driving the degradation process. Photocatalysis tests carried out in tap water and secondary effluent demonstrated a decrease in photocatalytic efficiency, due to the presence of competing dissolved organic matter. Recycling tests demonstrated that the best photocatalyst remained stable with acceptable reusability. Therefore, Bi³⁺–Pr³⁺ co-doping is confirmed as an effective strategy to narrow the SrZrO₃ band gap and enhance its photocatalytic activity toward OTC degradation, underscoring its potential application in wastewater treatment.