Synthesis, structural characterization, and solar photocatalytic performance of porous Pr-modified ZnO microparticles for organic dye degradation

Pr-modified ZnO microparticles were synthesized through a precipitation-based approach and evaluated as photocatalysts for the degradation of methylene blue (MB) under natural solar irradiation. The synthesized materials were characterized to investigate their structural, optical, morphological, thermal, and textural properties. Optical analysis yielded band-gap energies of approximately 3.14 eV for pristine ZnO and 3.17 eV for Pr-modified ZnO, indicating that Pr modification produced only a minor change in the optical band gap. N₂ adsorption-desorption analysis of Pr-modified ZnO revealed a BET specific surface area of 52.65 m² g⁻¹, while BJH analysis yielded a pore volume of 0.305 cm³ g⁻¹ and an average pore diameter of 15.98 nm, supporting its mesoporous textural characteristics. Photocatalytic activity was evaluated using MB solutions with initial concentrations of 10, 15, and 20 mg L⁻¹ under natural solar irradiation. After 120 min, Pr-modified ZnO achieved degradation efficiencies of 99.55%, 98.99%, and 97.04%, respectively. Apparent pseudo-first-order analysis yielded rate constants of 0.03945, 0.03180, and 0.02730 min⁻¹ for 10, 15, and 20 mg L⁻¹ MB, respectively. The results demonstrate efficient MB decolorization/degradation by Pr-modified ZnO under natural solar irradiation and show that the degradation rate decreases with increasing initial dye concentration. The combination of mesoporous textural characteristics and solar photocatalytic activity highlights Pr-modified ZnO as a promising material for further investigation in photocatalytic water treatment. Nevertheless, additional studies addressing mineralization, recyclability, charge-carrier dynamics, and reactive-species identification are required to establish its long-term performance and photocatalytic mechanism.