Heterogeneous Fe/Zn‑exchanged clinoptilolite catalyst synthesized by solid‑state ion exchange: Fenton‑photocatalyst synergy and investigation of operational parameters for photo‑Fenton degradation of methyl orange

In the present work, heterogeneous photo‑Fenton catalysts based on natural clinoptilolite (hereafter CLI) were synthesized via simultaneous solid‑state ion exchange of iron and zinc. The resulting materials were characterized using XRD, SEM‑EDX, BET, DRS, and PL to evaluate their structural, textural, and optical properties. The findings indicated that the CLI framework remained intact after metal exchange, and both Fe and Zn were successfully incorporated into the zeolite channels. Compared with the single‑metal counterparts, the Fe/Zn‑modified samples exhibited improved textural properties and enhanced optical activity. Their catalytic performance was assessed for the degradation of methyl orange under UV irradiation in the presence of hydrogen peroxide. Among the prepared catalysts, the one with a nominal Fe to Zn molar ratio of 50:50 (denoted as Fe₅₀%/Zn₅₀‑CLI) showed the highest activity, achieving up to 92.37% decolorization under optimal conditions. This improved performance was attributed to a synergistic effect between Fe and Zn, wherein ZnO‑like species facilitate charge separation and promote the Fe³ ⁺/Fe²⁺ cycle, leading to increased hydroxyl radical generation. Kinetic analysis revealed that the degradation process followed pseudo‑first‑order kinetics and the concentration dependence of the rate constant was consistent with a Langmuir‑Hinshelwood mechanism, as confirmed by initial‑rate analysis. Overall, the Fe/Zn‑exchanged clinoptilolite catalyst demonstrates strong potential as a reusable heterogeneous photo‑Fenton system for the removal of dyes from aqueous solutions.