Z-scheme CeO2-TiO2@CNT Heterojunction for Efficient Photoredox Removal of Mix Pollutants (CPF, MB, MO, and RhB)

Abstract

Z-scheme CeO₂-TiO₂@CNT (CTC) heterojunction is fabricated using hydrothermal method and evaluated for removing mixed pollutants (MIX-P) from ciprofloxacin (CPF) and textile contaminations. CTC demonstrated ≈99% removal efficiency against MIX-P under solar irradiation of ≈10⁵ lumens. High removal efficiency of CTC is attributed to reduced bandgap (E_g), 2.65 eV, and high specific surface area (68.193 m² g⁻¹). Lower E_g extends light absorption that generates more charge carriers and reactive species, RS (^•O₂⁻, h⁺, ^•OH), to facilitate the photocatalytic removal process. These RS are confirmed through trapping experiments using IPA, N₂, and KI. Binding energies of 282.5, 283.7, and 285 eV, corresponding to Ti─C, Ti─O─C, and Ce─C bondings, indicated coupling of TiO₂, CeO₂, and CNT within the CTC structure. Ionic and pH tests confirmed lower photocatalytic efficiency of CTC in an alkaline environment. Photocurrent density and EIS measurements provide insights into the charge carrier dynamics, while HPLC-MS analysis offered information on degradation pathway and identification of intermediates in the removal process. DFT studies confirmed the adjustments in electronic states, structural modifications, and band alignments in agreement with experimental results. This study highlights the potential of CTC as highly effective catalyst for sustainable removal of mixed pollutants from wastewater.