Transition metaldoped TiO₂ and CeO₂ photocatalysts modified with Ti₃C₂ MXene for PMS-driven advanced oxidation of pharmaceutical pollutants

Abstract

Pharmaceutical residues are increasingly persistent in aquatic environments due to their chemical stability andresistance to conventional wastewater treatment. To address this, we developed a two-step, performance-guidedsynthesis of TiO₂- and CeO₂-based photocatalysts: first doped with transition metals (Fe, Ni, Cu, Mo, Pd) andsubsequently modified with 2D Ti₃C₂ MXene to enhance peroxymonosulfate (PMS) activation under UV andvisible light. Among the dopants, Fe and Ni imparted the most favorable physicochemical features, includingnarrowed optical band gaps, increased oxygen vacancy concentrations, and reduced photogenerated chargerecombination, as evidenced by UV–vis, XPS, and photoluminescence analyses. Post-synthetic MXene integrationimproved interfacial charge separation and visible-light absorption, achieving >99 % total organic carbon (TOC)mineralization of a ternary pharmaceutical mixture (tetracycline, levofloxacin, and paracetamol) in real tapwater under UV irradiation. Comprehensive structural (XRD, Raman, TEM), optical (UV–vis DRS, PL), andsurface (XPS) characterizations identified the Ni–CeO₂–MXene composite as the most efficient, showing optimaldefect structure, redox activity, and electronic conductivity. The catalyst maintained >95 % activity over fivereuse cycles, with minimal leaching confirmed by ICP-OES. Post-reaction XPS revealed moderate surfacemodification (Ce4+/Ce3+ and Ni2+/Ni3+ ratios shift) without signs of structural degradation. Kinetic analysisconfirmed pseudo-first-order degradation with high rate constants and short half-lives, highlighting theirapplicability for rapid pharmaceutical mineralization. This study proposes a rational and selective approach forcoupling metal doping and 2D conductive interfaces, enabling the scalable design of stable and efficient photocatalystsfor PMS-driven advanced oxidation processes (AOPs) in water purification