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

Pharmaceutical residues are increasingly persistent in aquatic environments due to their chemical stability and resistance to conventional wastewater treatment. To address this, we developed a two-step, performance-guided synthesis of TiO₂- and CeO₂-based photocatalysts: first doped with transition metals (Fe, Ni, Cu, Mo, Pd) and subsequently modified with 2D Ti₃C₂ MXene to enhance peroxymonosulfate (PMS) activation under UV and visible light. Among the dopants, Fe and Ni imparted the most favorable physicochemical features, including narrowed optical band gaps, increased oxygen vacancy concentrations, and reduced photogenerated charge recombination, as evidenced by UV–vis, XPS, and photoluminescence analyses. Post-synthetic MXene integration improved 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 tap water under UV irradiation. Comprehensive structural (XRD, Raman, TEM), optical (UV–vis DRS, PL), and surface (XPS) characterizations identified the Ni–CeO₂–MXene composite as the most efficient, showing optimal defect structure, redox activity, and electronic conductivity. The catalyst maintained >95 % activity over five reuse cycles, with minimal leaching confirmed by ICP-OES. Post-reaction XPS revealed moderate surface modification (Ce 4+ /Ce 3+ and Ni 2+ /Ni 3+ ratios shift) without signs of structural degradation. Kinetic analysis confirmed pseudo-first-order degradation with high rate constants and short half-lives, highlighting their applicability for rapid pharmaceutical mineralization. This study proposes a rational and selective approach for coupling metal doping and 2D conductive interfaces, enabling the scalable design of stable and efficient photocatalysts for PMS-driven advanced oxidation processes (AOPs) in water purification. • A two-step strategy combining metal doping and MXene integration was developed for PMS activation. • CeO₂ and TiO₂ doped with Fe or Ni exhibited enhanced photocatalytic degradation of pharmaceuticals. • MXene-modified composites showed improved charge separation and light absorption. • CeO₂–Ni–MXene achieved >99 % mineralization under UV and ~ 95 % under visible light. • The catalysts show good stability, reusability, and low metal leaching over cycles