Synthesis of La and Cr Co-doped BiFeO3 nanoparticles to investigate the magnetic properties and photocatalytic performance

Abstract

Pharmaceutical wastewater contamination, especially from antibiotics, poses significant environ- mental and health hazards due to the emergence of antibiotic-resistant bacteria and the limitations of conventional treatment methods. In this study, BiFeO3-based nanomaterials—10% La-doped Bi90La10FeO3 (BLFO) and 50% Cr-doped BiFe0.5Cr0.5O3 (BFCO)—were synthesized via the sol-gel method and evaluated as visible-light-responsive photocatalysts for the degradation of ciprofloxacin (CIP) and levofloxacin (LFX) under solar irradiation. Structural, morphological, and spectroscopic characterizations confirmed the formation of single-phase perovskite struc- tures with successful La and Cr incorporation, leading to reduced particle sizes, enhanced optical absorption, narrowed band gaps (2.14 eV for BLFO and 1.87 eV for BFCO), and improved charge carrier separation. Notably, La doping significantly enhanced magnetization, likely due to the suppression of the spiral spin cycloid structure in BiFeO3. In BFCO, the presence of oxygen vacancies facilitated efficient charge transfer and promoted reactive oxygen species (ROS) generation, as evidenced by XPS, Raman, and electrochemical (CV, LSV, EIS) analyses. The strong optical absorption of BLFO contributed to enhanced charge separation and ROS generation, achieving ∼70% degradation of pharmaceutical pollutants. BFCO, with its narrower band gap, demonstrated superior solar energy utilization, achieving 70.35% degradation of CIP and 94% of LFX within 240 minutes, following pseudo-first-order kinetics. The activation en- ergy decreased from 33.61 ± 5.88 to 19.69 ± 3.94 kJ mol–1, confirming enhanced photocatalytic performance. An apparent quantum yield (AQY) of 34.9% for LFX further highlighted BFCO’s efficiency. Scavenger studies identified electrons (e–) and superoxide radicals (•O2–) as the dominant ROS responsible for antibiotic degradation, with oxygen vacancies playing a key role in facilitating charge separation and ROS formation. Reusability tests confirmed the structural, morphological, and optical stability of both photocatalysts over multiple cycles. The degradation mechanism involves solar-induced electron–hole pair generation, charge transfer to oxygen vacancies, and subsequent redox reactions that break down antibiotics. The synergistic effects of La and Cr substitution, oxygen vacancies, and mixed-valence states significantly enhanced the photocatalytic activity, highlighting the promise of BLFO and BFCO nanomaterials for scalable environmental remediation applications.