Lattice engineering of fluorite CeO2via La substitution: Dual-active centers of oxygen vacancies and Lewis acid sites for enhanced catalytic ozonation.

Fluorite CeO2 is promising for heterogeneous ozonation due to its tunable electronic structures, but its rigid lattice limits defect formation and electron mobility. Herein, we propose a lattice-engineering strategy by substituting La into the framework to form La2Ce2O7 as new catalysts. This substitution induces lattice distortion and generates abundant oxygen vacancies (OVs, 43.4% Oβ on La2Ce2O7vs. 28.4% on CeO2), forming adjacent Lewis acid sites (Ce3+) and OVs as dual active centers. Under optimal conditions, the La2Ce2O7 system reached 91.5% of oxytetracycline (OTC) degradation within 25 min, which is 1.8 and 5.0 times higher than that with CeO2 and sole ozonation, respectively. Total organic carbon removal reaches 85% after 240 min, evidencing deep mineralization. Mechanistic investigations reveal the synergistic interplay: Lewis acid sites initiate O3 adsorption and activation (supported by XPS and radical analysis), while adjacent OVs likely serve as electron transfer sites to accelerate the Ce4+/Ce3+ redox cycle (Ce3+ fraction 42.97% pre- vs. 41.24% post-reaction), thereby enhancing the generation of both surface-bound and free •OH. Moreover, a counterintuitive hydrodynamic effect was uncovered: SO42- suppresses bubble coalescence, reducing average bubble diameter from 1.52 mm to 0.80 mm, increasing specific interfacial area by ∼90% and nearly doubling KLa, thereby overcoming radical scavenging and boosting OTC degradation in saline water. The La2Ce2O7 catalyst maintains >90% OTC removal over 48 h continuous-flow operation, and the treated effluent shows dramatically reduced ecotoxicity (LC50 from 1.12 to >100 mg·L-1). This work establishes a dual-center lattice engineering paradigm, showing that salinity turns a traditional inhibitor into a performance enhancer for treating refractory pharmaceutical wastewater.