Activities of BiFeO3/carbon-dots catalysts in piezo-photocatalytic degradation of ciprofloxacin upon light/ultrasonic excitation

Enhanced aquatic antibiotic removal via dual piezoelectric photocatalyst CdS/BiFeO3 S-scheme heterojunction: Mechanism, degradation pathway, and toxicity evaluation

Piezo-photocatalysis represents an effective and eco-friendly strategy for water purification, wherein singlet oxygen (1O2) serves as a crucial reactive oxygen species due to its exceptional selectivity and remarkable oxidative capacity in wastewater degradation processes. Herein, we elaborately designed a dual piezoelectric photocatalyst, the Cadmium sulfide/Bismuth ferrite (CdS/BiFeO3) step-scheme (S-scheme) heterojunction to synergistically enhance generation pathways of 1O2 for efficient removal of antibiotic contaminants. In this study, under the combination of ultrasonic vibration and visible light irradiation, the optimized CdS/BiFeO3-10 % exhibited a reaction rate constant of 0.200 min-1 for ciprofloxacin (CIP) degradation, which was 9.52 and 5.88 times higher than that of individual piezocatalysis and photocatalysis, respectively. The synergistic effect of the interfacial electric field and the vibration-induced piezoelectric field significantly promoted charge carrier separation, as supported by detailed experimental and theoretical results. Through quenching experiment and Electron spin resonance (ESR), 1O2 and holes (h+) played major roles in CIP degradation. Furthermore, the toxicity and degradation pathways of CIP intermediates were systematically evaluated. The CdS/BiFeO3 composite also demonstrated outstanding reusability and cycle stability, making it suitable for practical wastewater treatment applications. This work highlights the potential of CdS/BiFeO3 with piezoelectric effect-assisted S-scheme heterojunction for highly efficient antibiotic wastewater remediation, offering a novel and effective strategy for water purification.

Z-scheme p-n Co3O4@FeVO4 heterojunction-assisted peroxymonosulfate activation under visible light for boosted degradation of antibiotics: Enhanced intrinsic electric field and broadened visible-light absorption

Overcoming rapid charge recombination remains a critical challenge in photocatalytic system development. This study reports the successful synthesis of a Z-scheme p-n heterojunction photocatalyst Co3O4@FeVO4 (CF) via hydrothermal treatment followed by high-temperature calcination to optimize the optoelectronic properties of FeVO4. The engineered heterojunction interface established an intrinsic electric field that spatially segregated photogenerated charge carriers, enhancing visible-light absorption (band gap narrowing to 1.78 eV) while suppressing charge recombination. When coupled with peroxymonosulfate (PMS) activation, the CF/PMS system demonstrated exceptional antibiotic removal efficiencies within 120 min: ciprofloxacin (93.6 %), ofloxacin (88.8 %), norfloxacin (90.4 %), and tetracycline (97.1 %). Remarkably, the catalyst maintained stable ciprofloxacin degradation performance across a wide pH range (3-11) in aqueous solutions. Mechanistic investigations revealed dual degradation pathways involving both radical species (SO4·-, ·OH and h+) and non-radical species (1O2 and e-). Ecotoxicity evaluation through E. coli bioassays and computational modeling demonstrated that degradation intermediates exhibited reduced ecological hazards, with significantly lower bioaccumulation factors in aquatic organisms. This work advances the design of Z-scheme heterojunction photocatalysts for PMS-activated antibiotic removal and provides a promising strategy for sustainable water purification.

Er-Doped BiVO4/BiFeO3 Nanocomposites Synthesized via Sonochemical Process and Their Piezo-Photocatalytic Application

In this work, Er-doped BiVO4/BiFeO3 composites are prepared using the sonochemical process with a difference of rare earth loading compositions. The crystallinity and chemical and morphological structure of as-synthesized samples were investigated via X-ray diffraction, Raman scattering, and electron microscopy, respectively. The diffuse reflectance technique was used to extract the optical property and calculate the optical band gap of the composite sample. The piezo-photocatalytic performance was evaluated according to the decomposition of a Rhodamine B organic compound. The decomposition of the organic compound was achieved under ultrasonic bath irradiation combined with light exposure. The Er-doped BiVO4/BiFeO3 composite heterojunction material exhibited significant enhancement of the piezo-photocatalytic activity under both ultrasonic and light irradiation due to the improvement in charge generation and separation. The result indicates that Er dopant strongly affects the phase transformation, change in morphology, and alternation in optical band gap of the BiVO4 matrix. The incorporation of BiFeO3 in the composite form with BiVO4 doped with 1%Er can improve the photocatalytic performance of BiVO4 via piezo-induced charge separation and charge recombination retardment.