Preparation and photocatalytic performance study of dual Z-scheme Bi2Zr2O7/g-C3N4/Ag3PO4 for removal of antibiotics by visible-light.

At present, the high re-combination rate of photogenerated carriers and the low redox capability of the photocatalyst are two factors that severely limit the improvement of photocatalytic performance. Herein, a dual Z-scheme photocatalyst bismuthzirconate/graphitic carbon nitride/silver phosphate (Bi2Zr2O7/g-C3N4/Ag3PO4 (BCA)) was synthesized using a co-precipitation method, and a dual Z-scheme heterojunction photocatalytic system was established to decrease the high re-combination rate of photogenerated carriers and consequently improve the photocatalytic performance. The re-combination of electron-hole pairs (e- and h+) in the valence band (VB) of g-C3N4 increases the redox potential of e- and h+, leading to significant improvements in the redox capability of the photocatalyst and the efficiency of e--h+ separation. As a photosensitizer, Ag3PO4 can enhance the visible light absorption capacity of the photocatalyst. The prepared photocatalyst showed strong stability, which was attributed to the efficient suppression of photo-corrosion of Ag3PO4 by transferring the e- to the VB of g-C3N4. Tetracycline was degraded efficiently by BCA-10% (the BCA with 10 wt.% of AgPO4) under visible light, and the degradation efficiency was up to 86.2%. This study experimentally suggested that the BCA photocatalyst has broad application prospects in removing antibiotic pollution.

Effective mineralization of p-nitrophenol by catalytic ozonation using Ce-substituted La1‒xCexFeO3 catalyst.

In this study, cerium-doped lanthanum ferrite perovskite oxides (La1‒xCexFeO3) with different A-site were synthesized using a sol-gel method and they were used as ozonation catalyst for p-nitrophenol (PNP) mineralization for the first time. Catalytic activity in terms of total organic carbon (TOC) removal followed the order of La0.8Ce0.2FeO3 > La0.4Ce0.6FeO3 > La0.6Ce0.4FeO3 > La0.2Ce0.8FeO3 > LaFeO3 with 77, 66, 61, 60 and 56% respectively. The synthesized catalysts were characterized by diffraction of X-ray (XRD), Raman spectroscopy, Brunauer-Emmett-Teller (BET) and scanning electronic microscopy (SEM). Moreover, electron spin resonance (ESR) and radicals quenching experiments showed that the active oxygen species in the ozone decomposition process are mainly hydroxyl radical (·OH), and also include superoxide radical (O2-) and singlet oxygen (1O2). Furthermore, the superior activity of La0.8Ce0.2FeO3 could be attributed to the higher surface area, the richer lattice oxygen, richer surface -OH groups and the facilitated redox Ce3+/Ce4+ and Fe2+/Fe3+ cycling. In addition, this study provides an insight to use metal-doped perovskite catalysts for catalytic ozonation.