A 1D/2D Bi2O3/g-C3N4 step-scheme photocatalyst to activate peroxymonosulfate for the removal of tetracycline hydrochloride: insight into the mechanism, reactive sites, degradation pathway and ecotoxicity.

A novel 1D/2D step-scheme Bi2O3/g-C3N4 was prepared using a simple reflux method. Bi2O3 photocatalysts showed lower photocatalytic activity for the degradation of tetracycline hydrochloride under visible light irradiation. After compositing with g-C3N4, the photocatalytic activity of Bi2O3 was enhanced obviously. The enhanced photocatalytic activity of the Bi2O3/g-C3N4 photocatalysts could be attributed to the high separation efficiency of carriers generated by the Bi2O3/g-C3N4 photocatalyst due to the formation of a step-scheme heterojunction, which inhibited the recombination of photogenerated electrons and holes. In order to further enhance the degradation efficiency of tetracycline hydrochloride, Bi2O3/g-C3N4 was used to activate peroxymonosulfate under visible-light irradiation. The influences of peroxymonosulfate dosage, pH value and tetracycline hydrochloride concentration on activating peroxymonosulfate to degrade tetracycline hydrochloride were investigated in detail. The mechanism of Bi2O3/g-C3N4 activating peroxymonosulfate was proved by radical quenching experiments and electron paramagnetic resonance analysis, which proved that the sulfate radical and hole dominated the degradation of tetracycline hydrochloride. The possible vulnerable sites and pathways of tetracycline hydrochloride were predicted via DFT calculations based on Fukui function and UPLC-MS. Toxicity Estimation Software predicts that the degradation processes of tetracycline hydrochloride could gradually reduce toxicity. This study could provide an efficient and green method for the subsequent treatment of antibiotic wastewater.

Synthesis of a ternary Bi2O3/CQDs/rGO photocatalyst to active peroxymonosulfate for the removal of tetracycline hydrochloride.

In this paper, the ternary Bi2O3/CQDs/rGO photocatalyst was synthesized by a solvothermal method. The as-fabricated Bi2O3/CQDs/rGO composites showed stronger visible-light response and higher photocatalytic activity. In order to further enhance the degradation efficiency of tetracycline hydrochloride, Bi2O3/CQDs/rGO was used to activate peroxymonosulfate under visible-light irradiation. The degradation efficiency increased sevenfold, indicating that the synergistic effect of photocatalysis and peroxymonosulfate activated by photogenerated electrons could clearly increase the degradation efficiency of tetracycline hydrochloride. In addition, the photocatalytic mechanism was further proposed and verified by radical quenching experiments and electron paramagnetic resonance analysis. Thus, this study provides a new idea for the photocatalytic application of Bi2O3/CQDs/rGO and a contribution to the degradation of antibiotics to avoid polluting the water environment.

Efficient degradation of VOCs using semi-coke activated carbon loaded ternary Z-scheme heterojunction photocatalyst BiVO4-BiPO4-g-C3N4 under visible light irradiation.

The coal chemical industry generates large amounts of solid waste and volatile organic compounds (VOCs). In this study, the solid waste semi-coke powder obtained in the semi-coke production process was used as a raw material to prepare high-specific surface area semi-coke activated carbon (SAC) by a carbonization and activation process, and a ternary z-scheme heterojunction photocatalyst with high catalytic performance was loaded for synergistic treatment by adsorption and photodegradation to achieve waste treatment with waste. The prepared semi-coke activated carbon has a specific surface area of 619.27 m2 g-1, which can achieve effective adsorption of VOCs. The ternary z-scheme heterojunction photocatalyst BiPO4-BiVO4-g-C3N4 (PVCN) was supported on a semi-coke activated carbon substrate by a one-step sol-gel method. Based on the synergistic effect of adsorption and photocatalysis, the obtained PVCN/SAC material can degrade toluene by 85.6% within 130 minutes under simulated sunlight irradiation, which is 2.43 times that of pure photocatalyst. The rate of degrading toluene can be increased by 4.43 times. Capture experiments showed that superoxide radicals (˙O2-) and hydroxyl radicals (˙OH) were the key active species in the degradation pathway. Even after five cycles, the material maintained 81.6% of the degradation performance. In this work, we deeply investigate the mechanism of semi-coke activated carbon as a matrix for enhancing photocatalytic degradation performance. The findings of this work provide new insights into the efficient degradation of VOCs and provide a good theoretical basis for the development of high-performance photocatalysts.

Synergetic effect of photocatalysis and peroxymonosulfate activated by MFe2O4 (M = Co, Mn, or Zn) for enhanced photocatalytic activity under visible light irradiation.

Nanosized MFe2O4 (M = Co, Mn, or Zn) photocatalysts were synthesized via a simple sol-gel method. MFe2O4 photocatalysts exhibited lower photocatalytic activity for the degradation of levofloxacin hydrochloride under visible light irradiation. For enhancement of photocatalytic activity, MFe2O4 was used to activate peroxymonosulfate and degrade levofloxacin hydrochloride under visible light irradiation. The influences of peroxymonosulfate dosage, levofloxacin hydrochloride concentration, pH value, and temperature on peroxymonosulfate activation to degrade levofloxacin hydrochloride were investigated in detail. The mechanism of activation of peroxymonosulfate by MFe2O4 was proposed and proved by radical quenching experiments, electron spin resonance analysis, X-ray photoelectron spectroscopy, electrochemical impedance spectroscopy, and transient photocurrent responses. The combined activation effects of photogenerated e-/h+ and transition metals on peroxymonosulfate to produce sulfate radical clearly enhanced the degradation efficiency.