Nitrogen-phosphorus codoped biochar prepared from tannic acid for degradation of trace antibiotics in wastewater

This study was designed to develop a one-step pyrolysis process that could efficiently activate peroxymonosulfate (PMS) and degrade tetracycline hydrochloride (TCH) by producing N, and P codoped carbon materials (NPTC3-800). Furthermore, it exhibited a high specific surface area (658 cm2 g-1), a larger pore volume (0.3 cm3 g-1), and a certain content of heteroatoms (nitrogen and phosphorus). PMS-activated NPTC3-800 attained a TCH removal efficiency of over 90% within 40 min, with an observed rate constant (kobs) of 0.0307 min-1. Similarly, the materials exhibited strong resistance to ionic interferences and showed broad applicability across various water bodies. Mobility experiments were conducted to further assess the stability of catalyst (92%, 40 h). Non-radical oxidation pathways, particularly including the singlet oxygen (1O2), were evidenced to play dominant roles in TCH degradation, as demonstrated by electron paramagnetic resonance (EPR) observations and experiments with free radical quenching. Theoretical calculations demonstrated that the N and P codoped domains substantially improve TCH removal compared to pure biochar. Finally, the proposed degradation pathways for TCH were identified, and the resulting degradation products demonstrated reduced biological toxicity.

Degradation of tetracycline via peroxymonosulfate activation by highly reusable Titanium dioxide/impregnated Zirconium-chitosan beads

The nano-sized powder photocatalysts are prone to agglomeration and poor reusability, which cause secondary pollution. To avoid the loss of powder photocatalyst, Titanium dioxide/(TiO2)/impregnated Zirconium (Zr)-chitosan beads were prepared using a simple cross-linking reaction for the peroxymonosulfate activation to aid the tetracycline degradation. The beads' structural, morphological and optical properties were studied using different techniques. The prepared catalysts effectively degraded 97% of tetracycline (10 mg/L) in 20 min of visible light illumination. The sulfate radicals, superoxide radicals, holes and singlet oxygen were found to be the predominant reactive groups that boosted the tetracycline degradation. The key intermediates were analyzed, and the degradation pathway of tetracycline was proposed. The reusable microspheres exhibited maximum reusability up to 10 cycles with an 11% loss in degradation efficiency. Overall, the important advantages of photocatalytic 3D beads include higher reusability, minimal catalytic mass loss during recovery process and stronger visible light utilization via band gap alteration, opening a new horizon toward effective wastewater management.

Strategies for improving the stability of perovskite for photocatalysis: A review of recent progress

Photocatalysis is currently a hot research field, which provides promising processes to produce green energy sources and other useful products, thus eventually benefiting carbon emission reduction and leading to a low-carbon future. The development and application of stable and efficient photocatalytic materials is one of the main technical bottlenecks in the field of photocatalysis. Perovskite has excellent performance in the fields of photocatalytic hydrogen evolution reaction (HER), oxygen evolution reaction (OER), carbon dioxide reduction reaction (CO2RR), organic synthesis and pollutant degradation due to its unique structure, flexibility and resulting excellent photoelectric and catalytic properties. The stability problems caused by perovskite's susceptibility to environmental influences hinder its further application in the field of photocatalysis. Therefore, this paper innovatively summarizes and analyzes the existing methods and strategies to improve the stability of perovskite in the field of photocatalysis. Specifically, (i) component engineering, (ii) morphological control, (iii) hybridization and encapsulation are thought to improve the stability of perovskites while improving photocatalytic efficiency. Finally, the challenges and prospects of perovskite photocatalysts are discussed, which provides constructive thinking for the potential application of perovskite photocatalysts.

Efficient Photocatalytic Degradation of Tetracycline on the MnFe2O4/BGA Composite under Visible Light

In this work, the MnFe₂O₄/BGA (boron-doped graphene aerogel) composite prepared via the solvothermal method is applied as a photocatalyst to the degradation of tetracycline in the presence of peroxymonosulfate. The composite's phase composition, morphology, valence state of elements, defect and pore structure were analyzed by XRD, SEM/TEM, XPS, Raman scattering and N₂ adsorption-desorption isotherms, respectively. Under the radiation of visible light, the experimental parameters, including the ratio of BGA to MnFe₂O₄, the dosages of MnFe₂O₄/BGA and PMS, and the initial pH and tetracycline concentration were optimized in line with the degradation of tetracycline. Under the optimized conditions, the degradation rate of tetracycline reached 92.15% within 60 min, whereas the degradation rate constant on MnFe₂O₄/BGA remained 4.1 × 10^-2 min^-1, which was 1.93 and 1.56 times of those on BGA and MnFe₂O₄, respectively. The largely enhanced photocatalytic activity of the MnFe₂O₄/BGA composite over MnFe₂O₄ and BGA could be ascribed to the formation of type I heterojunction on the interfaces of BGA and MnFe₂O₄, which leads to the efficient transfer and separation of photogenerated charge carriers. Transient photocurrent response and electrochemical impedance spectroscopy tests offered solid support to this assumption. In line with the active species trapping experiments, SO₄^•- and O₂^•- radicals are confirmed to play crucial roles in the rapid and efficient degradation of tetracycline, and accordingly, a photodegradation mechanism for the degradation of tetracycline on MnFe₂O₄/BGA is proposed.