Fabrication of highly dispersed platinum-deposited porous g-C3N4 by a simple in situ photoreduction strategy and their excellent visible light photocatalytic activity toward aqueous 4-fluorophenol degradation

Treatment of fluorine-containing pharmaceutical wastewater by VUV/UV process

As an advanced oxidation process, vacuum ultraviolet/ultraviolet (VUV/UV) has been intensively studied for drinking water treatment, but assessment of its feasibility for wastewater treatment has rarely been conducted. This study investigated the treatment of fluorine-containing pharmaceutical wastewater by VUV/UV process and examined the defluorination and therefore the improvement of biodegradability of the wastewater after the process. The results indicated that the degradation of a model fluorine-containing organic compound (namely, 4-fluorophenol) was mainly achieved via the attack of the fluorine atom linking directly to the aromatic ring by the HO^• generated from VUV photolysis of water. As the solution pH increased from 4.0 to 10.0, the COD removal efficiency of the real pharmaceutical wastewater decreased slightly from 18.1 to 15.9%, while the release ratio of F^- increased from 50.8 to 75.5%. As the dissolved oxygen increased from 0.15 to 12 mg L^-1, the removal efficiency of COD and the release ratio of F^- increased from 9.2 to 17.1% and from 48.2 to 75.5%, respectively. The biodegradability index (BOD/COD) increased significantly from 0.24 to 0.47 after the VUV/UV irradiation, which confirmed the feasibility of applying the VUV/UV process for improving biodegradability of the pharmaceutical wastewater.

Enhanced 4-FP removal with MnFe2O4 catalysts under dielectric barrier discharge plasma: Economical synthesis, catalytic performance and degradation mechanism

The dielectric barrier discharge plasma (DBDP) process has received extensive attention for the removal of organic contaminants from water. A novel microwave-assisted hydrothermal method was used to easily and rapidly synthesize MnFe₂O₄ catalysts. Based on the DBDP process, MnFe₂O₄ can enhance 4-fluorophenol (4-FP) abatement from 44.15% to 58.78% through the catalysis within 18 min. Then, the adjunction of O₃ generated by discharge can further boost 4-FP degradation to 94.94%. After the whole optimization process is complete, the associated pseudo-first-order reaction kinetic constant and energy efficiency were enhanced from 0.0327 to 0.1536 min^-1 and 2067.13 mg kW h^-1 to 4444.75 mg kW h^-1, respectively. With the help of the condition, blank and radical capture experiments, the catalytic performance caused by MnFe₂O₄ and O₃ was attributed to the joint action of Fenton-like reactions, photocatalysis (ultraviolet, UV), photoassisted Fenton reactions and O₃ catalysis. The overall downward trend of the possible intermediate toxicities indicated that the DBDP/MnFe₂O₄/O₃ process can effectively remove and mineralize 4-FP without the generation of more toxic intermediates. In addition, during the 5 cycles, MnFe₂O₄ can maintain excellent recovery, efficiency and durability. In summary, the coupling of discharge plasma and MnFe₂O₄ sheds new light on catalysis for wastewater treatment.

Palladium nanoparticles supported on exfoliated g-C3N4 as efficient catalysts for selective oxidation of benzyl alcohol by molecular oxygen

Palladium catalysts supported on exfoliated g-C₃N₄ materials demonstrate high catalytic activity in selective oxidation of benzyl alcohol using ambient oxygen as an oxidant.

Continuous Flow Synthesis of High Valuable N-Heterocycles via Catalytic Conversion of Levulinic Acid

Graphitic carbon nitride (g-C₃N₄) was successfully functionalized with a low platinum loading to give rise to an effective and stable catalytic material. The synthesized g-C₃N₄/Pt was fully characterized by XRD, N₂ physisorption, XPS, SEM-Mapping, and TEM techniques. Remarkably, XPS analysis revealed that Pt was in a dominant metallic state. In addition, XPS together with XRD and N₂ physisorption measurements indicated that the g-C₃N₄ preserves its native structure after the platinum deposition process. g-C₃N₄/Pt was applied to the catalytic conversion of levulinic acid to N-heterocycles under continuous flow conditions. Reaction parameters (temperature, pressure, and concentration of levulinic acid) were studied using 3 levels for each parameter, and the best conditions were employed for the analysis of the catalyst's stability. The catalytic system displayed high selectivity to 1-ethyl-5-methylpyrrolidin-2-one and outstanding stability after 3 h of reaction.

M/g-C3N4 (M=Ag, Au, and Pd) composite: synthesis via sunlight photodeposition and application towards the degradation of bisphenol A

In this work, natural sunlight successfully induced the deposition of gold (Au), silver (Ag), and palladium (Pd) nanoparticles (NPs) with 17.10, 9.07, and 12.70 wt% onto the surface of graphitic carbon nitride (g-C₃N₄). The photocatalytic evaluation was carried out by adopting Bisphenol A (BPA) as a pollutant under natural sunlight irradiation. The presence of noble metals was confirmed by EDX, HRTEM, and XPS analysis. The deposition of Ag NPs (7.9 nm) resulted in the degradation rate which was 2.15-fold higher than pure g-C₃N₄ due to its relatively small particle size, contributing to superior charge separation efficiency. Au/g-C₃N₄ unveiled inferior photoactivity because the LSPR phenomenon provided two pathways for electron transfer between Au NPs and g-C₃N₄ further diminished the performance. The improved degradation lies crucially on the particle size and Schottky barrier formation at the interface of M/g-C₃N₄ (M=Au, Ag, and Pd) but not the visible light harvesting properties. The mechanism insight revealed the holes (h⁺) and superoxide radical (^•O₂^-) radical actively involved in photocatalytic reaction for all composites.