Facile preparation of a novel modified biochar-based supramolecular self-assembled g-C3N4 for enhanced visible light photocatalytic degradation of phenanthrene

The rational design of a novel and environmentally friendly photocatalytic composite for persistent pollutant removal, energy production and catalytic applications have attracted widespread interest. In this study, the new composite composed of KOH-modified biochar and g-C₃N₄ with different morphologies was successfully prepared with facile supramolecular self-assembly and thermal poly-condensation method. The characterization results of the as-prepared composites suggested that KOH-modified biochar had been well combined with g-C₃N₄ with different morphologies. These synthesized catalysts were used to degrade phenanthrene under visible light radiation. A-BC/g-C₃N₄-D performed best and removed 76.72% phenanthrene. Its first-order reaction rate constant was 0.355 h^-1, which was 3.7 times higher than that of g-C₃N₄. A-BC/g-C₃N₄-D still exhibited a high photocatalytic activity after four cycles. Radical quenching results showed that superoxide radical (·O₂^-), hydroxyl radical (·OH) and hole (h⁺) could be used as active species in the redox reaction with phenanthrene. Based on the exploration results of gas chromatography-mass spectrometer (GC-MS), a possible reaction pathway of phenanthrene degradation was also proposed. This study provides a novel strategy for fabricating various high-performance photocatalysts and the removal of persistent organic pollutants.

Preparation of CuSe-PDA/g-C3N4 and its visible-light photocatalytic performance to dye degradation

CuSe as an excellent photocatalytic semiconductor material has wildly used in the field of photocatalysis. In this paper, CuSe-PDA/g-C₃N₄ was designed and synthesized, and the photocatalytic performance of CuSe was further enhanced by the addition of polydopamine (PDA) and graphite phase carbon nitride (g-C₃N₄). The as-prepared CuSe-PDA/g-C₃N₄ was characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), and elemental mapping. The specific surface area and porous characteristics of the material were also studied by N₂ adsorption-desorption isotherm, which the specific surface area were 186.6 m²/g and pore size were of 3.1 nm by BET data analysis. The photocatalytic conditions for the degradation of methylene blue (MB) by CuSe-PDA/g-C₃N₄ were optimized in the experiment. The results showed that the photocatalytic performance of CuSe-PDA/g-C₃N₄ under visible-light illumination were better than CuSe and PDA owing to the narrow band gap energy and delayed electron-hole recombination. Under the optimized conditions, the removal rate reach to 99% of 50 mg/L MB within 60 min irradiation time. Moreover, the MB removal rate was over 90% through six repeated experiments, which proved that the CuSe-PDA/g-C₃N₄ composite nanomaterials have good stability and reusability.