Efficient photocatalytic degradation of indigo carmine dye by CoFe2O4@g-C3N4 nanocomposite

Semiconductor-based photocatalysts are potential candidates for efficiently controlling pollution and reducing noxious organic contaminants from wastewater. The present research is devoted to fabricating a semiconducting nanocomposite material for the photodegradation of indigo carmine (IC) as a model organic pollutant. A facile eco-friendly method was adopted to synthesize cobalt ferrite nanoparticles (CoFe₂O₄) from their precursors using Pimpinella anisum extract as a reducing and capping agent and then coupled to graphitic carbon nitride (g-C₃N₄) to achieve CoFe₂O₄@g-C₃N₄ composite. X-ray diffraction analysis confirmed the formation of both phases in the composite, with a mean crystallite size (≈29 nm) for CoFe₂O₄. In contrast, the chemical composition obtained by EDS and XPS techniques revealed the presence of Co, Fe, O, C, and N. Consequently, the CoFe₂O₄@g-C₃N₄ heterostructure reduced the indirect band gap from 2.82 to 2.33 eV, thereby improving visible-light absorption. The optical band gap of pure CoFe nanoparticles was found to be ∼3.20 eV, which is more direct and increases the surface area to ≈59 cm². g⁻¹. The CoFe₂O₄, g-C₃N₄, and CoFe₂O₄@g-C₃N₄ were tested for the degradation of the IC under visible light illumination. The nanocomposite exhibits excellent photocatalytic performance towards the IC degradation, reaching 100 % within 60 min. The synergism of CoFe₂O₄ and g-C₃N₄ within the CoFe₂O₄@g-C₃N₄ heterostructure resulted in a lessened energy band gap, hindered electron/hole pair recombination, and improved both electrons and holes viability for the photodegradation through the formation of active radicals, and consequently an enhancement of dye photodegradation.