Visible-light photocatalytic water purification using g-C3N4-modified NiFe2O4/K2Fe4O7 ferrite nanoceramics

Abstract

Developing efficient and reusable photocatalysts responsive to visible light is important for advanced wastewater treatment. In this study, a novel ternary nanocomposite composed of graphitic carbon nitride (g-C₃N₄), nickel ferrite (NiFe₂O₄, NFO), and potassium ferrate (K₂Fe₄O₇, KFO) was synthesized via simple wet-impregnation method. This multifunctional nanocomposite was thoroughly characterized using XRD, FTIR, SEM, EDX, XPS, BET/BJH, UV–Vis DRS, PL, and VSM to assess its structural, morphological, textural, magnetic, and optical properties. The g-C₃N₄/NFO/KFO composite exhibited superior photocatalytic activity under visible-light irradiation, achieving 98.57 % degradation of methylene blue (MB) with rate constant of 0.0537 min⁻¹ and retaining over 94 % efficiency after five reuse cycles. A direct Z-scheme charge transfer mechanism was confirmed, enabling efficient separation of photogenerated charge carriers and enhancing reactive oxygen species (ROS) generation. Key parameters affecting photocatalytic performance were systematically studied. Alkaline conditions (pH 10) favored dye adsorption and ROS formation, resulting in near-complete degradation (99.94 %), while acidic pH hindered activity due to surface protonation and suppressed •OH production. Lower dye concentrations (10 mg/L) allowed optimal light penetration and access to active sites, whereas higher concentrations caused inner filter effects and reduced efficiency. Increasing photocatalyst dosage improved degradation by enhancing the availability of active sites and ROS, with optimal performance at 0.06–0.08 g/L. Moreover, the composite maintained high activity across different water sources, including lake, tap, and distilled water, demonstrating robustness in practical environments. These findings underscore the synergistic behavior of the composite components and highlight the g-C₃N₄/NFO/KFO nanocomposite as a promising visible-light-driven photocatalyst for real-world wastewater remediation.