Designing advanced nanocomposite materials for efficient elimination of Victoria Blue B dye from aqueous media

The growing discharge of persistent cationic dyes necessitates adsorbents that combine high efficiency, facile production, and reliable regeneration. Herein, nickel oxide/magnesium chromate/carbon novel nanocomposites were successfully synthesized by a Pechini sol-gel route at 600 and 800 °C to obtain NMC600 and NMC800, respectively, for the elimination of Victoria Blue B from aqueous media. XRD, FE-SEM, HR-TEM, EDX, and BET analyses confirmed the formation of well-integrated nanostructures whose physicochemical properties were strongly governed by calcination temperature. NMC600 displayed smaller crystallites, finer polyhedral particles, higher residual carbon content, larger surface area (56.27 m²/g), and greater pore volume (0.2517 cm³/g), resulting in marked superior adsorption performance compared with NMC800. Under optimized conditions, NMC600 achieved a maximum Langmuir capacity of 371.74 mg/g, whereas NMC800 reached 194.55 mg/g. Kinetic evaluation revealed that dye uptake followed the pseudo-first-order model, while thermodynamic parameters confirmed a spontaneous, exothermic, and predominantly physical adsorption process. Mechanistic interpretation indicated that electrostatic attraction under alkaline conditions, hydrogen bonding, complexation, and π-π interaction collectively controlled dye removal. The nanocomposites also exhibited efficient desorption using 2 M HCl, stable recyclability over five cycles, resistance to common interfering ions, and promising performance in real wastewater.