In this study, a novel nanohybrid composite was fabricated via the incorporation of manganese ferrite (MnFe₂O₄) nanoparticles into the integrated surface of reduced graphene oxide (rGO) and black cumin seeds (BC). The nanohybrid composite was prepared by a simple co-precipitation method and characterized by several spectroscopic and microscopic techniques. The characterization analysis revealed that the rGO-BC surface was decorated with the MnFe₂O₄. The strong chemical interaction (via electrostatic and H-bonding) between the integrated surface of rGO-BC and MnFe₂O₄ nanoparticles has been reported. The prepared composite was highly porous with a heterogeneous surface. The average size of the prepared composite was reported in the ranges of 2.6–7.0 nm. The specific surface area of the prepared composite was calculated to be 50.3 m²/g with a pore volume of 0.061 cc/g and a half pore width of 8.4 Å. As well, many functional sites on the nanohybrid composite surface were also found. This results in the excellent adsorption properties of nanohybrid composite and the effectual elimination of methylene blue dye from water. The nanohybrid was tested for various linear isotherms, such as Langmuir and Freundlich, for the adsorption of methylene blue dye. The Freundlich isotherm was the well-fitted model, proving the adsorption is multilayer. The maximum Langmuir adsorption capacity of nanohybrid composite for methylene blue was reported to be 74.627 mg/g at 27 °C. The adsorption kinetics followed the pseudo-second-order recommended surface interaction between the dye and nanohybrid composite. The interaction between methylene blue and the nanohybrid composite was also confirmed from the FTIR spectrum of the methylene blue-loaded adsorbent. The rate-determining step for the present study was intraparticle diffusion. Temperature-dependent studies of methylene blue adsorption were also carried out to estimate adsorption’s free energy, enthalpy, and entropy. The methylene blue adsorption was feasible, spontaneous, and endothermic. A comparison study revealed that the present materials could be successfully prepared and used for wastewater treatment.

This study reports the preparation of a novel hybrid composite and its application in adsorption. For this composite preparation, zirconia (ZrO₂) was precipitated onto an integrated framework of reduced graphene oxide (rGO) and black cumin (BC) seeds. Characterization using Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray analysis, and transmission electron microscopy confirmed the successful incorporation of ZrO₂ nanoparticles (5–20 nm) into the integrated carbon framework of rGO and seed powder. The microscopic analysis further revealed that the ZrO₂ NPs were dispersed throughout the integrated rGO-BC framework. Using the rGO-BC@ZrO₂ composite, methylene blue dye was decontaminated from water through a batch adsorption process. The rGO-BC@ZrO₂ composite achieved 96% MB adsorption at an adsorbent dose of 2.0 g/L, and nearly 100% when the adsorbent concentration was 3.0 g/L. Modeling of the experimental adsorption values was also established to verify the adsorption viability and mechanism. Thermodynamic modeling confirmed the feasibility and spontaneity of the present batch adsorption process. Isotherm modeling, which showed its compatibility with the Freundlich isotherm, suggested multilayer adsorption. rGO-BC@ZrO₂ demonstrated good persistence and reusability for methylene blue for up to five consecutive adsorption cycles. Thus, this study presents optimistic results regarding water purification.