Comparative removal of acid orange 7 and aniline onto mesoporous graphene oxide-nickel ferrite magnetic nanocomposites in batch adsorption and application of conventional kinetic and isotherm models

This study investigates the efficiency of graphene oxide nickel ferrite (GO-NiFe₂O₄) nanocomposites for removing acid orange 7 (AO7) dye and aniline (B-NH₂) from aqueous solutions. Initially, GO was synthesized from graphite powder using Tour’s method. Subsequently, GO-NiFe₂O₄ nanocomposites were prepared via co-precipitation and hydrothermal methods. The synthesized materials go through comprehensive characterization using SEM, EDX, XRD, FT-IR spectroscopy, BET, and TGA analysis. The pH of point of zero charge (pHpzc) for GO was determined to be 6, while for GO-NiFe₂O₄ nanocomposites, it was found to be 7.2 using the salt addition method. The adsorption of AO7 and B-NH₂ onto GO-NiFe₂O₄ nanocomposites was studied under various experimental conditions: solution pH, adsorbent dose, contact time, initial concentration, temperature, and in the presence of electrolytes. Kinetic studies revealed that the pseudo-second-order model provided the best fit for both AO7 and B-NH₂ adsorption processes, with correlation coefficients exceeding 0.99. Equilibrium data were well-described by the Langmuir isotherm model, showing maximum monolayer adsorption capacities (q_m) of 344.8 mg g⁻¹ for AO7 and 294.1 mg g⁻¹ for B-NH₂. Thermodynamic analysis indicated that the adsorption of AO7 was endothermic (∆H⁰ > 0), while B-NH₂ adsorption was exothermic (∆H⁰ < 0). Negative ∆G⁰ values and positive ∆S⁰ values confirmed the spontaneity and increased disorderliness of the adsorption processes. Furthermore, the GO-NiFe₂O₄ nanocomposites demonstrated effective regeneration and reusability over five consecutive cycles, highlighting their potential as efficient adsorbents for AO7 and B-NH₂ removal from wastewater.