Synthesis of polyaniline/Fe3O4 magnetic nanoparticles for removal of reactive red 198 from textile waste water: kinetic, isotherm, and thermodynamic studies

In this study, polyaniline/Fe3O4 (PAni/Fe3O4) magnetic nanoparticles were synthesized and used as an adsorbent for the removal of Reactive Red 198 (RR 198) from water. Scanning electron microscope was used for determining morphology and size distribution of the prepared nanoparticles. The size of magnetic nanoparticles Fe3O4 was characterized by Transmission Electron Microscope. The formation of magnetic nanoparticles Fe3O4, was confirmed through X-ray Diffraction Technique. The chemical structures of the products were investigated with Fourier transform infrared spectroscopy. Effective parameters on the removal of RR 198 such as pH, dosage, and time were investigated and optimized. At the optimum situations the pH, dosage, and time were 5, 0.8g l–1, and 90 min, respectively. For determining the type of adsorption isotherm, Temkin, Langmuir, and Freundlich adsorption isotherms were used. The results revealed that Langmuir isotherm adequately met the experimental requirements. According to the Langmuir model, PAni/Fe3O4 magnetic nanoparticles sorbents exhibited the highest RR 198dye adsorption capacity of 45.454 mg g−1. Kinetic analyses were conducted using pseudo-first and second-order models and the regression results showed that the adsorption kinetics was more accurately represented by the pseudo-second-order model. Thermodynamic parameters such as changes in Gibbs free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) were calculated. The negative values of ΔG° and the positive value of ΔH° (257.068KJ/mol) and ΔS° (104.590 J/mol K) show that the RR 198 adsorption on PAni/Fe3O4 magnetic nanoparticles was a spontaneous and endothermic process.