Adsorption of Congo Red from aqueous solution using doped strontium hexaferrite – zero valent iron nanocomposite: Kinetic, isotherm, and thermodynamic studies

Abstract

In this study, doped strontium hexaferrite / zero-valent iron nanocomposite (SrFe₁₂O₁₉/nZVI) was synthesized and its adsorption ability for removing Congo Red (CR) dye from aqueous solution was evaluated. Fourier transform infrared spectroscopy (FT-IR), Scanning electron microscopy (SEM), and X-ray diffraction analysis (XRD) were used to characterize the adsorbent. Experimental conditions, including pH, initial concentration of pollutant, adsorbent weight, contact time, and temperature were optimized. Maximum removal efficiency was achieved at pH of 8.5, initial concentration of CR=20 μg mL^-1, adsorbent weight of 0.12 g, contact time=15 min and temperature of 25ºC. The results of isotherms showed that Langmuir isotherm was suitable for describing CR adsorption with R²=0.9959. Also, kinetic models were investigated, and the data followed the pseudo-second order kinetic model with R²=0.9969. In addition, thermodynamic parameters were evaluated.