Citric acid coated magnetic nanoparticles: Synthesis, characterization and application in removal of Cd(II) ions from aqueous solution

Citric acid coated magnetite nanoparticles (Fe3O4-Cit) have been synthesized for the removal of cadmium from aqueous solutions. As-prepared Fe3O4-Cit was characterized by using Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometer (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) and through the determination of pHzpc. Several factors effecting the adsorption of Cd(II) ions on the surface of Fe3O4-Cit such as pH, temperature and contact time were investigated. The Cd(II) ions adsorption equilibrium on the Fe3O4-Cit were obtained by 35 min at the optimized pH 5. Kinetic study shows the Cd(II) adsorption onto Fe3O4-Cit follow the pseudo-second order kinetic model with R2 > 0.997 at 308 K. The adsorption data was satisfactorily explained by Langmuir and Freundlich isotherm models. The experimental data found to be suitable linearity with Langmuir isotherm having maximum adsorption capacity (qm) values in mg g−1 10.81, 11.45 and 12.56 at the 298 K, 303 K and 308 K, respectively. The correlation coefficient R2 = 0.997 fully supports the favorability of Langmuir isotherm in adsorption process. The negative values of ΔG°, −5.68, −6.31 and −6.95 kJ mol−l throughout the temperature at 298 K, 303 K and 308 K are indicating the feasibility of adsorption process on to Fe3O4-Cit was spontaneous in nature.