Nitrate adsorption by synthetic activated carbon magnetic nanoparticles: kinetics, isotherms and thermodynamic studies

In this study, synthesized Fe3O4 magnetic nanoparticle (MNP) coated on powder activated carbon was applied for the adsorption of nitrate from aqueous solutions. This novel adsorbent was then characterized by Scanning electron microscopy, Transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscope, and N-2 adsorption-desorption. Effects of variables such as pH, contact time, initial nitrate concentration, adsorbent concentration, and co-existing anions were all evaluated in detail. The adsorption of nitrate fitted best with the Langmuir isotherm (R-2=0.993) and pseudo-second-order kinetic models (R-2=0.998). The equilibrium time and the maximum monolayer capacity (Q(o)) were determined to be 60min and 57.1mg/g, respectively (at pH 3). Thermodynamic studies revealed that the adsorption process of nitrate was spontaneous and endothermic. Moreover, the adsorption of nitrate followed the circumstantial interface in solid/liquid phases. Eventually, the activated carbon-Fe3O4 MNP (AC-Fe3O4 MNP) could be applied as a proper adsorbent for the removal of nitrate from aqueous solutions due to the advantages of high efficiency, rapid separation, and multiple usages.