Preparation of aminated magnetite / SiO2 / chitosan core-shell nanoparticles for efficient adsorption of nitrate and phosphate anions in water

Magnetite-silica-chitosan-amine nanoparticles were prepared for use as an effective adsorbent for the removal of nitrate and phosphate anions from an aqueous solution. The physical and chemical properties of the prepared composite were investigated by Fourier transform infrared (FT-IR), vibrating sample magnetometry (VSM), Brunauer, Emmett & Teller (BET) surface analysis, transmission electron microscopy (TEM), X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), and zeta potential measurement. The adsorption parameters of nitrate and phosphate anions on the prepared adsorbent were studied to optimise their removal process, and the results obtained revealed that the adsorption reached equilibrium after 60 and 90 min for nitrate and phosphate respectively. The best adsorption capacities of nitrate and phosphate were found to be 112.5 mg.g(-1) at pH6 for nitrate and 89.95 mg.g(-1) at pH5-6. The isothermal adsorption results clearly show that the adsorption process of nitrate and phosphate anions by Fe3O4/SiO2/Cs-NH2 nanoparticles can be described by the Langmuir isotherm model, and therefore the adsorption involved physisorption. Desorption studies showed that 87.6% of the nitrate and 81.5% of the phosphate were recovered in less than 90 min using a NaOH solution (0.25 M). These results suggest great potential for the use of magnetite-chitosan-amine for the removal of nitrate and phosphate anions.