Functionalized magnetic nanoparticles Fe3O4@SiO2@PTA (PTA = (2-pyrimidylthio)acetic acid) for efficient removal of mercury from water

Abstract Functionalized magnetic nanoparticles were prepared by anchoring (2-pyrimidylthio)acetic acid on to the surface of the silica coated Fe3O4 (Fe3O4@SiO2) nanoparticles by acid amide coupling reaction. These nanoparticles were characterized on the basis of powder-XRD, FTIR, FESEM, HRTEM and EDX analysis. The adsorption property of these functionalized nanoparticles (Fe3O4@SiO2@PTA) was investigated in water with a large number of metal ions and anions, which revealed that it selectively adsorbs Hg2+ with high efficiency (920 mg/g). The desorption of Hg2+ from Fe3O4@SiO2@PTA-Hg2+ was successfully carried out with the aid of EDTA and the process was repeated three times successfully to examine its reusability. The adsorption of Hg2+ was also investigated with the variation of pH in the range 2 to 8 and maximum adsorption was noted at the pH 7.0. Detail study on adsorption suggests that out of the two adsorption isotherm models, Langmuir and Freundlich, the former one (Langmuir) fits better in this case. Detail kinetic study on the adsorption process was also carried out and the data fitted with both the two semi-empirical kinetic models, pseudo-first-order and pseudo-second order, out of which the pseudo second-order model exhibited excellent fitting with correlation coefficient R2 = 0.99 for all concentrations of Hg2+. Finally, on the basis of experimental data, the mechanism for interaction of Hg2+ with Fe3O4@SiO2@PTA nanoparticle is discussed.