Synthesis and characterization of magnetic mesoporous silica nanoparticles for Ba2+ removal from aqueous media

According to the World Health Organization1, the maximum limit of barium in drinking water is 0,7 mg.L-1. Magnetic nanoparticles are potential candidates for removing Ba2+ ions due to their high adsorption capacity, easy separation for magnetic field and low cost synthesis2. In this work, we have synthesized magnetic mesoporous silica nanoparticles (Fe3O4@SiO2), using previously described methodology2. The material was characterized by FTIR, TGA, DRX, and TEM, which enhanced images are showed in figure 1. The left image shows magnetite spherical particles having an average diameter of 7,5 nm, while the right image shows bigger aggregates with 13,8 nm, due to the magnetite´s coated process with silica. For Ba2+ removal, it was performed experiments using 5 mL of 5 ppm of barium solutions in contact with 100 mg of Fe3O4@SiO2 for 5, 15, 30, 60, 90 and 120 minutes. The barium concentration was then determined by UV-vis spectroscopy following the formation of the complex between the Ba2+ and sulfonazo III ion at  = 580 nm (Figure 2). The linearized model of pseudo-second order for kinetic adsorption3 can be described by equation 1. where QT e Qe are the amounts of adsorbate adsorbed per gram of the adsorbent (mg.g-1) at time “T” and at equilibrium respectively. K2 is the pseudo-second order rate constant (g.mg-1.min-1), and can be obtained from the slope of the graph of figure 3, which showed a correlation coefficient R2 = 0,99937.